942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
WWR Helps Aggregate InterlockWhen a slab cracks, the faces within the crack arejagged. If the sections on each side of the crack areheld closely together, the jagged faces of the concreteare interlocked which helps transfer loads across thecrack. This factor is called aggregate interlock. As thecrack becomes wider the interlock between the faces ofthe crack decreases and becomes less effective. Inresidential and light construction, aggregate interlock isusually ineffective when the crack width exceeds 1/16in. (0.06”). Welded wire reinforcement holds the cracksclosely together so that aggregate interlock will functionproperly. Closely knit cracks are also less noticeable,and they minimize the movement of water through theslabs at cracks.
Welded Wire Reinforcement (WWR) Widely UsedLiterally millions of square feet of residentialslabs, driveways, sidewalks, patios and slabsfor light construction are reinforced with weldedwire reinforcement (WWR). Welded wire rein-forcement must be properly placed if it is to per-form effectively. This publication will briefly dis-cuss the reasons for using welded wire reinforcement, its benefits and how to place it properly.
WWR Used To Control CrackingConcrete by its very nature tends to crack. In residential and light construction, cracking is due primarily to drying shrinkage, temperatureand moisture changes, weak subgrades andsometimes poor quality concrete. Steps can betaken to reduce cracking while other procedures control cracking. The primary purpose of welded wire reinforcement inslabs is to control cracking and crack width-inboth directions. Welded wire reinforcementkeeps the cracked sections of a slab closely knittogether so that the slab will act as a unit.
Welded wire reinforcement should be placed 1/3 the depth from top of slab. Welded wire reinforcement puts more strength in your concrete.
TF 202-R-03
How To Specify, Order & Use Welded WireReinforcement In Light Construction
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 2 • TF 202-R-03
Some Thoughts for Builders About Welded WireReinforcementProbably every builder has at one time or anothersaid, ”If I eliminate the welded wire reinforcement, I’llsave some money,” or someone might have said,“Take out the WWR and add another inch of concrete,it’s cheaper.” Someone else might have said, “Thestuff stays down on the bottom and doesn’t do muchgood.” Let’s critically look at these statements.
Proper Placement is EssentialWelded wire reinforcement should be placed in themiddle one third of a 4 to 6 inch thick concrete slabor driveway. WWR, partially buried in the subgrade,has little value. The reinforcement should be placedto reinforce the concrete, not the subgrade. Whenwelded wire reinforcement is properly placed, itdoes its job and does it well.
Thicker Slabs vs. ReinforcementThis argument frequently arises but it overlooks threekey points about cracking:
• Most cracks formed in residential and light construction are due to drying shrinkage and temperature changes.
• Both four and five inch slabs will contract the same amount due to drying shrinkage, and will contract equally as the temperature drops.
• Thickening the slab does not change shrinkage and temperature contraction and reinforcement is still needed.
The material cost of reinforcement is almost alwaysless than the material cost of extra concrete. As amatter of fact, the “in-place” cost of welded wirereinforcement may be less than the material cost ofan extra inch of concrete and the WWR reinforcesthe entire slab. For example, the material cost of aninch of concrete per square foot is $0.15-0.18 whenconcrete reinforcement used is small. Two widelyused styles of reinforcement used in residential andlight construction are 6x6 W1.4 x W1.4 (10 gauge)and 6x6 W2.9 x W2.9 (6 gauge). These sheets ofWWR only weigh 0.21 lb and 0.42 lb per squarefoot respectively. We suggest that you compare totalcosts. A reinforced slab may cost the same or lessthan a slightly thicker unreinforced slab and there isa difference.
Some Additional Reasons to Use WWRThe main purpose of reinforcement is crack control.Crack control is important in a residence. A home is generally a family’s largest investment and is a source of great pride. Concrete slabs with cracks or uneven surfaces are a matter of no little concern to homeowners.The proper placement of welded wire reinforcement inslabs will go a long way in reducing this concern.
WWR Reinforcement will:• Improve performance of concrete work which
means higher owner satisfaction.
• Reduce or even eliminate callbacks for repairs by dissatisfied customers.
• Make compliance with NAHB’s Home Owners Warranty (H.O.W.) provisions easier because of improved crack control. H.O.W. requires repairs when cracks exceed limits of H.O.W.’s Performance Standards (see Table 1).
• Require fewer joints. The only practical way to control cracking in plain concrete is to use joints at very close intervals – generally less than 15 ft. apart. Joints are acceptable in sidewalks and driveways. Joints are not particularly desirable in floor slabs, porches, carports and garages. Welded wire reinforcement reduces the need for many joints in these slabs.
Table 1* Provisions Home Owners Warranty Program on
Cracking of Concrete
* Published by Home Owners Warranty Corporation, NationalHousing Center, Washington, D.C. 20005
Maximum Permissible
Crack Width
1/8”
3/16”
1/4”
Hairline only (less 1/16”)
1/4”
Maximum Permissible
Vertical Displacement
–
*1/8”
1/4”
–
1/4”
Any crack which significantly impairsappearance or performance of the finishflooring material is not acceptable.
C.I.P. basement walls
Basement floors
Attached garage slabs
Stoops and steps
Patios
Slab-on-grade
Performance Standard
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 3 • TF 202-R-03
Various supports for welded wire reinforcement. Place supports 2-3 feet apart for proper positioning of welded wire reinforcement duringconcrete placing. Concrete block, wire or plastic supports to hold reinforcement. These units are economical and effective.
Proper PlacementThe proper placement of welded wire reinforcementis relatively simple and inexpensive. There is noacceptable reason for its improper placement.Welded wire reinforcement should be placed in themiddle third of 4 to 6 inch slabs. Two inches below thesurface is recommended in most cases.
The most common ways of placing WWR are:(1)chairing WWR, (2)placing concrete in two courses and placing WWR on the first course.
Chairs or concrete blocks cost very l itt le.Reinforcement is placed in a slab primarily to controlcracking. When considering the cost of concrete,reinforcement, and vapor barriers, the cost ensuringproper placement is a small, but important, part.Properly placed WWR can make a tremendous difference in slab performance–and for only cents persquare foot. Depressing or “walking-in” WWR and“hooking” WWR are not methods of placement. Neither method is considered accurate for proper placement.
Chairing WWRThe most widely used method is to chair or supportWWR. A number of concrete accessory suppliers sellchairs and supports for this purpose. The supportsare usually steel wires or plastic units and shouldhave a solid base so they will not sink into the sub-grade or subbase. Base plates are particularly impor-tant when a sand subbase is placed over the sub-grade. The chair or support should not puncture thevapor barrier if one is used. Small concrete blockswith an imbedded wire or grooved on top are used forsupports and require no base plates. These are themost economical and effective way to bolster weldedwire reinforcement for slabs on grade. A very simplechair or support is simply a piece of concrete 2 or 3inches thick and about 4 x 4 inches square. Manyother styles of supports are available and effective.The important part is the use of support to achieve
proper placement within the slab. The spacing willdepend upon the wire size and the wire spacing.Common practice is to place supports 2 to 3 feet apart.
Placing WWR in Two-Course WorkThis is usually the most effective way of placingWWR. It does require more time. The first course ofconcrete is placed generally to mid-depth or perhapsslightly more. The WWR is then placed and the sec-ond course should be placed before the lower coursestarts to harden to prevent formation of a “cold” jointbetween the courses.
Table 2
Proper Location of WWR in SlabLocation of WWR
Middle of slab2” below top surface2” below top surface
Slab Thickness
4”5”6”
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 4 • TF 202-R-03
WWR is sold in rolls or sheets. Roll width varies in thearea where it is sold and is generally 5 to 7 ft. Rolllength is normally 150 or 200 ft. Rolls or sheets areeasy to haul and store.
The biggest advantage of sheets is the fact that thereis no need to unroll and straighten the WWR. Sheetsare thus easier to place and give better placement con-trol. Sheets are commonly 5 to 10 feet wide and 10 to20 feet long. Also, 25 foot sheet lengths are commonand available from stock in the Western, USA. Othersizes are available. In other instances, WWR is pro-duced specifically for an individual job or project.
When specifying non-stock items, the volume must besufficient to justify production at an economical cost. Inmany instances the WWR producer must draw wire toproduce special orders. In addition, the machine mustbe stopped and the wires changed for the next orderof WWR. Quantity requirements vary with differentproducers.
Generally, a minimum quantity of 40,000 lb. isrequired to produce a special order involving a majorchange, such as a change in longitudinal wire size orspacing. The minimum quantity on minor changesinvolving the same size longitudinal wire is consider-ably less. Minor changes might be a change in size orspacing of transverse wires, length of side or endoverhangs, or length changes.
The production of WWR has a facet similar to precastproduction or the use of forms in cast-in-place work –the greater the repetition the less the cost It is there-fore urged that a minimal number of styles be used formaximum economy, thus saving on the cost of WWR.Equally important, fewer styles reduce on-site or in-plant costs, since there are fewer pieces to inventoryand handle, ensuring quality control.
STYLE OF WWR TO USE
Slab thickness and the distance between walls or designjoints primarily determine the style of WWR to use. Thusas slabs become longer ( or thicker) they require heavierWWR.
Minimum Reinforcement Determined(As developed by the traditional subgrade dragmethod used in slab and pavement design)*
Table 3 gives the Minimum Reinforcement for 4-InchThick Lightly Reinforced Slabs-on-Ground. The max-imum dimensions in table 4 refer to the distancebetween design joints, between walls or between ajoint and a wall.
* Subgrade drag theory is explained on page 21 of the PortlandCement Association publication entitled “Concrete Floors onGround”, Second Edition.
Intermediate Control JointsIntermediate control (or contraction) joints can beformed or sawcut in concrete reinforced with WWRfor additional crack control. Sidewalks and drivewayswhich are sometimes quite long should have controljoints. The WWR continues across the control jointand is very helpful in the control of vertical displace-ment due to the dowelling action of the WWR. Forheavier styles of WWR it may be necessary to cut 1/3to 1/2 of the wires to guarantee full depth crack control.
How to Specify and Order Welded Wire ReinforcementWelded wire reinforcement is a prefabricated reinforcingmaterial, and thus the method of specifying and orderingit is different from other types of reinforcement. It is avail-able in both rolls and sheets. Some styles of WWR arecommonly stocked by WWR producers, supply houses, dis-tributors and fabricators. Table 4 lists many of the common-ly stocked items.
Table 3Requirements for 4-Inch Thick Lightly Reinforced
Slab-On-GroundMaximum
Dimension Style Of WWR
Up to 35 ft.
36 ft. to 45 ft.
46 ft. to 60 ft.
61 ft. to 75 ft.
76 ft. to 100 ft.
6 x 6 W1.4 x W1.4
6 x 6 W2.0 x W2.0
6 x 6 W2.5 x W2.5
6 x 6 W2.9 x W2.9 or6 x 6 W3.0 x W3.0
6 x 6 W4.0 x W4.0
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 5 • TF 202-R-03
Wire Size DesignationIn 1970 ASTM changed from the gauge system to a more rational numbering system which relates to thecross-sectional area of the wire. The new numbering sys-tem was designed to simplify the use of welded wire rein-forcement. The designation of wire sizes by gauges givesno pertinent information such as diameter or cross-sec-tional area. In addition, the cross-sectional area of mostgauges are given in complex numbers. i.e., 2gauge=0.054sq. in., 2/0 gauge=0.086 sq. in. (both incross-sectional areas). It is also difficult to relate gaugesand cross-sectional areas, and this often requires frequentreference to tables.
The current system involves a letter-number combina-tion. ASTM uses the letter “W” to designate smooth wire
and the letter “D” to designatedeformed wire. The number followingthe letters “W” or “D” gives the cross-sectional area of the wire in hun-dredths of a square inch. Forinstance, a W5.0 is a smooth wirewith a cross-sectional area of 0.05sq. in. A W5.7 wire has a cross- sec-tional area of 0.057 sq. in. D6.0would indicate a deformed wire witha cross-sectional area of 0.06 sq. in.
WWR should be specified using the“W” or “D” numbers designationrather than gauge number. Table 7
gives a comparison between the gauges and the “W”and “D” numbers. There are four widely used styles ofWWR namely 4-, 6-, 8-, and 10-gauge.
SpecificationsThe American Society for Testing and Materials publishes specifications for the wire used to manufac-ture WWR for both smooth and deformed welded wirereinforcement . The Canadian Standards Associationpublishes similar standards for use in Canada. Thecorresponding titles and numbers are given in Table 5.These are considered to be the governing specifica-tions for both wire and welded wire reinforcement.Some governmental agencies have special specifica-tions which will control if cited.
Minimum StrengthsWelded wire reinforcement is a high strength reinforce-ment material. The minimum yield strength for smoothwelded wire reinforcement is 65,000 psi.
The minimum yield strength of deformed welded wirereinforcement is 70,000 psi. Higher yield strengths upto 80,000 psi are available. See Table 6 for minimumproperties of steel wires.
Welded Smooth Wire ReinforcementThere are two types of wire, plain (or smooth) anddeformed. Plain WWR develops anchorage of the steelat the welded intersections. In plain WWR the smallerwire should have a cross-sectional area equal to atleast 40 percent of the area of the larger wire. ASTMspecifies a weld shear strength of 35,000 psi times thearea of the larger wire.
Welded Deformed Wire ReinforcementDeformed wire has two or more lines of deformationsalong the wire depending on the size of the wire.Anchorage is developed along the wire by virtue of thedeformations and at the welded intersections. Indeformed WWR the smaller wire should have at least 40percent of the cross-sectional area of the larger wire.The weld shear strength for deformed WWR is 35,000psi times the area of the larger wire.
New Designation(by W-Number)
Old Designation(by Steel Wire Gauge) Longit. Trans.
It is preferred that these wires be ordered by the prop-er W-number. The current numbering system makes itextremely easy for the designer. For instance, if a steelcross-sectional area of 0.15 sq. in. per lin. ft. is need-ed, it can be met with W5 wires on 4-in. centers (3wires pr lin. ft. each with a cross- sectional area of0.05 sq. in.).
Designating Style of WWRWelded wire reinforcement is designated by two num-bers and two letter-number combinations. An example
is 6x8 – W8 x W4. The first number gives the spacing ininches of the longitudinal wires. The seond number givesthe spacing of the transverse wires in inches. The firstletter-number combination gives the type and size of thelongitudinal wire, and the second combination givesinformation on the transverse wire. Thus, in the aboveexample the longi- tudinal wires are 6 in. apart while thetransverse wires are 8 in. apart. The longitudinal wire isplain and has a cross-sectional area of 0.08 sq. in. whilethe transverse wire is also plain and has an area of 0.04sq. in.
Longitudinal wire spacings vary. Typical spacings are2,3,4,6,8,12,16,18, and 24 in. The concrete pipe usesconsiderable welded wire reinforcement with 2 in. and 3 in. spacings. Most building, paving and structural rein-forcement have 4 in. through 18 in. longitudinal wire spacings.
Transverse wire spacings are normally 4,6,8,12, 16 and 18 in. It is possible to order other wire spacings butthese will normally cover most situations.
Other DimensionsEnd overhangs, unless otherwise specified, are one-halfof the transverse wire spacing, For instance, a 6x6 rein-forcement would have a 3 in. overhang on each end.Specific lengths of end overhangs can be specified.
Table 6ASTM and CSA Minimum Properties of Steel
Wires in Welded Wire Reinforcement
Type of WWRMin. Tensile
Strength (psi)
Min. YieldStrength
(psi)
Weld Shear
Strength
*Yield strength is measured at 0.005 inch per inch extension of gage length
Welded PlainWire Reinforcement
Welded DeformedWire Reinforcement
75,000
80,000
65,000
70,000
35,000
35,000
W45W31W30W28W26W24W22W20
W18
W16
W14
W12W11W10.5
W10W9.5W9
D45D31D30D28D26D24D22D20
D18
D16
D14
D12D11
D10
D9
W8.5W8W7.5
W7W6.5
W6W5.5
W5
W4.5W4W3.5
W3W2.9W2.5
W2
W1.4
D8
D7
D6
D5
D4
Deformed
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 7 • TF 202-R-03
However, the sum of both end overhangs should equalthe transverse wire spacing. The length of a WWR roll orsheet is the tip-to-tip length and includes the end over-hangs. Length is usually expressed in feet.
Side overhangs will not be furnished unless specified.ASTM does permit an overhang up to 1 inch on eachside. An example of how to specify a side overhangmight be +1 +3 designation which indicates a 1 inchoverhang on one side and a 3 inch overhang on theopposite side. The width of WWR is the center-to-cen-ter distance between the outside longitudinal wires andis expressed in inches. The overall width includes sideoverhangs and is the tip-to-tip length of the transversewires.
Information on OrderingCertain information is needed when ordering. Theexample on this page illustrates how a typical order ofwelded wire reinforcement might appear using thenomen-clature described.
Calculating WeightsThe calculation of welded wire reinforcement weightsis relatively simple. Use the following formula to findweight of both longitudinal and transverse wires.
wt-number wires* x length in feet x area of wire in sq. in. x 3.4
*No. of longitudinal wires = ( width, in. ) +1
longitudinal wirespacing, in.
*No. of transverse wires = length, in.
transverse wirespacing, in.
When using sheets, it is often easier to determineweight of sheet and then convert to weight per100 sq. ft.
For example, what is weight of 8 x 20 ft. sheets of6x12-W12xW5 with no side overhangs.
Longitudinal wires:20 transverse wiresx 8 ft. x 0.05 x 3.4 = 27.2 lb.
Weight of sheets = 165.9 lb.
Weight per 100 sq. ft. = 100/8x20 x wt. sheetWeight of 165.9 = 103.7 lb. per 100 sq. ft.
Example of Typical OrderItem
123
Quantity
1000 Sheets150 Rolls
500 Sheets
Style
6x12 - W12xW56x6 - W2xW24x8 - D10xD4
Width
96”96”76”
SideOverhangs
(+0”, +0”)(+0”, +0”)(+2”, +6”)
OverallWidth
969684
Length
20’ - 0”150’ - 0”17’ - 4”
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Concrete Shrinks with Age–A Cause of CrackingConcrete has its greatest volume when it is first placedin the forms. As it sets, it starts to contract or shrink, Theshrinkage process continues for several years. It is estimated, however, that 60% to 70% of the shrink-age will occur by the time the concrete is three to six months old.
Shrinkage varies with many factors, such as amount of mixing water and cement used, type of aggregate,humidity and slump. In plain concrete, the drying shrink-age varies from 1/2 to 1 inch per 100 ft. Assuming anaverage shrinkage of 3/4 in.per 100 ft., a 30’ x 60’ slabwould shrink or contract slightly over 1/5 inch in the 30 ft.dimension, and 0.45 or almost 1/2 inch in the long direc-tion. If a plain (unreinforced) slab is not divided by joints,it will almost always crack. If there are, for instance, onlyone or two cracks, they may become entirely too wide forsatisfactory performance.
Subgrade Settlement and Loads – A Cause of CrackingThe subgrade (or subbase, if one is used) must provideuniform support for the slab. If uniform support is notprovided, loads may cause the slab to crack and onesection could drop considerably below the other – a con-dition referred to as vertical displacement.This problem is often observed in residential work. It is due to two factors – the crack opens too wide foraggregate interlock to act and the support by the sub-grade is not uniform causing uneven settlement of thesubgrade. Loads such as vehicles on a drivewayincrease the problem.
The use of sound fill material, careful placement of fillmaterials and adequate compaction are important. This is especially true of the area over trenches exca-vated for utility lines. Many builders place a double layerof WWR over the trenched area. This provides addition-al structural strength. Subgrades inside foundation wallsare difficult to fill and compact adequately. Excessivemoisture under slabs also reduces support.
The loads on residential and light slabs are usually notheavy enough to cause a problem. Point loads, such asbearing walls or fireplaces, may sometimes necessitatespecial design. Driveways, garage and carport slabs,and sidewalks where they cross driveways are general-ly exposed to the severest loads. However, a faulty sub-grade or unusual load or the combination of both cancause severe cracking problems.
Temperature Changes Affect Concrete–A Cause of CrackingAs the temperature increases, a slab expands and as thetemperature drops, it contracts. Since there is rela-tively little temperature change within a house, temper-ature may have little effect on interior slabs. Temperaturedoes, however, affect exterior concrete, such as side-walks, driveways and porches, carport and patio slabs.The effects of temperature changes must be consideredin the construction of garage slabs, unheated buildingsand outside flatwork. A drop of 100 degrees F, in temper-ature will cause a contraction of approximately 2/3 inchper 100 ft. A temperature drop of 50 degrees, F, say from80 degrees to 30 degrees, will cause a contraction of 1/3inch per 100 ft.
Drying shrinkage and temperature contraction are inde-pendent of each other. If a slab contracts 3/4 inch per 100ft. from drying shrinkage, it will contract or expand addi-tionally for temperature changes. Thus the total contrac-tion on a cold day is considerable, often causing cracksto open up excessively in unreinforced concrete.
SummaryThe Benefits of Welded Wire Reinforcement Are:• Holds cracked sections closely together enabling
slab to act as a unit through effective aggregateinterlock action. Aggregate interlock decreasesrapidly as crack width exceeds 1/16 inch.
• Maintains level, even surface so one cracked section willnot drop below the other which often happens when a widecrack develops on a weak subgrade.
• Adds some structural strength to slabs althoughamount of steel is small. The use of WWR will normally reduce number of cracks.
• Permits larger panels and thus fewer joints.• Improves appearance of slab by holding cracks together.
Page 8 • TF 202-R-03
Length (or Width)
* For 100∞ F difference, increase contraction 1/3; for a 50∞difference, subract 1/3 temperature contraction value.
30 ft..23”
.15”
.38”
40 ft..30”
.20”
.50”
50 ft..38”
.25”
.63”
60 ft..45”
.30”
.75”
75 ft..56”
.37”
.93”
100 ft..75”
.50”
1.25”
Contraction due todrying shrinkage atrate of 3/4” per 100’
Contraction due totemperature drop of 75° F*
Total contraction
Table 8Slab Contraction Due to Drying Shrinkage and
a Temperature Change of 75 Degrees, F
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
5.1.I When tested as described in Test Methods and Definitions A37O,the material, except as specified in 6.1.2, shall conform to the tensileproperty requirements in Table 1 (Table 2 for A496) based on nominalarea of wire.
5.1.2 (8.1.2) The yield strength shall be determined as described in TestMethods and Definitions A370 at an extension of 0.5% in./in. of gagelength.The manufacturer is not required to test for yield strength but isresponsible for supplying a product that will meet the stipulated limitwhen tested in conformance with the provisions of 11.3 (13.3 for A496).For determining the yield strength, use a Class B-1 extensometer asdescribed in Practice E83.The extensometer should be removed fromthe specimen after the yield strength has been determined.
5.1.3 (8.1.3) For material to be used in the fabrication of welded wirereinforcement, the tensile and yield strength properties shall conform tothe requirements given in Table 2 (Table 3 for A496), based on nomi-nal area of the wire.
5.1.4 (8.1.4) The material shall not exhibit a definite yield point as evi-denced by a distinct drop of the beam or halt in the gage of the test-ing machine prior to reaching ultimate tensile load.The purchaser mayopt to accept this feature as sufficient evidence of compliance with thespecified minimum yield strength tests covered in 11.3 (13.3 for A496).
5.2 (8.2) Bend Test - The bend (or wrap test - see A370, A4.7.I ,.2,.3) testspecimen shall stand being bent at room temperature through 180°with-out cracking on the outside of the bent portion as described in Table 3.
5.3 Reduction of Area Test - The reduction of area shall be determinedas described in Test Methods and Definitions A370, and the wire shallconform to the reduction of area requirements in Table I and Table 2(Tables 2 & 3 for A496).
10. (12) Number of Tests
One tension and one bend test shall be made from each 10 tons (9070kg) or less of each size of wire or fraction thereof in a lot, or a total ofseven samples, whichever is less.A lot shall consist of all the coils of asingle size offered for delivery at the same time.
A370, 5. I The Tension test related to the mechanical testingof steel products subjects a machined or full-section specimenof the material under examination to a measured load sufficientto cause rupture.The resulting properties sought are defined inTerminology E6.A370, 13.2 Yield Strength is the stress at which a materialexhibits a specified limiting deviation from the proportionalityof stress to strain. The deviation is expressed in terms of strain,percent offset, total extension under load, etc. Determinemethod by “Extension under load.”
11.3 (13.3) If the purchaser considers it desirable to determinecompliance with the yield strength requirements in 5.1 (8.1.3),yield strength tests may be made in a recognized laboratory,or their representative may make the test at the mill if suchtests do not interfere unnecessarily with themill operations.
TABLE 2 - Tension Test Requirements (Material for Welded Wire Reinforcement) • A82Size Wl.2 Smaller than
TABLE 3 - Bend Test Requirements • A82Size Number of Wire Bend TestW7 and smaller Bend around a pin the diameter that is equal to the
diameter of the specimenCoarser than W7 Bend around a pin the diameter that is equal to twice the
diameter of the specimen
TABLE 5 - Bend Test Requirements • A496Size Number of Wire Bend TestD-6 and smaller Bend around a pin the diameter that is equal to twice
the diameter of the specimenCoarser than D-6 Bend around a pin the diameter that is equal to four
times the diameter of the specimen
A370, A4.7.1 The wrap test is used as a means for testing theductilty of wire.
A4.7.2 The test consists of coiling the wire in a closely spacedhelix tightly against a mandrel of a specified diameter for arequired number of turns. (Unless other specified, the requirednumber of turns shall be five). The wrapping may be done byhand or a power devise. The wrapping rate may not exceed 15turns per minute. The mandrel diameter shall be specified inthe relevant wire product specification.
ASTM Welded Wire Reinforcement Test Data for Quality AssuranceUse of this guide—The left side includes test data that exists in the latest ASTM standards.The right side has referenced tables from thelatest ASTM standards and data from A370-A4 and 11.4 as well as industry comments.
ASTM A82 & A496 Plain and Deformed Wire Test Data[Note: A496 deviations are in () when different from A82]
7.1 Tensile – Wire for the production of welded wire reinforcement isdescribed in Specification A82.Tensile tests may be made on wire cutfrom the welded wire reinforcement and tested either across orbetween the welds; no less than 50% shall be across welds. Tensiletests across a weld shall have the welded joint located approximatelyat the center of the wire being tested and the cross wire forming thewelded joint shall extend approximately 1 in.(25mm) beyond each sideof the welded joint.
Note 3 – Tensile, reduction of area and bend testing are normally doneat the time the wire is drawn.The manufacturer’s finished product stillmust satisfy the mechanical properties when tested after fabrication.
7.2 Reduction of Area (A185 only)—The ruptured section of the tensilespecimen is measured to determine this property.In the case of a spec-imen which has been tested across a weld, the measurement shall bemade only when rupture has occurred at a distance from the center ofa weld to permit an accurate measurement of the fractured section.Thewire shall meet the minimum reduction of area requirements ofSpecification A82.
7.3 Bend Test – The wire shall withstand the bend test as described inSpecification A82 (or A496) and shall be performed on a specimentaken from between the welds.
7.4 Weld Shear Strength – The weld shear strength between longitudi-nal and transverse wires shall be tested as described in Section 11.Theminimum average shear value in pounds-force shall not be less than35,000 multiplied by the nominal area of the larger wire in square inch-es (or in Newtons, shall not be less than 241, multiplied by the nominalarea in square millimeters), where the smaller wire is less than sizeW1.2 (not less than a D4 for A497) and has an area of 40% or moreof the area of the larger wire.
7.3.1 (A497) Reinforcement having a relationship of larger and smallerwires other than that covered in 7.3 shall meet an average weld shearstrength requirement of not less than 3.6kN (800 pounds- force) pro-vided that the smaller wire is not smaller than D4.
7.4.4 The material shall be deemed to conform to the requirements forweld shear strength if the average of the four samples complies with thevalue stipulated in 7.4 (or 7.3).If the average fails to meet the prescribedvalue, all the welds across the specimen shall then be tested.The rein-forcement will be acceptable if the average of all weld shear test valuesacross the specimen meets the prescribed minimum value.
11.(8) Weld Shear Test Apparatus and Methods11.1 (8.1) As the welds in welded wire reinforcement contribute to thebonding and anchorage value of the wires in concrete, it is imperativethat the weld acceptance tests be made in a jig that will stress the weldin a manner similar to which it is stressed in concrete.In order to accom-plish this the vertical wire in the jig must be stressed in an axis close toits centerline. Also the horizontal wire must be held closely to the verti-cal wire, and in the same relative position, so as to prevent rotation ofthe horizontal wire. When the reinforcement is designed with differentwire sizes, the larger diameter wire is the “vertical wire” when tested(see Fig.1).
11.2 (8.2) Figure 1 shows the details of a typical testing jig together withtwo anvils which make it possible to test welds for wire up to 5/8” inchin diameter.
11.3 (8.3) Refer to the Standards of proper placement of samples in theweld tester and the maximum load for the rate of stressing. Refer toA370, 7.4 in this publication for the minimum rate of stressing.
10. (12) Number of Tests10.1 (12.1) One test for conformance to tensile strength and bend
requirements shall be made for each 75,000 ft2 (6968 m2) of reinforce-ment or remaining fraction thereof.
10.2 (12.2) One test for conformance to weld shear strength require-ment shall be made for each 300,000 ft2 (27 870 m2) or remaining frac-tion thereof.
A4.7.3 The wire tested shall be considered to have failed if the wire frac-tures or if any longitudinal or transverse cracks develop which can beseen by the unaided eye after the first complete turn.Wire which fails inthe first turn shall be retested, as such fractures may be caused bybending the wire to a radius less than specified when the test starts.
A370, A4.5 Reduction of Area Test—The ends of the fractured speci-men shall be carefully fitted together and the dimensions of the small-est cross section measured to the nearest 0.001 inches (0.025mm)with a pointed micrometer.The difference between the area thus foundand the area of the original cross section, expressed as a percentageof the original area, is the reduction of area.
A370, 7.4 Speed of Testing—The speed of testing shall not be greaterthan that at which load and strain readings can be made accurately.
7.4.1 Any convenient speed of testing may be used up to 1/2 the spec-ified yield point or yield strength. If the machine is equipped with adevice to indicate the rate of loading, the speed of the machine fromhalf the specified yield strength through the yield strength may beadjusted so that the rate of stressing does not exceed 100,000 psi (690MPa) or a minimum of 10,000 psi (70 MPa) per-minute.
WRI CommentMany use a rate of 40,000 psi per minute with success.
WRI Comment
All welded wire reinforcement shall pass weld-shear testing to ensure complete and quality welding.
General CommentSince 1996, ASTM A82, A185, A496 and A497 have included a sup-plement. The supplement refers to high strength wire and weldedwire. Building codes, for example, ACI 318, permit the use of rein-forcement with a yield strength up to 550 MPa (80,000 psi).
WRI CommentThe WRI Industry and Associate members are dedicated to provid-ing quality control and assurance that all products are tested andmeet latest Codes and Standards before material leaves the plants.Institute members have a vast knowledge of manufacturing capabil-ities to helpengineers,fabricatorsand con-tractorsrefinedesigns onan individ-ual projectbasis.
ASTM A185 & A497 Welded Wire Reinforcement Test Data[Note: A497 deviations are in () when different from A185]
��������������������������������������������
Vertical Wire
Horizontal Wire
A A
Section A-A
Page 2 • TF 203-R-03
FIG. 1 Welded Wire ReinforcementWeld Tester
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
The popularity of site cast precast wall panels betterknown as tilt-up panels, like that of almost all otherforms of precast concrete, has increased greatly inrecent years. They are not only durable and economicalbut offer almost endless possibilities for interesting andattractive appearances. These can be obtained byusing various combinations of exposed aggregate,concrete produced from different cements or withadmixed colors, surface treatment, patterned forms,raised or depressed moldings, and they may be insu-lated-referred to as sandwich panels. Panels may beused structurally as well as architecturally in load-bear-ing and non-load-bearing (or curtain) walls, both exteri-or (where they are exposed to wind pressure) and inte-rior (static and suction pressure). They may also have tobe designed to resist earthquake and other naturalforces.
The panels may be pierced by window, door, utility, orornamental openings, or they may have solid surfaces.They are generally very wide although they may be rel-atively narrow members which serve as mullions orform ribs in decorative arrangements. The cross-sec-tion is usually solid, although it may be cored to reduceweight or formed in sandwich fashion around insula-tion.
Tilt-up wall panels are distinguished from other forms ofprecast units since they are cast at the job site ratherthan cast at a precast concrete manufacturing plant.The basic procedure involves casting the members ona horizontal surface, usually a floor slab, and liftingthem into a vertical position to form the building wall.
While once considered a rather new construction sys-tem and generally thought of only in connection withone-story buildings, it is actually several decades oldand has been used in many multi-story structures. Thename tilt-up is derived from methods employed in ear-lier examples. The panels were cast on finished floorslabs with their lower ends Lying along the edge of thebuilding. They were then lifted by the upper end andrevolved about the lower end into a vertical plane; theywere thus tilted up directly into final position. However,as panel sizes were increased it became desirable todo the lifting at points other than the upper portion.Today, most tilt-up panels are cast face down (exteriorside down). The panel inserts are designed by insert
manufacturers and are cast in the face up (interior side).Braces are attached after curing and the panel is rotat-ed into position. Tilt-up construction has come a longway technologically from where it began many yearsago. It can be used for anything from a one-story build-ing up to a four or five story building. There are certainadvantages that make the tilt-up procedure economicalin a variety of circumstances.
One of these may be the very absence of the largeplant; it is frequently claimed that the lack of a sizeableinvestment in fixed facilities is one of the things thatmake tilt-up work feasible. Shipping costs are almostalways lower, as it is cheaper to move raw materialsrather than finished products. The panels require lesshandling and there is less danger of damage. Ordinarilytilt-up panels are cast as required and therefore no stor-age problems arise. The expense of bottom forms iseliminated since the wall units are cast on a floor slab.It may be necessary to require more careful finishing ofslabs than normal to achieve desired wall finishes.
Perhaps the most important feature is reduction orelimination of size restrictions. Since most plant-castmembers must be moved by truck, their width is gen-erally limited to about 8’0””, although sometimes widershipments can be arranged. Maximum weights andlengths are also regulated by law, and extremely longand heavy pieces, unless prestressed, may requireelaborate and expensive precautions to avoid breakagein transit. Permissible size and weight may also be gov-erned by handling equipment in the plant or at the site.
However, for the panel cast at the site these are minorproblems. Width and length can be of any convenientdimension up to the maximum weight that can beraised with lifting equipment. Greater thicknesses andweights may be required and this, too, is of less con-cern with site casting.
Welded Wire Reinforced Tilt-up Panels
TF 204-R-03
Flat andcurved tilt-upwall panelsmake up thefacade of thisOhio project
While some tilt-up panels have been prestressed, byfar the greater portion of them have been of mild rein-forced design. The reinforcement will perform severalimportant functions:
1. To prevent damage due to lifting and handlingstresses.
2. To increase the resistance of the surface to crack-ing because of shrinkage and temperaturechanges.
3. To assist in carrying the vertical loads as bearingwalls.
4. To resist wind, earthquake, and other lateralforces. Welded wire reinforcement (WWR), withhigh strength wires accurately spaced, is well suit-ed for all of these uses.
The action of precast panels is similar to that of otherreinforced concrete members, and their design is verymuch like that of cast-in-place walls. Three kinds offorces must be considered; horizontal or wind andseismic forces, the weight of the member, and theforces received from the roof load in a load bearing sit-uation. Stresses induced when lifting the panel areresisted by the panel inserts, usually no additional rein-forcement is necessary for those stresses.
A complete discussion of the design of tilt-up panels isbeyond the scope of this brochure. High strength weld-ed wire reinforcement with yield strength, fy up to80,000 psi is a viable and cost-effective reinforcementmaterial. Spacings of 3” to 16” can be provided withwire sizes up to D20 (1/2” diameter). More readily avail-able WWR can be specified when spacings are 4” or 6”and wire sizes are less than D12 (3/8”). It is recom-mended to refer to ACI 551R on Tilt-Up ConcreteStructures for a more complete review of methods andprocedures. It may be of interest to use the followingchecklist (Ref. ACI 551R) when preparing design docu-ments.
Checklist when preparing architectural/engineeringproject drawings:
Elevations – Exterior architectural elevations showingpanel dimensions, jointing, openings, areas of special
treatment such as facing aggregates, reveals, formliners, and scuppers.
Details – Architectural details showing bevels, miters,chamfers, tapered recesses, door and window condi-tions, roofing, and flashing connections.
Panel elevation – Panel elevations drawn from theviewpoint of the fabricator (will panel be cast face upor face down) showing typical reinforcement and spe-cial reinforcement at major and minor openings.Recommended scale 1/8 in. = 1 ft. and with each paneluniquely numbered.
Key plan – Key plan to indicate location of panels andpanel designation.
Structural details – Structural details showing typicalthickness (is facing aggregate and grout or architec-tural relief included in the structural thickness) andspecial thicknesses and widths of pilasters.
Reinforcement – Reinforcement details showing typi-cal placement and clear cover requirements, pilasterreinforcement and tie configurations and welded wirereinforcement or rebar dowels for slab connection.
Miscellaneous details – Other items include necessi-ty for mechanical and electrical coordination of open-ings, sleeves, conduits, and junction boxes.
Specifications – Specifications should include thespecified compressive strength of concrete at 28days, design yield strength of reinforcement, minimumstrength, and density of concrete at time of lift, andallowable lift stresses. Requirements, if considerednecessary, of a sample panel to include finishes,miters, corners, and other details.
Shop drawings – The contractor should be requiredto submit shop drawings which depict each panel.
An engineering feature to consider is the usual practiceof making some allowance for impact. This can bereduced by careful handling, preventing bond by usinga bond breaker or breaking by horizontal movement.
A more significant consideration is tensile stress on theouter face of the concrete. As in any reinforced con-crete member, cracks develop when the applied forcesincrease to a point where the ultimate tensile strengthof the concrete is exceeded. Additional load increasemay widen the cracks. This effect must not be allowed
Flat wall panels,cast on the floor
slab, had beentilted into position
before workbegan on the
curved panels.
Page 2 • TF 204-R-03
www.wirereinforcementinstitute.org
to cause permanent damage to the member. It isextremely difficult to compute with any certainty thewidth of cracks that will form or to know what size can betolerated. Any restriction in this respect must usually bebased on judgement and experience; however, the shorttime during which maximum stresses will occur indicatesthat there is less likelihood of trouble due to crack dam-age. Because the bending moment drop off as the panelis tilted, stresses will decrease and cracks will close.Note: reinforced concrete is elastic over a considerablerange. For wall reinforcement welded wire reinforcementprovides a superior type of reinforcement; it is not onlyeffective in carrying tensile stresses but it will also mini-mize shrinkage cracks and control crack widths.
An additional provision found in most building codes isone governing the minimum amount of steel required inwalls. The American Concrete Institute’s “Building CodeRequirements for Reinforced Concrete” (ACI 318)requires in Sections 14.3 and 21.5.2 that:
“Minimum ratio of vertical reinforcement area to gross con-crete area shall be no less than 0.0012 for welded wire rein-forcement (plain or deformed). Minimum ratio of horizontalreinforcement area to gross concrete area shall be 0.0020 forwelded wire fabric (plain or deformed). For seismic, the min-imum ratios (ρv) for shear walls is 0.0025 for both longitudi-nal and transverse reinforcement.”
The larger figure for horizontal steel is justified becausethe length of a wall between points of support or controljoints is generally more than its height and there is agreater possibility of cracking in that direction because ofshrinkage and temperature change.
Table 1 gives minimum vertical and horizontal steel areasrequired by the ACI Building Code for walls from 4” to 8”in thickness, using welded wire reinforcement.
After a design analysis has been made, it is necessaryto select sheets of welded wire reinforcement to furnishthe required steel areas. There are several conditions thatmay occur. If a uniform distribution of forces has beenassumed a style of reinforcement with constant size andspacing of wires will be suitable. If the maximum com-puted steel area is less than the minimum required bycode, the latter would be employed.
Sheet size is another matter that must be given attention.Although widths up to 13’0”” can be manufactured, theyusually cannot be transported without special permits.For truck shipments, 8’6”” is the limit. As far as length isconcerned, sheets up to 30’ or 40’ can be obtained.
In splicing WWR, a splice of 1.51d (or min. of 2”) mea-sured on the wires parallel to the splice is sufficient,when: As provided
As required≥ 2 (Section 12.19.2)
TABLE 1
Minimum Areas of WWR Reinforcement inAccordance with the ACI Building Code
The ACI Building Code specifies one wire space plus 2”(two-wire splice) when the calculated stress exceedsone-half of the yield strength. In tilt-up panels, laps aregenerally vertical; that is the horizontal wires are spliced.When the panel width is small, or if there are several pick-up points across the panel, stresses in the transversewires frequently will not be large and the 2” minimumsplice discussed above is adequate. However, if veryhigh stresses exist, then the two-wire overlap would berequired.
For panels too wide for a single piece of welded wire rein-forcement, the total width of WWR required is obtainedby subtracting edge clearances from the panel dimen-sion and adding the required splice, then dividing by 8’ or8’6” (max. shipping width allowed without permit), andthe remaining width of sheets may be cut in the field fromstandard widths or made to order. Sheet length is simplythe panel length less end clearances. It may be neces-sary to add or subtract to get a length which is an evenmultiple of the transverse-wire spacing.
With the welded wire reinforcement on chairs, the 3 inch exteriorfacing concrete was cast and struck off with a special template.
Use 9-1/4” x 40’-0””W// 6x6-W13.9 x W5.660 KSI EACH FACE ORW/ 6x6-WII.1 x W4.575 KSI EACH FACE
Consulting engineers should be contacted for specifictilt-up project designs. Most can provide manual analy-ses on a given wall project. Many can provide comput-er analyses similar to the one included in this Tech Factreport.
For guidance on panel inserts along with tilt-up panelsafety contact the Tilt-Up Concrete Association, P.O.Box 204, Mt. Vernon, IA 52314 and the AmericanConcrete Institute, 38800 Country Club Drive,Farmington Hills, MI 48331, (ask for Committee Report,ACI 551).
Example of the computer developed analysis was providedby Baumann Engineering, 567 San Nicholas Dr., NewportBeach, CA 92660.
Credits and acknowledgements for assistance in editing thisdocument are:
Edward Sauter, Executive Director, Tilt-Up Association,Mt. Vernon, IABill Brewer, Brewer Associates, Maumee, OH Don Musser, Consultant, Hendersonville, NCRobert C. Richardson, Consultant, Sun Lakes, AZ
We are very grateful to the Haskill Company, JamesMcFarlane, Jacksonville, FL, and the Ohio Ready MixedConcrete Association for the use of their construction pho-tos of a facility in Troy, OH for Worldwide LogisticsOperations, United Retail Group, a NJ apparel retailer.
This report is furnished as a guide to industry practice. The WireReinforcement Institute (WRI) makes no warranty of any kindregarding the use of this report for other than informational pur-poses. This report is intended for the use of professionals com-petent to evaluate the significance and limitations of its contentsand who will accept responsibility for the application of the mate-rial it contains. WRI provides the foregoing material as a matterof information and, therefore, disclaims any and all responsibilityfor application of the stated principles or the accuracy of thesources other than material developed by the Institute.
What an Engineer Says About WWR . . .. . . in my opinion there is no better way to reinforcetilt-up walls than High Strength Welded WireReinforcement each face. Also, I feel that the step-through patterns and economy edge laps furtherincrease the competitive advantage of High StrengthWelded Wire Reinforcement.
Because of its inherent 2-way spanning capabili-ties, we see a superior performance during lifting asanother distinct advantage.
Recently, more low-rise office buildings aredesigned with up to 5-story high concrete tilt-up wallsat the exterior. The 2way action of the High StrengthWelded Wire Reinforcement around the window open-ings is very valuable in carrying both gravity and windforces . . .
Cast-in-place pan joist slabs can provide economicalconcrete roof and floor construction. They are castabove reusable metal pans, foam panels, fiberglass orplastic pans, concrete or clay tiles, or other forms. Thereusable pans are most frequently used. The ribs mayrun in one or two directions. This slab construction isgenerally known as "one-way pan joists" or "two-waypan joists".
Supporting members may be walls, beams, and girdersof concrete with the reinforcement continuous over thesupport. In some cases, particularly with two-way sys-tems, supporting beams are made the same depth asthe slab, forming a structure that is essentially a ribbedflat slab, often called a "waffle slab" or "dome slab'.Usually at the columns there is a square or rectangulararea where the slab is solid, comparable to the droppanel in normal flat-slab construction.
Minimum WWR RequirementsWelded wire has long been used for reinforcing in thetop slabs of both one-way and two-way pan joist slabs,minimum steel (that required for temperature andshrinkage crack control) is necessary, as indicated inthe 1989 ACI Building Code.
ACI 318, Section 7.12 specifies a shrinkage and tem-perature reinforcement ratio, As/Ag, of 0.0018 for 60 ksiyield strength WWR and a reduced shrinkage and tem-perature reinforcement ratio where WWR with yieldstrength exceeding 60 ksi (measured at a strain of0.35%) is used, but not to be less than 0.0014. It alsospecifies that reinforcing members shall not be spacedfarther apart than 5 times the slab thickness nor 18inches. Table 1 combines these requirements.
The maximum spacings and minimum steel areas (seeACI 318, Section 7.12) in Table I are for wires in bothdirections.
Sheets of WWR may be curved from a point near thetop of the slab over the support to a point near the bot-tom of the slab at midspan (see ACI 318, Section 7.5.3)or remain in a flat position (1/2 distance from the top ofthe slab but not lower than the center of the slab).
TABLE 1
See Table 2 for suitable WWR styles for one-way andtwo-way pan joist slabs.
It is advantageous to utilize the benefit that highstrength wire for WWR offers. Cold working increasesthe yield strength of low carbon steel rod. AC! 318allows the use of high strength reinforcement whentests show that the specified yield strength (usually 70,72.5, 75, & 80 ksi) is developed at 0.35% strain.(Testing of wire to ASTM standards measures yieldstrength at 0.50% strain.)
SlabThickness, h
(in.)
Maximum1Steel Area
(sq. in. per ft.)
Minimum1Steel Area
(sq. in. per ft.)
11/2 7.5 0.032
2 10 0.043
21/2 12.5 0.054
3 15 0.065
31/2 17.5 0.076
4 18 0.086
41/2 18 0.097
5 18 0.108
51/2 18 0.119
1Minimum steel area is based on a shrinkage and temperature reinforcementratio of 0.0018 for WWR with 60 ksi yield strength. When WV/F with greaterthan 60 ksi is used, a reduced shrinkage and temperature ratio is used inaccordance with AC1 318, Section 7.12.
WWRshearreinf. Continuous
supportsfor WWR
WWR sheets placedin center of slab
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 2 • TF 205-R-03
Table 2 shows two columns of suitable styles that canbe compared by engineers and contractors to measurethe cost savings using high strength wire. Many timesthe cost benefit can be 20 - 25% less cost for the highstrength reinforcing. WWR styles in Table 2 show wireareas that are best suited for current manufacturing effi-ciencies and exceed minimum area requirements inTable 1. Capabilities of producing the various levels ofhigh strength wire as well as the different wire sizesvary between manufacturers. Check with your nearestWRI manufacturer for advise on the most economicalstyles available.
TABLE 2One-Way and Two-Way Pan Joist Slab Reinforcing
Structural Welded Wire ReinforcementIf flexural computations indicate requirements greaterthan the minimum areas set out in Table 1 then Table 2will be inadequate. The engineer will need to specify therequired WWR styles with wire sizes designed to resistflexural stresses and thermal and shrinkage stresses.See Figure 1 below for an example of structural WWR.
Similarly, for two-way pan joist slabs, styles giving min-imum areas to resist thermal and shrinkage stresses inaccordance with ACI 318, Section 7.12 can be selectedfrom Table 2.
Welded wire reinforcement can also be used to advan-tage as negative steel over the supporting beam or solidportion of the slab. Here the wires placed parallel to thebeam provide minimum slab steel (or that indicated byflexure for the span between ribs) and the wires per-pendicular to the beam provide the negative slab steel,as indicated by design calculations. Figure 1 shows alayout for such a situation. Note that styles and sizes ofwire indicated fit a particular load situation and may notbe suited for other applications. Consult your structuralengineer on design for specific project applications.
FIGURE 1I = Sheet of WWR 3x6 - W9 x W4.5H = Sheet of WWR 6x6 - W4.5 x W4.5
SlabThickness
(in.) 60 ksi
60 ksi
80 ksi2
11/2 12x12 - W3.2 x W3.2 12x12 - W2.5 x W2.5
2 12x12 - W4.3 x W4.3 12x12 - W3.4 x W3.4
21/2 12x12 - W5.4 x W5.4 12x12 - W4.2 x W4.2
3 12x12 - W6.5 x W6.5 12x12 - W5.0 x W5.0
31/2 12x12 - W7.6 x W7.6 12x12 - W5.9 x W5.9
4 12x12 - W8.6 x W8.6 12x12 - W6.7 x W6.7
41/2 12x12 - W9.7 x W9.7 12x12 - W7.6 x W7.6
5 12x12 - W10.8 x W10.8 12x12 - W8.4 x W8.4
51/2 12x12 - W11.9 x W11.9 12x12 - W9.3 x W9.3
1 Minimum steel areas are controlled by the minimum ratio 0.0014 (see ACI318, Section 7.12).
This publication is furnished as a guide for the selection of welded wire fabricreinforcement with the understanding that while every effort has been made toinsure accuracy, neither the Wire Reinforcement Institute, Inc., nor its membercompanies make any warranty of any kind respecting the use of the publica-tion for other than informational purposes.
* Note - The prefix W is for plain wire but may also be deformed wire with aprefix D when areas exceed 0.04 sq. in.
Industry Method of Designating Style:Example - 6 x 12 - W12 x W5*
Longitudinalwire spacing Longitudinal
wire size Transverse
wire spacing Transversewire size
Suitable WWR Styles To Provide MinimumSteel for One-Way and Two-Way Pan Joist*
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
TF 206-R-03
When A Job Calls Out Metric, Soft Convert WWRWhat do you do when a job specification calls outmetric styles of reinforcement but welded wirereinforcement (WWR) is available only in U.S.customary (inch-pound) styles?
SOFT METRICATEOne of the legacies of the decades-old and as-yetunrealized attempt to convert the U.S. measuring sys-tem to the metric system is that a small percentage ofjobs today specify metric styles of reinforcement. Yet,even though few if any WWR producers possess thenecessary machinery to meet the metric specification,this does not preclude taking advantage of the per-formance and cost benefits of using WWR.
With its greater strength, generally higher ductility, andsignificantly lower placing costs, WWR is a highlypractical and cost-efficient alternative to traditionalrebar concrete reinforcement.
WWR may be used in virtually any structural applica-tion—buildings, bridges, highways, tunnels, pipelinesand precast component systems, for instance—thattypically would rely on rebar to fortify concrete. In fact,
both ACI and AASHTO have considered WWRcomparable to rebar for many years, and testingrequirements—i.e., tensile, yield strength at variousstrain rates, and bend testing—are similar for bothproducts. WWR, moreover, adheres to additionalrequired tests, such as reduction of area (ROA) andwrap and weld shear testing (with 50% of the sampleshaving the weld in the center of the gage length).
COMMON STYLES OF METRIC WELDED WIRE REINFORCEMENT (WWR) WITH EQUIVALENT US CUSTOMARY UNITS3
1 Group A - Compares areas of WWR at fy = 60,000 psi with other reinforcing at fy = 60,000 psiGroup B - Compares areas of WWR at fy = 70,000 psi with other reinforcing at fy = 60,000 psiGroup C - Compares areas of WWR at fy = 72,500 psi with other reinforcing at fy = 60,000 psiGroup D - Compares areas of WWR at fy = 75,000 psi with other reinforcing at fy = 60,000 psiGroup E - Compares areas of WWR at fy = 80,000 psi with other reinforcing at fy = 60,000 psi
2Wires may also be deformed, use prefix MD or D, except where only MW or W is required by building codes (usually less than a MW26 or W4). Also wire sizes can be specified in 1mm2 (metric) or .001 in.2 (US Customary) increments.
3For other available styles or wire sizes, consult other WRI publications or discuss with WWR manufacturers.4Styles may be obtained in roll form. Note: It is recommended that rolls be straightened and cut to size before placement.
Structural WWR sheets in the foreground; base rod material in the background.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
When specifying WWR in metric styles, convert theU.S. Equivalent Customary (in-pound) styles to Metricstyles and round to whole numbers. The balance of thisTech Fact discusses this soft conversion techniqueand provides examples.
STRUCTURAL WELDED WIRE REINFORCEMENT METRICSTYLES (styles with wire areas from MW or MD26 to MW or MD290) will have both wire spacings and wire areas rounded towhole numbers.
BUILDING FABRIC STYLES / METRIC STYLES(styles with wire areas less than MW or MD26),as with the structural WWR styles, wire spacings andwire areas will be rounded to whole numbers.Pipe fabric styles and wire sizes will be published inanother tech fact.
EXAMPLES*1. A typical metric structural WWR style is:
305 x 305 - MD 71 x MD 71
The equivalent inch-pound structural WWR style is:12 x 12 - D11 x D11
2. A typical metric building fabric style is:152 x 152 - MW 19 x MW 19
The equivalent inch-pound building fabric style is:6 x 6 - W2.9 x W2.9
Note: Wire spacings are in millimeters (mm) and wireareas are in square millimeters (mm2). The MD (metric)or D (inch-pound) prefixes designate deformed wire.The MW (metric) or W (inch-pound) prefixes designateplain wire.
To determine sheet sizing, soft convert width of sheetsfrom inches to millimeters and lengths of sheets fromfeet to meters. An example is: 2438 mm x 6.1 m equals96” x 20’ Building fabric rolls are figured similarly, forexample: 1524 mm x 45.7 m equals 60” x 150’
For mass (weight) calculations use: wire area in mm2 x 0.00784 = mass (kg/meter). For the inch-pound unitequivalent use: wire area in in2 x 3.4 = weight(Ibs./foot).
*Conversion faclors: 25.4 mm = 1 inch, 645 mm2 = 1inch2, 304.8 mm = I foot. A reminder, the inch-poundwire areas in the examples are in2 multiplied by 100.
LOOKING TO THE FUTUREIt is important for design professionals, contractors, dis-tributors and fabricators to know they can specify andorder the exact area of steel required for their individualprojects. Therefore, for some time in the future, mostwire sizes will be available in 1 mm2 (.001 in2) increments.
A table of 24 metric wire sizes and properties along withthe equivalent inch-pound units and also a conversiontable on WWR styles are reproduced in this tech factsheet. The intent of the tables are to have design pro-fessionals begin specifying welded wire styles in 5 and10 square millimeter increments above an MW or MD26. Below that size WRI will list the typical standards(MW 9, MW 13, MW 19 and MW 26), as well as the5mm2 increments in between (MW 10, MW 15, MW 20).
In addition to this information WRI has soft convertedtables in the current “Manual of Standard Practice forStructural WWR” (WWF 500), commonly referred to asthe MSP.
ADDITIONAL DATA INCLUDED IN THE MSP Along with discussion on nomenclature, manufacturingand availability, specifications, handling and placing,there are these subjects as well:Design Aids—Tables on cross sectional areas of welded wirefor (51 mm to 457 mm) 2 “ to 18 “ wire spacings are included.
Development and Splice Lengths—Tables for wire areas fromMW or MD 26 to MW or MD 290 (W or D 4 to W or D 45).Mass (Weight) Calculations—There are tables to determinemetric units (kg per meter) or inch-pound units (Ibs. per foot)for efficient calculations.
*Metric wire sizes canbe specified in 1mm2
increments.
**U.S. customary sizescan be specified in.001 in2 increments.
Note ✩ – For otheravailable wire sizes,consult other WRIPublications or discusswith WWF manufactur-ers.
Note ★ – Wires maybe deformed, use pre-fix MD or D, exceptwhere only MW or Wis required by buildingcodes (usually lessthan MW26 or W4).
WWR rolls and bundles of structural sheets ready for shipment.
Page 2 • TF 206-R-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
TF 207-R-03
A Consolidated GuideACI 318 Provisions and ASTM Referencesfor Specifying WWRFor architects, engineers, contractors and others whointend to use or are considering the use of high-performance, lightweight, cost-efficient welded wirereinforcement (WWR), this publication contains keycode provisions concerning wire and WWR forreinforced concrete design.
The reference can be used as a guide for designexpressions, approved ASTM material referencesand commentary to assist in the design of WWR inconcrete structures. The various chapters and sectionsthat reference wire and WWR are taken from thecurrent ACI 318 Building Code for Structural Concreteand Commentary*. Refer to the ACI Code for completedocumentation and commentary on specific sections.Permission to reprint these data has been grantedby the American Concrete Institute.
KEY CODE UPDATES ORCHANGES MADE IN RECENT YEARS:
1. Supported or suspended structural slabs withminimum steel reinforcement can be found inChapter 7. An expression exists to substitute highstrength WWR over 60 ksi yield strength - SeeChapters 3 and 7. All ASTM Standard referencesnoted throughout the Code, covering structuralwire and WWR include a supplement allowing up to80 ksi reinforcement. Note the ACI 318 code atpresent does not cover structural slabs on ground.Refer to other WRI references for the designprocedures of structural slabs on ground.
2. The latest Code provisions for confinement andshear reinforcement can be found in Chapters 11. TheCode now recognizes shear reinforcement up to80,000 psi yield strength for deformed WWR. It hasrecognized up to 80,000 psi yield strength in flexurefor many years and is stated in Chapter 9.
3. Wall reinforcement provisions and minimum require-ments can be found in Chapters 14 and 21. Chapter 14refers to steel ratio requirements for both rebar and
WWR. Both reinforcing materials can be specified. SeeSpecial Provisions for Seismic Design in Chapter 21.Higher ratios of reinforcement are required in Chapter21. Paragraph 21.2.1.5 states that other structuralmaterials or structural systems not previously recog-nized are approved if research data shows evidence ofmeeting strength and toughness equal to or exceedingChapter 21 requirements.
4. Epoxy-coated welded wire reinforcement is nowrecognized by the Code in Chapters 3 and 12.Statements have been added to include the referenceof ASTM A 884 for the coated reinforcement. Alsotesting is referenced in Chapter 12 which shows thatno additional splice lengths are necessary over un-coated WWR. The welded intersections of WWRprovide sufficient bond strength to resist shearstresses. Research work by the University of Texason the subject is referenced in the Code. It can befound in the commentary of Chapter 12, R12.7 - Alsosee the footnote reference 12.11 in the back of the Code.
5. In future Codes the largest cold worked wire sizewill be increased to a W45 or D45 (3/4” diameter)wire sizes. The size wire is now available by some WRIproducer plants.
6. Recent research work on high strength wire withhigh ductility is now noted in Chapter 11, R11.5.2.The research papers are listed near the back of theCode as 11.15, 11.16 and 11.17. As a reminder, thesereferences can be considered for projects that fall inthe category of special provisions as described in #3above.
*The provisions in this Tech Fact can be found in ACI 318-02.This Tech Fact may be inserted in the WRI Structural DetailingManual section and will be updated as future Codes are published.
The last page has a listing of applicable ASTM Standards for wireand WWR.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 2 • TF 207-R-03
Section 1PROVISIONS OF ACI 318* BUILDING CODE REQUIRE-MENTS FOR REINFORCED CONCRETE WHICH APPLYTO WELDED WIRE REINFORCEMENT FABRIC
Welded plain wire reinforcement fabric (WWR) andwelded deformed wire reinforcement fabric are bothdefined in ACI 318, Section 2.1, as DeformedReinforcement. Since welded wire reinforcement issupplied in sheets or mats instead of individual bars,additional descriptive provisions are necessary and arefound in Section 2. See Appendix C, for wire diame-ters, wire areas and areas per unit of width. Other WireReinforcement Institute’s publications are available forareas of reinforcement with various strengths, as wellas development and splice lengths for different styles.
For the convenience of architects and engineers,some provisions related to WWR are reprinted fromACI 318 and will be referred to by code chapters andpertinent sections in this manual. Some metric dataand formulas are presented in the Wire ReinforcementInstitutes Manual of Standard Practice, StructuralWelded Wire Reinforcement, copyright, 1999.
CHAPTERS OF ACI 318-95 FORWELDED WIRE REINFORCEMENT:CHAPTER 3 - MATERIALS3.5 - Metal reinforcement
3.5.3 - Deformed reinforcement
3.5.3.4 - Deformed wire for concrete reinforcementshall conform to “Specifications for Steel Wire,Deformed, for Concrete Reinforcement” (ASTM A 496),except that wire shall not be smaller than size D4 andfor wire with a specified yield strength fy exceeding60,000 psi, fy shall be the stress corresponding to astrain of 0.35 percent if the yield strength specified inthe design exceeds 60,000 psi.3.5.3.5 - Welded plain wire reinforcement fabric forconcrete shall conform to “Specification for SteelWelded Wire Reinforcement Fabric, Plain, forConcrete” (ASTM A 185), except that for wire with aspecified yield strength fy exceeding 60,000 psi, fy shallbe the stress corresponding to a strain of 0.35 percentif the yield strength specified in the design exceeds60,000 psi. Welded intersections shall not be spacedfarther apart than 12 in. in direction of calculated stress,except for wire fabric used as stirrups in accordancewith 12.13.2.
3.5.3.6 - Welded deformed wire reinforcement fabric forconcrete shall conform to “Specification for SteelWelded Wire Fabric, Deformed, for Concrete Rein-
forcement” (ASTM A 497), except that for wire with aspecified yield strength fy exceeding 60,000 psi, fy shallbe stress corresponding to a strain of 0.35 percent ifthe yield strength specified in the design exceeds60,000 psi. Welded intersections shall not be spacedfather apart than 16 in. in direction of calculated stress,except for wire fabric used as stirrups in accordancewith 12.13.2.
3.5.3.8 - Epoxy - Coated wires and WWR shall comply with ASTM A 884.
3.8 - Standards cited in this code
3.8.1 - Standards of the American Society for Testingand Materials referred to in this code are listedbelow, and are declared part of this code:
A 82 Standard Specification for Steel Wire, Plain, forConcrete Reinforcement
A 185 Standard Specification for Steel Welded Wire Reinforcement *Fabric, Plain, for Concrete
A 496 Standard Specification for Steel Wire, Deformed, for Concrete Reinforcement
A 497 Standard Specification for Steel Welded Wire Reinforcement *Fabric, Deformed, for Concrete
A 884 Standard Specification for Epoxy - Coated SteelWire and Welded Wire Fabric for Reinforcement
CHAPTER 7 - DETAILS OF REINFORCEMENT7.2 - Minimum bend diameters
7.2.3 - Inside diameter of bends in welded wire fabric(plain or deformed) for stirrups and ties shall not be lessthan 4db for deformed wire larger than D6 and 2db forall other wires. Bends with inside diameter of less than 8db
shall not be less than 4db from nearest welded intersection.
7.5.3 - Welded wire fabric (with wire size not greaterthan W5 or D5) used in slabs not exceeding 10 ft. inspan may be curved from a point near the top of slabover the support to a point near the bottom of slab atmidspan, provided such reinforcement is either contin-uous over, or securely anchored at support.
7.6 - Spacing limits for reinforcement
7.6.5 - In walls and slabs other than concrete joist con-struction, primary flexural reinforcement shall not bespaced farther apart than 3 times the wall or slab thick-ness, nor 18 in.
7.10.5 - TiesTie reinforcement for compression members shall con-form to the following:
7.10.5.1 - All nonprestressed bars shall be enclosed bylateral ties, at least #3 in size for longitudinal bars #10or smaller, and at least #4 in size for #11, $14, #18, and
* Expressions or factors being considered for change in future codes.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 3 • TF 207-R-03
bundled longitudinal bars. Deformed wire or weldedwire fabric of equivalent areas is allowed.
7.10.5.2 - Vertical spacing of ties shall not exceed 16longitudinal bar diameters, 48 tie bar or wire diameters,or least dimension of the compression member.
7.11 - Lateral reinforcement for flexural members
7.11.3 - Closed ties or stirrups shall be formed in onepiece by overlapping standard stirrup or tie and hooksaround a longitudinal bar, or formed in one or twopieces lap spliced with a Class B splice (lap of 1.3 d),or anchored in accordance with 12.13.
7.12 - Shrinkage and temperature reinforcement
7.12.1 - Reinforcement for shrinkage and temperaturestresses normal to flexural reinforcement shall beprovided in structural slabs where the flexural rein-forcement extends in one direction only.
7.12.2.1 - Area of shrinkage and temperature reinforce-ment shall provide at least the following ratios of rein-forcement area to gross concrete area, but not lessthan 0.0014:
(a) Slabs where Grade 40 or 50 deformed bars areused . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0.0020(b) Slabs where Grade 60 deformed bars or weldedwire fabric (plain or deformed) are used . . .0.0018(c) Slabs where reinforcement with yield stressexceeding 60,000 psi measured at a yield strain of0.35 percent is used . . . . . . . . . . .0.0018 x 60,000
7.12.2.2 - Shrinkage and temperature reinforcementshall not be spaced farther apart than 5 times the slabthickness, nor 18 in.
7.12.2.3 - At all sections where required, reinforcementfor shrinkage and temperature stresses shall developthe specified yield strength fy in tension in accordancewith Chapter 12.Note - For additional details of WWR refer to ACI 318-95, Chapter 7.
CHAPTER 9- STRENGTH AND SERVICEABILITYREQUIREMENTS9.4 - Design strength for reinforcementDesigns shall not be based on a yield strength ofreinforcement fy in excess of 80,000 psi, except forprestressing tendons.
CHAPTER 11 - SHEAR AND TORSION11.5 - Shear strength provided by shear reinforcement
11.5.1 - Types of shear reinforcement
11.5.1.1 - Shear reinforcement may consist of:(a) Stirrups perpendicular to axis of member.(b) Welded wire fabric with wires located
perpendicular to axis of member.
11.5.1.2 - For nonprestressed members, shearreinforcement may also consist of:
(a) Stirrups making an angle of 45 degrees or more with longitudinal tension reinforcement.
(b) Longitudinal reinforcement with bent portion making an angle of 30 degrees or more with the longitudinal tension reinforcement.
(c) Combinations of stirrups and bent longitudinal reinforcement.
(d) Spirals.
11.5.2 - Design yield strength of shear reinforcementshall not exceed 60,000 psi, except that the designyield strength of welded deformed wire fabric shall notexceed 80,000 psi.
11.5.3 - Stirrups and other bars or wires used as shearreinforcement shall extend to a distance d fromextreme compression fiber and shall be anchored atboth ends according to 12.13 to develop the designyield strength of reinforcement.
11.5.4 - Spacing limits for shear reinforcement
11.5.4.1 - Spacing of shear reinforcement placed per-pendicular to axis of member shall not exceed d/2 innonprestressed members and 3/4h in prestressedmembers, nor 24 in.
11.6 - Combined shear and torsion strength fornon-prestressed members with rectangular or flangedsections
11.6.7 - Torsion reinforcement requirements
11.6.7.1 - Torsion reinforcement, where required, shallbe provided in addition to reinforcement required toresist shear, flexure, and axial forces.
11.6.7.2 - Reinforcement required for torsion shall becombined with that required for other forces, providedthe area furnished is the sum of individually requiredareas and the most restrictive requirements for spacingand placement are met.
11.6.7.3 - Torsion reinforcement shall consist of closedstirrups, closed ties, or spirals, combined with longitu-dinal bars.
11.6.7.4 - Design yield strength of torsion reinforcementshall not exceed 60,000 psi.
11.6.7.5 - Stirrups and other bars and wires used astorsion reinforcement shall extend to a distance d fromextreme compression fiber and shall be anchoredaccording to 12.13 to develop the design yield strengthof reinforcement.
11.6.7.6 - Torsion reinforcement shall be provided atleast a distance (bt + d) beyond the point theoreticallyrequired.
11.6.8 - Spacing limits for torsion reinforcement
fy
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 4 • TF 207-R-03
11.6.8.1 - Spacing of closed stirrups shall notexceed the smaller of (x1 + y1)/4, or 12 in.
11.6.8.2 - Spacing of longitudinal bars, not lessthan #3, distributed around the perimeter of theclosed stirrups, shall not exceed 12 in. At leastone longitudinal bar shall be placed in each cornerof the closed stirrups.#3, distributed around theperimeter of the closed stirrups, shall not exceed12 in. At least one longitudinal bar shall be placedin each corner of the closed stirrups.
CHAPTER 12 - DEVELOPMENT AND SPLICES OFREINFORCEMENT
12.1 - Development of reinforcement - General
12.1.1 - Calculated tension or compression inreinforcement at each section of reinforcedconcrete members shall be developed on eachside of that section by embedment length, hook ormechanical device or a combination thereof. Hooksmay be used in developing bars in tension only.
12.2 - Development of deformed bars anddeformed wire in tension
12.2.1 - Development length d, in terms of diam-eter db for deformed bars and deformed wires intension shall be determined from either 12.2.2 or12.2.3, but d shall not be less than 12 in.
12.2.2 - For deformed bars or deformed wire,d/db shall be as follows:
12.2.3 - For deformed bars or deformed wire,d/db shall be:
in which the term (c + Ktr)/db shall not be takengreater than 2.5.
12.2.4 - The factors for use in the expressions fordevelopment of deformed bars and deformedwires in tension in Chapter 12 are as follows:α = reinforcement location factorHorizontal reinforcement so placed that more than
12 in. of fresh concrete is cast in the memberbelow the development length or splice . . . . .1.3Other reinforcement . . . . . . . . . . . . . . . . . . . .1.0β = coating factorEpoxy-coated bars or wires with cover less than3db1or clear spacing less than 6db . . . . . . . . .1.5All other epoxy-coated bars or wires . . . . . . .1.2Uncoated reinforcement . . . . . . . . . . . . . . . . .1.0However, the product of need not be takengreater than 1.7.
γ = reinforcement size factor
No. 6 and small bars and deformed wires . . .0.8No. 7 and larger bars . . . . . . . . . . . . . . . . . . .1.0
λ = lightweight aggregate concrete factorWhen lightweight aggregate concrete is used 1.3
However, when fct is specified, shall be permittedto be taken as 6.7 but not less than . . . . . . . .1.0When normal weight concrete is used . . . . . .1.0
c = spacing or cover dimension, inc.Use the smaller of either the distance from thecenter of the bar or wire to the nearest concretesurface or one-half the center-to-center spacing ofthe bars or wires being developed.
It shall be permitted to use Ktr=0 as a designsimplification even if transverse reinforcement ispresent.
12.3 - Development of deformed bars in compression
12.3.1 - Development length d1 in inches, fordeformed bars in compression shall be computedas the product of the basic development length
db of 12.3.2 and applicable modification factorsof 12.3.3, but d shall be not less than 8 in.
but not less than . . . . . . . . . . . . . . .0.0003dbfy***
12.3.3 - Basic development length db shall bepermitted to be multiplied by applicable factors for:
12.3.3.1 - Excess reinforcementReinforcement in excess of that required byanalysis . . . . . . . . . . . .(As required)/As provided)
12.7 - Development of welded deformed wirefabric in tension
12.7.1 - Development length d, in inches, ofwelded deformed wire fabric measured from thepoint of critical section to the end of wire shall be
Clear spacing of bars beingdeveloped or spliced not less thandb, clear cover not less than db, andstirrups or ties throughout d notless than the code minimum
orClear spacing of bars beingdeveloped or spliced not less than2db and clear cover not less than db
No. 6 andsmaller bars anddeformed wires
No. 7 and largerbars
Other cases
* Expressions or factors being considered for change in future codes.**The constant carries the unit of in.2/lb.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 5 • TF 207-R-03
computed as the product of the developmentlength d, from 12.2.2 or 12.2.3 times a wire fab-ric factor from 12.7.2 or 12.7.3. It shall be permit-ted to reduce the development length in accor-dance with 12.2.5 when applicable, but d shallnot be less than 8 in. except in computation of lapsplices by 12.18. When using the wire fabric fac-tor from 12.7.2, it shall be permitted to use anepoxy-coated factor β of 1.0 for epoxy-coatedwelded wire fabric in 12.2.2 and 12.2.3.
12.7.2 - For welded deformed wire fabric with atleast one cross wire within the developmentlength and not less than 2 in. from the point of thecritical section, the wire fabric factor shall be thegreater of:
or
but need not be taken greater than 1.
12.7.3 - For welded deformed wire fabric with nocross wires within the development length or witha single cross wire less than 2 in. from the point ofthe critical section, the wire fabric factor shall betaken as 1, and the development length shall bedetermined as for deformed wire.
12.7.4 - When any plain wires are present in thedeformed wire fabric in the direction of the devel-opment length, the fabric shall be developed inaccordance with 12.8.
12.8 - Development of welded plain wire fabric intension. Yield strength of welded plain wire fabricshall be considered developed by embedment oftwo cross wires with the closer cross wire not lessthan 2 in. from the point of the critical section.However, the development length d, in inches,measured from the point of the critical section tothe outermost cross wire shall not be less than:
except that when reinforcement provided is inexcess of that required, this length may bereduced in accordance with 12.2.5. d shall notbe less than 6 in. except in computation of lapsplices by 12.19.
12.13 - Development of web reinforcement
12.13.2 - Ends of single leg, simple U-, or multipleU-stirrups shall be anchored by one of the follow-ing means:
12.13.2.1 - For #5 bar and D31 wire, and smaller,and for #6, #7, and #8 bars with fy of 40,000 psi orless, a standard hook around longitudinalreinforcement.
12.13.2.2 - For #6, #7, and #8 stirrups with fygreater than 40,000 psi, a standard stirrup hookaround a longitudinal bar plus an embedmentbetween midheight of the member and theoutside end of the hook equal to or greater than0.014dbfy/
12.13.2.3 - For each leg of welded plain wirefabric forming simple U-stirrups, either:(a) Two longitudinal wires spaced at a 2 in.
spacing along the member at the top of the U.
(b) One longitudinal wire located not more thand/4 from the compression face and a secondwire closer to the compression face and spacednot less than 2 in. from the first wire. The sec-ond wire may be located on the stirrup legbeyond a bend, or on a bend with an insidediameter of bend not less than 8db.
12.13.2.4 - For each end of a single leg stirrup ofwelded plain or deformed wire fabric, two longitu-dinal wires at a minimum spacing of 2 in. and withthe inner wire at least the greater of d/4 or 2 in.from middepth of member d/2. Outer longitudinalwire at tension face shall not be farther from theface than the portion of primary flexural reinforce-ment closest to the face.
12.15 - Splices of deformed bars and deformedwire in tension
12.15.1 - Minimum length of lap for tension lapsplices shall be as required for Class A or B splice,but not less than 12 in., where:
Class A splice . . . . . . . . . . . . . . . .1.0 d.Class B splice . . . . . . . . . . . . . . . .1.3 d.
where d is the tensile development length for thespecified yield strength fy in accordance with 12.2without the modification factor of 12.2.5.
12.15.2 - Lap splices of deformed bars anddeformed wire in tension shall be Class B splicesexcept that Class A splices are allowed when: (a)the area of reinforcement provided is at leasttwice that required by analysis over the entirelength of the splice, and (b) one-half or less of thetotal reinforcement is spliced within the requiredlap length.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 6 • TF 207-R-03
12.18 - Splices of welded deformed wire in tension
12.18.1 - Minimum length of lap for lap splices of weld-ed deformed wire fabric measured between the ends ofeach fabric sheet shall be not less than 1.3 d nor 8 in.,and the overlap measured between outermost crosswires of each fabric sheet shall not be less than 2 in.
d shall be the development length for the specifiedyield strength fy in accordance with 12.7.
12.18.2 - Lap splices of welded deformed wire fabric,with no cross wires within the lap splice length, shall bedetermined as for deformed wire.
12.19 - Splices of welded plain wire fabric in tension
Minimum length of lap for lap splices of welded plainwire fabric shall be in accordance with the following.
12.19.1 - When area of reinforcement provided is lessthan twice that required by analysis at splice location,length of overlap measured between outermost crosswires of each fabric sheet shall be not less than onespacing of cross wires plus 2 in., nor less than 1.5 d,nor 6 in. d shall be the development length for thespecified yield strength fy in accordance with 12.8.
12.19.2 - When area of reinforcement provided is atleast twice that required by analysis at splice location,length of overlap measured between outermost crosswires of each fabric sheet shall be not less than 1.5 d,nor 2 in. d shall be the development length for thespecified yield strength fy in accordance with 12.8.
CHAPTER 14 - WALLS
14.2 - General
14.2.7 - Quantity of reinforcement and limits of thicknessrequired by 14.3 and 14.5 are waived where structuralanalysis shows adequate strength and stability.
14.3 - Minimum reinforcement
14.3.1 - Minimum vertical and horizontal reinforcementshall be in accordance with 14.3.2 and 14.3.3 unless a greater amount is required for shear by11.10.8 and 11.10.9.
14.3.2 - Minimum ratio of vertical reinforcement area togross concrete area shall be:
(a) 0.0012 for deformed bars not larger than #5 with a specified yield strength not less than 60,000 psi, or
(b) 0.0015 for other deformed bars, or
(c) 0.0012 for welded wire fabric (plain or deformed) not larger than W31 or D31.
14.3.3 - Minimum ratio of horizontal reinforcement areato gross concrete area shall be:
*(a) 0.0020 for deformed bars not larger than #5 with a specified yield strength not less than 60,000 psi, or
(b) 0.0025 for other deformed bars, or
(c) 0.0020 for welded wire fabric (plain or deformed) not larger than W31 or D31.
14.3.4 - Walls more than 10 in. thick, except basement walls,shall have reinforcement for each direction placed in two lay-ers parallel with faces of wall in accordance with the following:
(a) One layer consisting of not less than 1/2 and notmore than 2/3 of total reinforcement required for eachdirection shall be placed not less than 2 in. nor morethan 1/3 the thickness of wall from exterior surface.
(b) The other layer, consisting of the balance ofrequired reinforcement in that direction, shall be placednot less than 3/4 in. nor more than 1/3 the thickness ofwall from interior surface.
14.3.5 - Vertical and horizontal reinforcement shall notbe spaced further apart than three times the wallthickness, nor 18 in.
14.3.6 - Vertical reinforcement need not be enclosedby lateral ties if vertical reinforcement area is notgreater than 0.01 times gross concrete area, or wherevertical reinforcement is not required as compressionreinforcement.
14.3.7 - In addition to the minimum reinforcementrequired by 14.3.1, not less than two #5 bars shall beprovided around all window and door openings. Suchbars shall be extended to develop the bar beyond thecorners of the openings but not less than 24 in.
CHAPTER 21 - SPECIAL PROVISIONS FORSEISMIC DESIGN
21.2 - General requirements
21.2.1 - Scope
21.2.1.1 - Chapter 21 contains special requirements fordesign and construction of reinforced concrete membersof a structure for which the design forces, related to earth-quake motions, have been determined on the basis ofenergy dissipation in the nonlinear range of response.
21.2.1.2 - The provisions of Chapters 1 through 18shall apply except as modified by the provisions of thischapter.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 7 • TF 207-R-03
21.2.1.3 - In regions of moderate seismic risk, rein-forced concrete frames resisting forces induced byearthquake motions shall be proportioned to satisfyonly 21.8 of Chapter 21 in addition to the requirementsof Chapters 1 though 18.
21.2.1.4 - In regions of high seismic risk, all structuralreinforced concrete members shall satisfy 21.2 through21.7 of Chapter 21 in addition to the requirements ofChapters 1 through 17.
21.2.1.5 - A reinforced concrete structural system notsatisfying the requirements of this chapter is allowed ifit is demonstrated by experimental evidence andanalysis that the proposed system will have strengthand toughness equal to or exceeding those provided bya comparable monolithic reinforced concrete structuresatisfying this chapter.
21.2.6.2 - Welding of stirrups, ties, inserts, or other sim-ilar elements to longitudinal reinforcement required bydesign shall not be permitted.
R21.2.6.2 - Welding or tack-welding or cross rein-forcing bars can lead to local embrittlement of thesteel. If such welding will facilitate fabrication or fieldinstallation, it must be done only on bars addedexpressly for construction.
Provisions for tack-welding of crossing reinforcing bars do not apply to materials that are welded with welding operations under continuous competent control as inthe manufacture of welded wire fabric.
21.3.3 - Transverse reinforcement
21.3.3.1 - Hoops shall be provided in the followingregions of frame members:
(1) Over a length equal to twice the member depthmeasured from the face of the supporting member toward midspan, at both ends of the flexural member.
(2) Over lengths equal to twice the member depth onboth sides of a section where flexural yielding islikely to occur in connection with inelastic lateraldisplacements of the frame.
21.3.3.2 - The first hoop shall be located not more than2 in. from the face of a supporting member. Maximumspacing of the hoops shall not exceed (a) d/4, (b) eighttimes the diameter of the smallest longitudinal bars, (c)24 times the diameter of the hoop bars, and (d) 12 in.
21.3.3.3 - Where hoops are required, longitudinal barson the perimeter shall have lateral support conformingto 7.10.5.3.
21.3.3.4 - Where hoops are not required, stirrups shallbe spaced at no more than d/2 throughout the length ofthe member.
21.3.3.5 - Stirrups or ties required to resist shear shallbe hoops over lengths of members as specified in21.3.3, 21.4.4, and 21.5.2.
21.3.3.6 - Hoops in flexural members are allowed to bemade up two pieces of reinforcement: a U-stirrup hav-ing hooks not less than 135 deg. with six-diameter (butnot less than 3 in.) extension anchored in the confinedcore and a crosstie to make a closed hoop.Consecutive crossties engaging the same longitudinalbar shall have their 90-deg. hooks at opposite sides ofthe flexural member. If the longitudinal reinforcing barssecured by the crossties are confined by a slab only onone side of the flexural frame member, the 90-deg.hooks of the crossties shall all be placed on that side.
21.6 - Structural walls, diaphragms, and trusses
21.6.1 - Scope
21.6.2 - Reinforcement
21.6.2.1 - The reinforcement ratio, rv, for structuralwalls shall not be less than 0.0025 along the longitudi-nal and transverse axes. If the design shear force doesnot exceed Acv , the minimum reinforcement forstructural walls shall be in conformance with 14.3. Theminimum reinforcement ratio for structural diaphragmsshall be in conformance with 7.12. Reinforcementspacing each way in structural walls and diaphragmsshall not exceed 18 in. Reinforcement provided forshear strength shall be continuous and shall be distrib-uted across the shear plane.
21.6.2.2 - At least two curtains of reinforcement shallbe used in a wall if the in-plane factored shear forceassigned to the wall exceeds 2Acv
* Expressions or factors being considered for change in future codes.
**The constant carries the unit of in.2/lb.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 8 • TF 207-R-03
This report is furnished as a guide to industry practice. TheWire Reinforcement Institute (WRI) and its members make nowarranty of any kind regarding the use of this report for otherthan informational purposes. This report is intended for the useof professionals competent to evaluate the significance andlimitations of its contents and who will accept the responsibilityfor the application of the material it contains. WRI provides theforegoing material as a matter of information and, therefore,disclaims any and all responsibility for application of the statedprinciples or the accuracy of the sources other than materialdeveloped by the Institute.
A Listing ofASTM Standards Applicable to Wire and WWRA 82 Specification for Steel Wire, Plain, for Concrete Reinforcement
A 123 Specification for Zinc (Hot-Dip) Coatings on Iron and Steel Products
A 185 Specification for Steel Welded Wire, Plain, for Concrete Reinforcement
A 370 Test Methods and Definitions for Mechanical Testing of Steel Products
A 496 Specification for Steel Wire, Deformed, for Concrete Reinforcement
A 497 Specification for Steel Welded Wire, Deformed, for ConcreteReinforcement
A 641 Specification for Zinc-Coated (Galvanized) Carbon Steel Wire
A 700 Practices for Packaging, Marking and Loading Methods forSteel Products
A 884 Specification for Epoxy-Coated Steel Wire and Welded Wire forReinforcement
A 933 Specification for Vinyl (PVC) Coated Steel Wire and Welded Wirefor Reinforcement
A 1022 Specification for Deformed and Plain Stainless Steel Wireand Welded Wire for Concrete Reinforcement
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
TF 208-R-03
WWR For Structural ApplicationsA Discussion of Current ProductKnowledge and PracticesINTRODUCTION
With better techniques for assessing ductility, as wellas to increase this property’s presence in the finishedproduct, the trend for WWR is toward higher ductilitywire while maintaining desired minimum yield strengthsand producing larger wire diameters (now up to 3/4”).In fact, recent production research has focused onusing rod sizes that are closer to the finished wiresizes. This reduces the amount of cold-working neededto attain the desired wire size and that, in turn, raisesthe level of ductility.
There are a great many examples of WWR used instructural applications throughout the country, and WRIhas a number of research reports and case studiesavailable that demonstrate how and where highstrength and higher ductility WWR has been used.
With its greater strength, generally higher ductility, andsignificantly lower placing and overall costs, WeldedWire Reinforcement (WWR) offers a highly practicaland cost-efficient alternative to traditional rebar con-crete reinforcement.
WWR may be used in virtually any structural applica-tion-buildings, bridges, highways, tunnels, pipelinesand precast component systems, for instance - thattypically would rely on rebar to fortify concrete. In fact,both ACI and AASHTO have considered WWR compa-rable to rebar for many years, and testing requirements- i.e., tensile, yield strength at various strain rates, andbend testing – are similar for both products. WWR,moreover, adheres to additional required tests, suchas reduction of area (ROA) and wrap and weld sheartesting (with 50% of the samples having the weld inthe center of the gage length).
Ironically, this present-day testing agrees with the morethan 17-year-old data of Allen B. Dove, a prolific engi-neer and honorary member of WRI. Reporting in theSeptember-October 1983 issue of ACI Journal (TitleNo. 80-41), Mr. Dove commented:
“...the wrap test is the best way to prove the fullductility of WWR. When you turn the reinforcement360 degrees around a mandrel either the same sizeas the wire or twice the diameter of the wire, inaccordance with the ASTM Standards, you extendthe outer fibers of the wire more than 50%. That’s atrue test of wire ductility”.
WWR ductility – a measure of the steel wires flexibilityand, therefore, one measure of its ability to withstandlarge strains and redistribute stress – compares veryfavorably with that of rebar. For example, McGillUniversity (Montreal, Quebec, Canada) researcher Dr.Denis Mitchell, attested to WWRs ductility in a report inthe March-April 1994 issue of ACI Structural Journal.“We can provide material which is over 75,000 psiyield strength and will test at 0.35% strain (as ACI hasrequired for many years)”, he wrote, “and it has ductili-ty that matches or exceeds rebar ductility”.
WWR Shearreinforcing with
D4, D8 and D14wire sizes, wasused in the full
length of the 150’bridge girder. -
Lincoln, NE
Welded wire shearcages with D4 andD6.4 wire sizes forconcrete girders inJacobs Field BallPark - Cleveland OH
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 2 • TF 208-R-03
WWR’s strength, flexibility and other advantageshave long been relied upon by the precast industry,particularly for applications that may be subjectedto high flexure and shear stresses. In recent years,with advances in assessment and manufacturingtechnologies, WWR’s use in a broader base ofstructural applications is growing rapidly.
With respect to this greater interest in and growinguse of WWR, the following discussion examinesimportant aspects of this superior product, includingmanufacturing, specifications and applications, han-dling and unloading, placing, coated WWR and met-ric WWR.
MANUFACTURINGFrequently referred to as fabric or wire mesh, WWRis manufactured from hot rolled steel rods. The rodsare cold drawn or cold rolled through a series of diesor carbide rolls to reduce the diameter and toincrease the yield strength of the steel.
WWR for construction is usually manufactured in 5 to8 foot-wide sheets and rolls. Sheets 12’ wide andsome larger are produced primarily for highwaypaving and precast components. Special widths canbe furnished on request. Sheets can be provided upto 40 feet or more in length, but 12-foot 6-inch, 15-feet, 20-feet and 25-feet are the more commonlengths for ease in shipping and placing. Pipe andstandard building fabric are produced in roll form. Moststandard building fabric is available in sheet form.
Wire sizes are available from W1.4-W45 and D4-D45.Other wire sizes are available and vary with individualmanufacturers. The “W” for plain or “D” for deformed
wire numbers are usually whole numbers. For a styledesignation of 12x12-D10xD10, the first set of num-bers is the spacing of wires in inches for both the lon-gitudinal and transverse directions, respectively. Thesecond set is the cross sectional areas of the respec-tive wires in square inches multiplied by 100 (.10 sq.in. x 100 = 10, etc.).
Spacings of longitudinal wires can vary from 2” to 16”(larger spacings are obtainable and vary with individualmanufacturers). Transverse spacings are usually 4, 6, 8,12, or 16”. Wires can be cut flush or have overhangs onthe sides of the welded wire. The ends will generally haveoverhangs of one-half the transverse spacing unlessother multiples of the transverse spacing are requested,i.e. for 12-inch transverse spacing, 6” & 6” or 8” & 4” or10” & 2”, etc.
SPECIFICATIONS AND APPLICATIONSWWR is manufactured in accordance with specifica-tions by the American Society for Testing andMaterials (ASTM). ASTM A82 and A496 specify thestrength and manufacture of plain and deformed wireused in WWR. ASTM A185 and A497 specify the manu-facture and testing of plain and deformed welded wirefor concrete reinforcement.
WWR is manufactured with the wires in either squareor rectangular patterns, referred to as styles, and iswelded by electrical resistance at each intersection.The bond strength of WWR is provided by the weld-ed intersections and deformations when specified.
Welded wire is commonly used to controltemperature/shrinkage stresses and add reservestrength in slabs on grade. The more common orstandard WWR styles are designated: 6x6-W1.4xW1.4, 6x6-W2.1xW2.1, 6x6-W2.9xW2.9 and6x6-W4xW4. Heavier WWR styles utilizing wire diam-eters up to 1/2” (some manufacturers can exceed 1/2”diameter) can be used for structural applications.
The size and area of reinforcement required is speci-fied by the engineer and depends on the slab thick-ness, the spacing of the construction and controljoints, the type and density of the sub base, a frictionfactor for the sub-grade and the yield strength of thewelded wire. There are a number of design methodsused when the WWR is used for strength in the rein-forced concrete slab or structure.
The ACI Building Code (ACI-318) assigns a minimumyield strength (fy) value of 60,000 psi to most steelreinforcing, but allows yield strengths up to 80,000 psifor many design applications.
Wall reinforcingused for precastcorrectional cells -Adult DetentionCenter,
Fairfax County, VA
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 3 • TF 208-R-03
If the rolls or sheets must be lifted by crane at the jobsite, the customer may request the WWR manufacturer toinstall lifting eyes.
Sheet bundles without lifting eyes are placed ondunnage (as specified by the customer) for easierunloading with either a forklift or a crane using a slingchain hooked or threaded through the bundle. At alltimes during off loading of materials, caution must beexercised and all safety regulations and practices mustbe observed.
PLACINGWWR rolls are unrolled, cut to proper length andturned over to prevent ends from curling. Flatteningthe material is best accomplished, mechanically; i.e.,roller straightener, which will provide the necessaryflatness to achieve proper positioning. All WWRshould be placed on support accessories to maintainthe required position and cover as specified by theengineer.
Splices or laps, either structural or temperature/shrinkage types, should be specified by the engineerand in conformance with the ACI Building Code.Typically, structural laps for welded wire fabric are aminimum length of 6” + overhangs for plain wire and8” including overhangs for deformed wires. The Coderequires that one or two cross wires, depending ontype of wire, occur in structural laps of WWR.Deformed wire structural laps, when no cross wiresare included in the splice region, are a minimum of12”. In areas of low stress, splice lengths can bereduced.
For slab on grade construction: With slab thicknessesless than 5”, a single layer of welded wire is placed inthe middle of the slab. For slabs 6” and greater, thetop cover is 1/3 the depth of the slab.
When two layers are specified (usually over 8” thick),the top cover will be 1” to 2” depending on saw cuts
Welded wire reinforcement can be used as ties andstirrups for column, beam and joist cage (confine-ment) reinforcement. WWR cage reinforcement isalso used for concrete encased columns. The WWRsupplier uses a welded wire bending machine toshape the materials into required configurations. Theplacing drawings will identify the location and detailsof the cage assemblies.
When WWR is used for wall reinforcing, form supportaccessories are available to hold the sheets of WWRin place to provide the necessary cover.
HANDLING AND UNLOADINGWWR is shipped in two forms – rolls, usually specified forlight commercial and residential building construction orconcrete pipe, and sheets for general commercial/industrial construction and precast components. If pro-duced in roll form, a number of rolls are unitized in a bun-dle for ease of handling. Individual rolls are securely tied,so uncoiling will not occur when the bundles are cut.
Sheets are bundled in quantities depending on sizeand weight of sheets and in accordance with the cus-tomer’s requirements. Generally, bundles of rolls orsheets will weigh between 2000 and 6000 pounds.Banding is used for shipping stability only. Bundlesshould never be lifted by the steel banding.
WWR Sheet being loaded for truck shipping.
WWR Sheet bundles in route for delivery. 6x6 - W10 x W10 WWR used in bridge redecking. - Albany, NY
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 4 • TF 208-R-03
METRIC WELDED WIRE REINFORCEMENTGenerally, when styles of WWR are converted frominch-pound to metric, both spacings and wire areasare soft metricated and rounded to whole numbers.Pipe fabric is an exception. There will be two lists forboth spacings and wire sizes. One will be a call-outlisting (rounded to whole numbers). The other is anactual spacing or wire size with numbers carried outto 0.1 decimal increments. Examples appear below.
In the future, when more styles are specified in met-ric, wire sizes can be in 5 or 10 square millimeterareas. Keep in mind, all manufacturers can producewire sizes in 1 square millimeter increments (0.001in2). (See Tables 1 & 2)
Examples of styles converted frominch-pound to metric:
Metric Standard style (in-#):152x152-MW 19 x MW 19 (6x6-W 2.9 x W2.9)
Metric Structural style:305x305-MD 71 x MD 71 (12x12-D11 x D11)
Metric Pipe style, Call-out:51x203-MW 77 x MW 32 )2 x 8-W12 x W5)
Metric Pipe style, Actual:50.8x203.2-MW 77.4 x MW 32.3 (2 x 8[W12 x W5)
Note: Conversion factors used: 25.4 mm = 1 inch,645 mm2 = 1 in2 – A reminder, the inch-pound wireareas in the examples are in2 multiplied by 100.
Note: Table 3 is included for use in selecting areasof steel with various wire spacings.
(WWR is placed below the saw cuts). The bottomcover will be 1-1/2” min. on earth or 1” on vapor bar-riers. Support manufacturers produce concreteblocks or steel (coated and uncoated) and plasticchairs, bolsters, and WWR support accessoriesmade specifically for either single layer or doublelayer reinforcing applications.
Placing WWR on appropriately spaced concreteblocks, steel or plastic supports with base plates andtyping the WWR at laps is adequate to maintain it’sposition during concrete placement. WWR should notbe placed on the sub grade and pulled up duringconcrete placement. Following is a suggested guidefor spacing support accessories:
Heavy WWR styles - W9 or D9 and larger: . . . . . . .4’-6’*Medium WWR styles -W5 or D5 to W8 or D8: . . . . . . .3’-4’Light WWR styles - W4 or D4 or less: . . .2’-3’ or less**
* Spacing of supports for WWR with wires larger than W or D9could possibly be increased over the spacings shown dependingon the construction loads applied.**Consider using additional rows of supports when large deflec-tions or deformations occur – also spacing of supports may beincreased provided supports are placed and properly positionedas concrete is needed.
CORROSION RESISTANT WWRThere are several coating specifications for weldedwire reinforcement: one is a vinyl-coated wire andWWR, ASTM A933. There are two types of zinc-coat-ed (galvanized) coatings for wire and WWR. Theyare ASTM A641 (hot-dip process for wire (A 82 and A496) before welding (very popular in the precastpanel industry) - then there is ASTM A123 (hot dipcoating) of the manufactured welded wire sheets.Another coating is ASTM A884 - a fusion bondedepoxy-coating applied to the welded wire sheets.Now, there is an ASTM standard for stainless steelwire and WWR. It is ASTM A1022-02.
Wide spaced 12x12 - D7xD7 WWR for slab on grade construction to obtainproper positioning in this auto parts distribution facility in Zanesville, OH.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
*Metric wire sizes can be specified in 1 mm2 increments. **Inch-Pound sizes can be specified in .001 in2 increments.Note ✧ - For other available wire sizes, consult other WRI publications or discuss with WWR manufactures.Note ✦ - Wires may be deformed, use prefix MD or D, expect where only MW or W is required by building codes (usually less
than MW26 or W4).
GageGuide
7/0
6/0
5/0
4/0
3/0
2/0
1/0
1
2
3
4
6
8
10
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 6 • TF 208-R-03
COM
MO
N S
TYLE
S O
F M
ETRI
C W
ELD
ED W
IRE
REIN
FORC
EMEN
T (W
WR)
WIT
H E
QU
IVA
LEN
T U
S CU
STO
MA
RY U
NIT
S3
A1
Met
ric
Sty
les
Wt.
Eq
uiv
alen
t U
SA
1W
t(m
m2 /
m)
(MW
= P
lain
wir
e)2
(kg
/m2 )
Cu
sto
mar
y S
tyle
(in
2 /ft
)(l
bs/
CS
F)
A1
& 4
88.9
102x
102
- M
W9x
MW
91.
514x
4 -
W1.
4xW
1.4
.042
3112
7.0
102x
102
- M
W13
xMW
132.
154x
4 -
W2.
0xW
2.0
.060
4418
4.2
102x
102
- M
W19
xMW
193.
034x
4 -
W2.
9xW
2.9
.087
6225
4.0
102x
102
- M
W26
xMW
264.
304x
4 -
W4.
0xW
4.0
.120
8859
.315
2x15
2 -
MW
9xM
W9
1.03
6x6
- W
1.4x
W1.
4.0
2821
84.7
152x
152
- M
W13
xMW
131.
466x
6 -
W2.
0xW
2.0
.040
3012
2.8
152x
152
- M
W19
xMW
192.
056x
6 -
W2.
9xW
2.9
.058
4216
9.4
152x
152
- M
W26
xMW
262.
836x
6 -
W4.
0xW
4.0
.080
58
B1
196.
910
2x10
2 -
MW
20xM
W20
3.17
4x4
- W
3.1x
W3.
1.0
9365
199.
015
2x15
2 -
MW
30xM
W30
3.32
6x6
- W
4.7x
W4.
7.0
9468
199.
030
5x30
5 -
MW
61xM
W61
3.47
12x1
2 -
W9.
4xW
9.4
.094
7136
2.0
305x
305
- M
W11
0xM
W11
06.
2512
x12
- W
17.1
xW17
.1.1
7112
8
C1
342.
915
2x15
2 -
MW
52xM
W52
5.66
6x6
- W
8.1x
W8.
1.1
6211
635
1.4
152x
152
- M
W54
xMW
545.
816x
6 -
W8.
3xW
8.3
.166
119
192.
630
5x30
5 -
MW
59xM
W59
8.25
12x1
2 -
W9.
1xW
9.1
.091
6935
1.4
305x
305
- M
W10
7xM
W10
79.
7212
x12
- W
16.6
xW16
.6.1
6612
5
D1
186.
315
2x15
2 -
MW
28xM
W28
3.22
6x6
- W
4.4x
W4.
4.0
8863
338.
715
2x15
2 -
MW
52x5
25.
616x
6 -
W8x
W8
.160
115
186.
330
5x30
5 -
MW
57xM
W57
3.22
12x1
2 -
W8.
8xW
8.8
.088
6633
8.7
305x
305
- M
W10
3xM
W10
35.
6112
x12
- W
16xW
16.1
6012
0
E1
177.
815
2x15
2 -
MW
27xM
W27
3.08
6x6
- W
4.2x
W4.
2.0
8460
317.
515
2x15
2 -
MW
48xM
W48
5.52
6x6
- W
7.5x
W7.
5.1
5010
817
5.7
305x
305
- M
W54
xMW
543.
0812
x12
- W
8.3x
W8.
3.0
8363
317.
530
5x30
5 -
MW
97xM
W97
5.52
12x1
2 -
W15
xW15
.150
113
1G
roup
A-
Com
pare
s ar
eas
of W
WR
at
a m
inim
um f
y=
65,
000
psi.
Gro
up B
- C
ompa
res
area
s of
WW
R a
t a
min
imum
fy
= 7
0,00
0 ps
i G
roup
C -
Com
pare
s ar
eas
of W
WR
at
a m
inim
um f
y=
72,
500
psi
Gro
up D
- C
ompa
res
area
s of
WW
R a
t a
min
imum
fy
= 7
5,00
0 ps
i G
roup
E -
Com
pare
s ar
eas
of W
WR
at
a m
inim
um f
y=
80,
000
psi
2 Wire
s m
ay a
lso
be d
efor
med
, us
e pr
efix
MD
or
D,
exce
pt w
here
onl
y M
W o
r W
is r
equi
red
by b
uild
ing
code
s (u
sual
ly le
ss t
han
a M
W26
or
W4)
. A
lso
wire
siz
es c
an b
e sp
ecifi
ed in
1m
m2
(met
ric)
or .
001
in.2
(US
Cus
tom
ary)
incr
emen
ts.
3 For
oth
er a
vaila
ble
styl
es o
r w
ire s
izes
, co
nsul
t ot
her
WR
I pu
blic
atio
ns o
r di
scus
s w
ith W
WR
man
ufac
ture
rs.
4 Sty
les
may
be
obta
ined
in r
oll f
orm
. N
ote:
It
is r
ecom
men
ded
that
rol
ls b
e st
raig
hten
ed a
nd c
ut t
o si
ze b
efor
e pl
acem
ent.
TABL
E 2
with
are
as o
f #3
or
#4 r
ebar
at
12”
o.c.
at m
inim
um f
y=
60,
000
psi
}
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
U.S. CUSTOMARY (INCH-POUND) WIRE SIZES AND AREASTABLE 3 - SECTIONAL AREAS OF WELDED WIRE REINFORCEMENT
Wire Size Number* Nominal Nominal Area in Sq. In. Per Ft. Of Width For Various Spacing(area of steel x 100) Diameter Weight Center-To-Center Spacing
Note: The above listing of plain wire sizes represents wires normally selected to manufacture welded wire reinforcement styles to specific areas of reinforcement. Wires may bedeformed using prefix D, except where only W is required on building codes (usually less than W4). Wire sizes other than those listed above may be available if the quantityrequired is sufficient to justify manufacture.*The number following the prefix W identifies the cross-sectional area of the wire in hundredths of a square inch.The nominal diameter of a deformed wire is equivalent to the diameter of a plain wire having the same weight per foot as the deformed-wire.Refer to ACI 318 for The ACI Building Code requirements for tension development lengths and tension lap splices of welded wire reinforcement. For additional informa-tion see Welded Wire Reinforcement Manual of Standard Practice and Structural Welded Wire Reinforcement Detailing Manual, both published by the WireReinforcement Institute.
This report is furnished as a guide to industry practice. The Wire Reinforcement Institute (WWR) and itsmembers make no warranty of any kind regarding the use of this report for other than informational purposes.This report is intended for the use of professionals competent to evaluate the significance and limitations of itscontents and who will accept the responsibility for the application of the material it contains. WRI provides theforegoing material as a matter of information and, therefore, disclaims any and all responsibility for applicationof the stated principles or the accuracy of the sources other than material developed by the Institute.
Page 7 • TF 208-R-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
For a complete up to date listingof WRI members, e.g. producers,associates, professional, honoraryand life members - call or write tothe WRI. The WRI staff would alsolike to answer your questions anddiscuss your needs about specificreinforcement requirements onindividual projects.
This report is furnished as a guide to industry practice. TheWire Reinforcement Institute (WRI) and its members make nowarranty of any kind regarding the use of this report for otherthan informational purposes. This report is intended for the useof professionals competent to evaluate the significance andlimitations of its contents and who will accept the responsibilityfor the application of the material it contains. WRI provides theforegoing material as a matter of information and, therefore,disclaims any and all responsibility for application of the statedprinciples or the accuracy of the sources other than materialdeveloped by the Institute.
Structural WWR used in box culverts.
Applications for WWR ReinforcedConcrete Components and Structures
Bridge “I” girders have WWR shearreinforcement the full length.
Large cages of WWR confinementreinforcement for high rise buildings.
A skip pan joist and slab floor system with high strength WWR.
Page 8 • TF 208-R-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
TABLE 2ASTM AND CSA PROPERTIES OF STEEL WIRE IN WELDED WIRE REINFORCEMENT
Type of WWR Minimum Tensile Minimum Yield2 Weld ShearStrength Strength
MPa psi MPa psi MPa psi
Welded Wire Reinforcement, Plain 520 75,000 450 65,000 241 35,000Welded Wire Reinforcement, Deformed 550 80,000 485 70,000 241 35,0001Rebar sizes of #3, #4, #5 and #6 are not available in strengths higher than 420 MPa.2For use of WWR with higher minimum yield strengths see the section on Minimum Yield Strengths.
TF 209-03 Metric
INTRODUCTIONThis Tech Fact* provides basic information on cold-worked wire and welded wire reinforcement (WWR) toassist in the design and detailing of WWR systems forconcrete structures. Tables are included to comparemetric steel areas and diameters for reinforcement witha minimum yield strength of 420 MPa and three higherminimum yield strengths, i.e., 485 MPa, 515 MPa and550 MPa, for WWR1. Tables 3-6 consider steel wirediameters ranging from 5 mm to 16 mm.
The American Concrete Institute‘s (ACI) publication318M ACI 318, Building Requirements for StructuralConcrete defines deformed reinforcement for structuralconcrete in Section 2.1. The section states that weldedplain wire reinforcement, welded deformed wire rein-forcement and deformed wire are defined as deformedreinforcement. For further definition and acceptance forthe use of high strength reinforcement see 318M ACI318, Chapter 3.
Design Aids For Structural Welded WireReinforcement (Metric Units for WWR/Rebar Comparison Tables)
SPECIFICATIONSThe American Society for Testing and Materials(ASTM) publishes specifications for the wire used tomanufacture reinforcement and for both plain anddeformed WWR. The Canadian Standards Association(CSA) publishes similar specifications for use inCanada. The appropriate titles and numbers are givenin Table 1. These are considered to be the governingspecifications for both wire and WWR. Federal, Stateand local governmental agencies have special specifi-cations that will control. The AASHTO specificationnumbers are a prime example of this. They are alsostated in Table 1. Table 2 has minimum strength prop-erties and weld shear test values. See the section onMinimum Yield Strengths for specific references to highstrength reinforcement.
U.S. AASHTO CanadianSpecifications Specifications Standard Title
ASTM A 82 M32 CSA G 30.3 Steel Wire, Plain, for Concrete ReinforcementASTM A 185 M55 CSA G 30.5 Steel Welded Wire Reinforcement, Plain, for ConcreteASTM A 496 M225 CSA G 30.14 Steel Wire, Deformed, for Concrete ReinforcementASTM A 497 M221 CSA G 30.15 Steel Welded Wire Reinforcement, Deformed, for Concrete
*This Tech Fact may be inserted in the WRI Structural Detailing Manual, Chapter 2 and will be updated as manufacturing capabilities are changed.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 2 • TF 209-03 Metric
MINIMUM YIELD STRENGTHSThe yield strength values shown in Table 2 are ASTM and CSA requirements for minimum yield strengths meas-ured at a strain of 0.5% of gage length. The 318M ACI 318 Structural Building Code, Chapter 3, states that mini-mum yield strength values greater than 420 MPa up to 550 MPa may be used, provided they are measured at astrain of 0.35% of gage length. The ACI strain requirements are now covered in supplements specified by ASTMand CSA. Also, the 318M ACI 318 Building Code limits the minimum design yield strength of reinforcement to 550MPa (Chapter 9, 9.4), (Chapter 11, 11.5.2).
WELD SHEAR STRENGTH AND CONCRETE BONDPlain WWR develops bond with the concrete through the positive mechanical anchorage at each welded intersec-tion of wires. Deformed WWR utilizes wire deformations along with the welded intersections for bond and anchor-age. The ASTM and CSA requirements for weld shear strength at the wire intersections are shown in Table 2.
ASTM and CSA specify a size differential for wires being welded together to assure adequate weld shear strength.For welded wire reinforcement, plain and deformed, the smaller wire must have an area of 40 percent or more ofthe area of the larger wire.
EXAMPLE: (Showing Use of Comparison Tables 3-6)Parameters:fy = 550 MPa to be used in lieu of fy = 420 MPa reinforcing bars. The slab is for one-way stress calculations, 150mm thick.
The positive moment reinforcement is 13 mm bars @ 250 mm c/c (As = 508 mm sq./m width)The temperature reinforcement is 13 mm bars @ 450 mm c/c (As = 282 mm sq./m width)
The negative moment reinforcement is 16 mm bars @ 300 mm c/c (As = 656 mm sq./m)Use Table 6 - Reinforcing Bar: fy = 420 MPa, Welded Wire Reinforcement: fy = 550 MPaBegin with 150 mm spacings and adjust as necessary.The parameters noted above are followed in these derivations:
Aw = 656 x 420 x 150 = 75.1mm2, then db = 75.1 = 9.8mm - ok550 1000 0.7854
Cross wires: 75.1 x 0.4 = 30.1mm2, then db = 30.1 = 6.2mm - Select 400mm spacings0.7854
The style of WWR sheet for the negative moment reinforcement (top) is: 150 x 400 - 9.8 x 6.2
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
REMARKS:When the WWR style is required to furnish tension reinforcement in only one direction, the cross-wire should bethe smallest size permitted at the maximum spacing permitted. ASTM and CSA specify the minimum size as notedabove. The maximum spacing is 3 times the slab thickness or 450 mm as specified in ACI 318, Chapter 7.
NOTES FOR TABLES 3-61. Mass in kg/m2 is for one direction only. Double the weight for the same reinforcing in the other direction, or
add the appropriate weight for a different pattern in the other direction.
2. Mass in kg/m2 is theoretical and are intended for estimating purposes only. Contact the WWR producers formore specific project requirements.
3. ACI 318 requires the minimum deformed wire diameter to be 5.7 mm for structural applications. Sheets ofWWR can be both deformed and plain mixed. (ACI 318, Chapter 12, 12.7.4).
4. In accordance with ACI 318, the maximum spacing permitted for plain WWR is 300 mm and the maximumspacing for deformed welded wire reinforcement is 400 mm. The 450 mm spacing in the tables is only rec-ommended for use in slab on grade applications, which are not governed by ACI 318, unless designed as astructural slab.
WRI provides the material herein as a matter of information and therefore, disclaims any and all respon-sibility for application of the stated principles or the accuracy of the data other than material developedby the institute.
Definition of expressions:As - Area of steel (per meter width or per foot of width)
Aw- Area of wire
db - diameter of bar or wire
Conversions – Inch-Pound to Metric Measurements Inch-pound (psi) S.I. Units (MPa) Metric (kg/cm2)
Bar Spacing Wire Diameter (mm) at Various Spacing (mm)#4 Rebar @ 420 MPa Welded Wire Reinforcement @ 550 MPa
#5 Rebar @ 420 MPa Welded Wire Reinforcement @ 550 MPaBar Spacing Wire Diameter (mm) at Various Spacing (mm)
#3 Rebar @ 420 MPa Welded Wire Reinforcement @ 550 MPaSpacing Wire Diameter (mm) at Various Spacing (mm)
#6 Rebar @ 420 MPa Welded Wire Reinforcement @ 550 MPaBar Spacing Wire Diameter (mm) at Various Spacing (mm)
Page 7 • TF 209-03 Metric
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE® 942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
TABLE 2ASTM AND CSA PROPERTIES OF STEEL WIRE IN WELDED WIRE REINFORCEMENT
Type of WWR Minimum Tensile Minimum Yield2 Weld ShearStrength Strength
MPa psi MPa psi MPa psi
Welded Wire Reinforcement, Plain 520 75,000 450 65,000 241 35,000Welded Wire Reinforcement, Deformed 550 80,000 485 70,000 241 35,0001Rebar sizes of #3, #4, #5 and #6 are not available in strengths higher than 60,000 psi (Grade 60).2For use of WWR with higher minimum yield strengths see the section on Minimum Yield Strengths.
TF 209-R-03
INTRODUCTIONThis Tech Fact* provides basic information on cold-worked wire and welded wire reinforcement (WWR) toassist in the design and detailing of WWR systems forconcrete structures. Tables are included to comparesteel areas for reinforcement with a minimum yieldstrength of 60,000 psi and three higher minimum yieldstrengths, i.e., 70,000, 75,000 and 80,000 psi, forWWR.1 Tables 3-6 consider steel wire sizes rangingfrom W1.4 (1/8”φ to W or D 45 (3/4”φ).
The American Concrete Institute‘s (ACI) publicationACI 318, Building Requirements for StructuralConcrete defines deformed reinforcement for structuralconcrete in Section 2.1. The section states that weldedplain wire reinforcement, welded deformed wire rein-forcement and reinforcement are defined as deformedreinforcement. For further definition and acceptance forthe use of high strength reinforcement see ACI 318,Chapter 3.
Design Aids For Structural Welded WireReinforcement (includes WWR/Rebar Comparison Tables)
SPECIFICATIONSThe American Society for Testing and Materials(ASTM) publishes specifications for the wire used tomanufacture reinforcement and for both plain anddeformed WWR. The Canadian Standards Association(CSA) publishes similar specifications for use inCanada. The appropriate titles and numbers are givenin Table 1. These are considered to be the governingspecifications for both wire and WWR. Federal, Stateand local governmental agencies have special specifi-cations that will control. The AASHTO specificationnumbers are a prime example of this. They are alsostated in Table 1. Table 2 has minimum strength prop-erties and weld shear test values. See the section onMinimum Yield Strengths for specific references to highstrength reinforcement.
U.S. AASHTO CanadianSpecifications Specifications Standard Title
ASTM A 82 M32 CSA G 30.3 Steel Wire, Plain, for Concrete ReinforcementASTM A 185 M55 CSA G 30.5 Steel Welded Wire Reinforcement, Plain, for ConcreteASTM A 496 M225 CSA G 30.14 Steel Wire, Deformed, for Concrete ReinforcementASTM A 497 M221 CSA G 30.15 Steel Welded Wire Reinforcement, Deformed, for Concrete
*This Tech Fact may be inserted in the WRI Structural Detailing Manual, Section 2 and will be updated as manufacturing capabilities are changed.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 2 • TF 209-R-03
MINIMUM YIELD STRENGTHSThe yield strength values shown in Table 2 are ASTMand CSA requirements for minimum yield strengthsmeasured at a strain of 0.5% of gage length. The ACI318 Structural Building Code, Chapter 3, states thatyield strength values greater than 60,000 psi to 80,000psi may be used, provided they are measured at astrain of 0.35% of gage length. The ACI strain require-ments are now covered in supplements specified byASTM and CSA. Also, the ACI 318 Building Code limitsthe minimum design yield strength of reinforcement to80,000 psi (Chapter 9, 9.4), (Chapter 11, 11.5.2).
WELD SHEAR STRENGTH AND CONCRETE BONDPlain WWR develops bond with the concrete throughthe positive mechanical anchorage at each weldedintersection of wires. Deformed WWR utilizes wiredeformations along with the welded intersections forbond and anchorage. The ASTM and CSA require-ments for weld shear strength at the wire intersectionsare shown in Table 2.
ASTM and CSA specify a size differential for wiresbeing welded together to assure adequate weld shearstrength. For welded wire reinforcement, plain anddeformed, the smaller wire must have an area of 40percent or more of the area of the larger wire.
EXAMPLE: (Showing Use of Comparison Tables 3-6)Select the styles of WWR with minimum yield strength,fy = 80,000 psi to be used in lieu of fy = 60,000 psi(Grade 60) reinforcing bars. The slab is for a one-wayslab, 6 inches thick.The positive moment reinforcementis #4 bars @ 10” c/c. (As = .24 in2)The temperature reinforcementis #4 bars @ 18” c/c. (As = .133 in2)The negative moment reinforcementis #5 bars @ 12” c/c. (As = .31 in2)
Use Table 6-Reinforcing Bar: fy = 60,000 psi,WeldedWire Reinforcement: fy = 80,000 psiBegin with 6 in. by 6 in. WWR spacing and adjust asnecessary.
POSITIVE MOMENT REINFORCEMENT#4 bars @ 10 in. c.c. - select W9 wire @ 6 in.
TEMPERATURE REINFORCEMENT#4 bars @ 18 in. c.c. - select W5 wire @ 6 in.
Since W5 wire is greater than 40% of W9 wire, the min-imum wire size requirement by ASTM is satisfied.Reviewing Table 6 (WWR with fy =80,000 psi) checkthe amount of temperature reinforcement required,compared to #4 @ 18” (fy =60,000 psi). For a 6 inchslab, W5 wire @ 6 in. furnishes the desired steel area.
The WWR style for the bottom reinforcement (positivemoment) is then: 6 x 6 - W9 x W5.
NEGATIVE MOMENT REINFORCEMENT#5 bars @ 12 in. c.c. - select W11.6 wire @ 6 in.
REMARKS:When the WWR style is required to furnish tensionreinforcement in only one direction, the cross-wireshould be the smallest size permitted at the maximumspacing permitted. ASTM and CSA specify the mini-mum size as noted above. The maximum spacing is 3times the slab thickness or 18” as specified in ACI 318,Chapter 7.
Cross-wire: 40% of W11.6 = W5 wire @ 12 in. (ASTMA185, Chapter 7). Use W5 wire @ 12 in. for efficiency,since it is the same size used in the positive momentreinforcement. The WWR style for the top reinforce-ment (negative moment) is then: 6 x 12 - W11.6 x W5.
NOTES FOR TABLES 3-61. Weights per 100 square feet are for one directiononly. Double the weight for the same reinforcing in theother direction, or add the appropriate weight for adifferent pattern in the other direction.2. Weights per 100 square feet are theoretical and areintended for estimating purposes only. Contact the WWRproducers for more specific project requirements.3. W (plain) or D (deformed) are used as prefixes forwire sizes (ex:W8, D10). ACI 318 requires the minimumD-deformed wire to be D4 for structural applications.Sheets of WWR can be both D and W mixed.(ACI 318, Chapter 12, 12.7.4).4. In accordance with ACI 318, the maximum spacingpermitted for plain WWR (W) is 12 inches, and themaximum spacing for deformed welded wire reinforce-ment (D) is 16 inches. The 18-inch spacing in thetables is only recommended for use in slab on gradeapplications, which are not governed by ACI 318.
WRI provides the material herein as a matter ofinformation and therefore, disclaims any andall responsibility for application of the statedprinciples or the accuracy of the data other thanmaterial developed by the institute.
As = .20 x 12 x 60 ÷ 2 = 0.09 in2
10 80
As = .20 x 12 x 60 ÷ 2 = 0.05 in2
18 80
As = .31 x 60 ÷ 2 = .116 in2
80
WRI provides the material herein as a matter of information and therefore, disclaims any and all responsibility for application of the stated principles or the accuracy of the data other than material developed by the institute.
Rebar Rebar Wire Sizes For Various Spacings WWR WWRBARS As #/CSF 4 IN. 6 IN. 8 IN. 12 IN. 16 IN. 18 IN. As #/CSF
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
TF 306-R-03
Concrete pipe producers everywhere have long relied onwelded wire reinforcement (WWR) in the manu-facture of their products. Government agencies andprivate developers have come to rely on the structuralintegrity and performance of these products to pro-vide a safe and healthy living environment. Theproducers of WWR continue to play an importantrole in the ever expanding proven track record ofreinforced concrete pipe by supplying qualitymaterials in the most efficient configurations.
This document is intended to provide sound recommen-dations for use in estimating the reinforcing steel in aconcrete pipe. The information on the following pageswas compiled using the published reinforcing designs ofthe American Society for Testing and Materials “StandardSpecification for Reinforced Concrete Culvert, StormDrain, and Sewer Pipe,” Designation C 76
WWR for the reinforced concrete pipe (RCP) industry isproduced in accordance with ASTM A 82 and A 185 forPlain Wire and Plain Welded Wire Fabric Reinforcement,respectively, and ASTM A 496 and A 497 for DeformedWire and Deformed Welded Wire Fabric Reinforcement,respectively. The RCP industry uses a unique nomen-clature when describing WWR that is different from mostother reinforced products. The wires providing the struc-tural integrity to the pipe run circumferentially withinthe pipe wall. These wires are referred to as circum-ferential wires. The wires which run from spigot tobell, or tongue to groove, are called cross wires.
Although C 76 does not require any longitudinal rein-forcement in the pipe, cross wires are present primarilyfor three reasons. First, the cross wires provide assur-ance that the circumferential wires remain at the correctspacing during cage fabrication and pipe casting.Second, the cross wires provide support for the freshlycast pipe while it cures. Third, a minimum cross wirearea equal to 40% of the circumferential wire area isrequired by ASTM specifications A 185 and A 497 toensure strong welds.
The tables on the following pages list only the most com-mon styles used throughout the RCP industry today.They are also some of the most efficient. Here are theconventions that were used to develop these tables:
• The minimum cross wire size is W2.5.• Cross wire spacing in single cage pipe is 6 inches,
and in double cage pipe is 8 inches.• Maximum circumferential wire size is W12.• Wire size increments are by half W-number.• Only B-wall and C-wall, Class II through Class V
designs are shown.• Weights were calculated using a fabric width of 93”
(+1,+1) for 3” spaced styles, and a width of 94”(+1,+0) for 2” spaced styles for pipe with a layinglength of 8’-0”.
• Expandable bell reinforcing cages were excluded.• Cage lengths were calculated to provide 1” clear
cover, a minimum 2” welded lap, then rounded tothe next higher cross wire space.
• Elliptical cage configurations are not shown.• Elliptical areas are shown for reference only.
Wire sizes are based on nominal diameters and/orweights per LF. Tolerances per ASTM A 82 and A496 apply. The user of this document is responsiblefor making any adjustments necessary to meetspecific conditions, should they differ from theseconventions. Wire size increments of 0.1 W-numberand sizes larger than W12 are available upon request. C76 provides the RCP producer with several pro-visions regarding reinforcing cage configuration.The tables on the following pages take advantage ofall these provisions to arrive at the most efficientcage configuration possible with the conventionslisted. One such provision is found in C 76 Table 4,footnote B, which states that C-wall 24-in. to 33-in.diameter pipe may utilize a single cage having anarea not less than the sum of the inner and outerspecified areas. This provision creates efficienciesover the standard two-cage design simply becausethere is one less cage to fabricate.
A similar provision is found in two places in C 76.Tables 2 and 3, footnote E permits the use of a singlereinforcing cage for 36-in. diameter B-wall and C-wall pipe, but calls out specific areas to be met.
Another provision is found in all the tables underfootnote B which permits the use of quadrant mats.This may very well be the single most economicalconfiguration available in the C 76 specification.This provision is used primarily where steel areasabove 0.60 in. 2 per linear foot are required. Whenapplied to both the inner and outer cages, steelsavings can range from 20% to 37%. Figures 1 and 2illustrate the concept of quadrant mat reinforcing. Very
WELDED WIRE REINFORCEMENT FOR CIRCULAR CONCRETE PIPE
simply, this provision allows the producer to concentratethe placement of the steel to the regions or "quadrants"of the pipe wall where it is needed. When a concretepipe is loaded, tension develops in the crown and inverton the inside face of the pipe wall, and at the springlineon the outside face of the pipe wall. The quadrant matsare placed in these areas to resist the tensile forces thatdevelop. Opposite these locations the pipe wall is incompression, which the concrete alone can resist. Thetypical quadrant mat configuration consists of a full cir-cular cage having an area of at least 25% of the speci-fied area for that cage, with the remaining area provided byeach of two 90o quadrant mats placed as shown inFigure 1. The combined areas of the full circular cage andeither single quadrant mat must be equal to or greater thanthe area specified for that cage.
A more practical quadrant mat configuration is the useof a "quadrant cage" and a single quadrant mat (Figure2). The quadrant cage is rolled 11/4 turns (450o) andoverlapped by 90° to include the first "quadrant mat".Then a single 90° quadrant mat is rolled and placedopposite the 90° overlap. The quadrant cage and quad-rant mat are rolled from the same style which is at least50% of the specified cage area. Where the overlapoccurs and where the quadrant mat is placed, the totalarea is equal to or greater than the specified cage area.When this configuration is used, labor is minimized anda steel savings of up to 25% is realized. This quadrantcage (QC) and quadrant mat (QM) configuration is usedthroughout the following tables where specified areasexceed 0.60 in.2 per linear foot of pipe wall.
Probably the least understood provision in C76 isfound under Permissible Variations Section 12.5.2 –Area of Reinforcement. It uses the alternate ellipticalcage area listed in the table for a given pipe diameterand class to calculate the permissible variations of theinner and outer cages. It states that when inner andouter circular cages are used, the area of the inner cagemust be at least 85% of the specified alternate ellipticalcage area and the area of the outer cage must be atleast 51% of the elliptical area, but the total area of theinner and outer cages must be at least 140% of the ellip-tical area. This allows for small adjustments in the innerand outer cage areas that can result in savings of near-ly 10% (see page 10 – 66" Class III C-wall design). Thedesigns created using Permissible Variations Section12.5.2 are identified by a u in the following tables.
The format of the tables on the following pages hasbeen revised from previous printings of this Tech Fact.The left third of each table lists the design requirementsof ASTM C 76-97, including diameter, class, 0.01-inchcrack and ultimate D-Loads, wall designation and thick-ness, and concrete strength. The center third lists theinner cage data, including minimum area required, wirespacing, wire size, cage length, and cage weight per lin-
ear foot of pipe. The right third lists the correspondingouter cage data, and along the far right side of eachtable is the total cage weight per linear foot of pipe andthe specified alter-nate elliptical cage area used inSection 12.5.2 calculations.
The purpose of this document is to provide guidanceand suggestions for reinforcing configurations that meetthe minimum reinforcing requirements of the ASTM C76-97 Specification. Naturally there are many otherconfigurations available to the concrete pipe producerfor their use. These are simply the most common beingused in today’s market.
Contact a WRI member producer for specific requestsand conditions that are not addressed in this document.Styles and wire sizes other than those shown in thetables are available upon request. This Tech Fact wasprepared under the direction of the Pipe FabricCommittee of the Wire Reinforcement Institute, Inc.
Publication ofthe data hereinis not intendedas a warrantyon the part ofthe WireReinforcementInstitute, Inc. orits memberc o m p a n i e s ,with respect toits suitability forany general orparticular use,or of freedomfrom infringe-ment on anyexisting patentor patents. Theuser assumesall liability aris-ing from anysuch contin-gencies.
Note: In the following tables, where quadrant designs appear below an alternate design identified by a ◆ , the quadrant design represents the alternate design.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
Principles of ReinforcementWhen concrete pipe is subjected to a load, either by a testingapparatus or a field installation, this load tries to deform thepipe into an elliptical shape. During the loading process tensilestresses develop on the inside of the pipe at the crown andinvert and on the outside of the pipe at the springline, and com-pressive stresses develop opposite these tensile stresses (Fig.1). Since concrete is strong in compression but weak in ten-sion, cracks form in the tensile zones. Steel reinforcement inthe form of welded wire is used to hold these cracks together,and thus provide structural integrity to the pipe. Although steelreinforcement is not required in the compression zones of thepipe wall, modern manufacturing techniques preclude the steelfrom being left out of these areas.
D-Load Requirements &Manufacturing SpecificationsReinforced concrete pipe is manufactured in accordance withASTM C-76 & 76M (CSA Standard A-257.2 M). The strengthof concrete pipe is stated in terms of D-load which is the loadin newtons per linear meter per millimeter of diameter (pounds-force per linear foot per foot of diameter). Concrete pipe that istested by the three-edge-bearing method is classified accord-ing to the D-load that produces a 0.3 mm crack, and the high-er D-load that will produce minimum ultimate strength. The D-load strength concept and the statistical evaluation of testresults are the basis for the ASTM and CSA Standards thatgovern the manufacture of concrete pipe. ASTM C76 & C76M(CSA A-257.2 M) lists design tables for 5 Classes of reinforcedconcrete pipe (i.e. 40-D through 140-D) showing the pipe diam-eter, wall thickness, compressive strength of concrete and theamount of circumferential reinforcement required for eachclass. The steel areas listed are typically minimum required ifdesigned by C76 specifications, however, the overridingacceptance factor is normally the three-edge-bearing test. Forsome larger pipe sizes where the ASTM & CSA Standards donot list steel areas, the pipe manufacturer may employ the indi-rect design method as a guide to selecting steel areas. As analternate to the designs requiring both inner and outer circular cages, the reinforcement may be positioned andproportioned with combinations of circular cages, elliptical cages and quadrant steel mats within the minimum limitsspecified. Figure 2 illustrates a typical reinforcement pattern for large diameter pipe combining an inner and outercage with an elliptical cage for optimum positioning of tensile steel.This publication is furnished as a guide for the selection of welded wire reinforcement with the understanding that while every effort has been made to insure accuiracy, neither the Wire ReinforcementInstitute, Inc., nor its member companies make any warranty of any kind respecting the use of the publication for other than informational purposes.
Steel ReinforcementCircular reinforcing wire cages are fabricated from pre-manufactured welded wire reinforcement which isrolled or rerolled into the required cage diameter and tack welded. The wire used in pipe fabric is producedfrom controlled-quality, low carbon hot rolled steel rods. These rods are cold worked through a series of diesto reduce the rod diameter to the specified wire diameter, thus increasing the overall strength of the steel.A deformation roll is added to produce deformed wire. Chemical composition is carefully selected to giveproper welding characteristics in addition to desired mechanical properties. Welded wire reinforcement isproduced on automatic welding machines which are designed for long, continuous operation. Longitudinalwires are straightened and fed continously through the machine. Transverse wires, entering from the sideor from above the welder, are resistance welded to the longitudinal wires each time the longitudinal wiresadvance through the machine. Wire and welded wire pipe fabric reinforcement is tested in strict confor-mance with ASTM A370 requirements.
Wire Size DesignationIndividual wire (plain and deformed) size designations are based on the cross-sectional area of a given wire.The "W" prefix designates plain wire and "D" designates deformed. The number following the letter givesthe cross-sectional area of the wire (for customary units, in hundredths of a square inch). For example, W4would indicate a plain wire with a cross-sectional area of 0.04 in2. D4 would indicate a deformed wire withan area of 0.04 in2. When describing metric welded wire a prefix "M" is added with the number following theletters "MW" or "MD" denoting the steel area in mm2. For example MW or MD26 refers to an area of 26 mm2.The enclosed pipe fabric Table 4 lists typical W and equivalent MW wire sizes along with wire areas, diam-eters & mass (weight) per unit length of wire.
Designating Style Of Welded Wire ReinforcementSpacings and sizes of wires in welded wire reinforcement are identified by "style". A typical style designa-tion is 2x8 - W12xW5. Here is a description of the numbers in the style:
•Spacing of longitudinal wire = 2" (51 mm)•Spacing of transverse wires = 8" (203 mm)•Size of longitudinal wires = W12 size (77 mm2)•Size of transverse wires = W5 size(32 mm2)
The equivalent metric (call out) designation would be 51x203 - MW77xMW32. Note both wire spacings andwire sizes are soft metricated, then rounded to whole numbers.
Calculating Weights (Mass) from Actual Wire DimensionsWhen figuring widths, lengths and weights of pipe fabric use the actual metric soft conversions for wire spac-ings and sizes in Table 4. Due to the approximation of conversion factors and multipliers, when soft con-verting from metric styles to inch-pound styles or vice versa, calculated weights (mass) and areas of finishedproducts, e.g., rolls and sheets, may vary by as much as 1%. Where there is a variance, the inch poundcalculations govern. An example follows:
Consider the following inch-pound call-out width and length for calculating weights (mass) in this example: width = 92" + 1/2" + 1/2" overhangs (2337mm + 13mm + 13mm overhangs)length = 600 feet including 4" overhangs (183m incl. 102mm overhangs)
When figuring weights (mass) of total products, e.g., rolls or sheets use actual (soft converted) wire spac-ings and sizes, width and length.
Example: Wire Size Mass (kg/m) No. of Wires Length (L) or Total MassOverall Width (OW)
Long. wires(circumferential) MW77.4 .607 x x L=182.88m = 5217.38
Cross Wires(longitudinal) MW32.3 .253 x x OW=2.36m = kg/roll
2336.8=46spc.(47wires)50.8
18288 = 900203.2
537.37 5754.75
Page 2 • TF 311-M-03
www.wirereinforcementinstitute.org
Page 3 • TF 311-M-03
Industry Method of Designating Style:Example - 51x203-MW77xMW32 (2x8 W12xW5)
Longitudinal Longitudinalwire spacing wire size
Transverse Transversewire spacing wire size
*(referred in the concrete pipe industry as circumferential wire)†(referred in the concrete pipe industry as longitudinal wire)
Side Overhangs may be varied as required and do not need to be equal. Overhang lengths limitedonly by overall sheet width.
End Overhangs-Thesum of the end overhangsshould equal onetransverse wire space.Unless otherwisespecified, each endoverhang equals one-halfof a transverse space.
Longitudinal wireTransverse wire
Overall W
idth
Width
Length
Specifications
Welded wire reinforcement and wire for the manufacture of pipe fabric is produced in accordance to ASTMand CSA specifications as listed in Table 1. You will note that plain and deformed welded wire reinforcementhave a minimum yield strength equal to 450MPa (65ksi) and 485 MPa (70ksi), respectively. Higher yieldstrengths, improved weldability, pre-manufactured quality control and fabricating efficiencies are the primaryadvantages of welded wire reinforcement.
ASTM A 82 CSA G 30.3 Steel Wire, Plain, For Concrete Reinforcement
ASTM A 185 CSA G 30.5 Steel Welded Wire Fabric, Plain, For Concrete Reinforcement
ASTM A 496 CSA G 30.14 Steel Wire, Deformed, For Concrete Reinforcement
ASTM A 497 CSA G 30.15 Steel Welded Wire Fabric, Deformed, For Concrete Reinforcement
Information Tables 2, 3 and 4
See Tables 2, 3 and 4 for load/force conversion factors, a common list of typical wire spacings converted tometric dimensions and a table on properties of wire for welded wire reinforcement for pipe fabric.
Table 2Length, Area, Mass and Load/Force Conversion Factors or Multipliers
From X To
inches 25.4 mm
feet 0.3048 meters
in 2 645 mm 2
in2/foot 2116.7 mm 2/meter
lbs/ft 2 4.882 kg/m 2
lbs 0.45359 kg
in2(area) 3.4 lbs/foot(weight)
lbs/ft(weight) 1.488 kg/m(mass)
mm2 (area) 0.007849 kg/m(mass)
lbs(force) 4.448 N(Newtons)
lbs/lin. feet (plf) 14.5931 N/m(Newtons/meter)
lbs/in 2 0.006897 MPa(mega Pascals)
Table 3Common Pipe Fabric Wire Spacings
Inches Actual Spacingmm*
Call-outSpacing
2 50.8 51
3 76.2 76
6 152.4 152
8 203.2 203
*When figuring weights (mass) use actual wire spacing dimension and actual wire sizes from Table 4.
Figure 3 Nomenclature
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
PIPE FABRICTable 4
Metric Wire Areas, Diameters & Mass With Equivalent Inch-Pound Units3
Metric Units1 Inch-Pound Units 2
Call-out Size4
(MW=Plain)(mm2)
Actual sizeor
Area(mm2)
Diameter(mm)
Mass(kg/m)
Actual Size4
Area(W=Plain)(in2x100)
Diameter(in)
Weight(lbs./ft.)
GageGuide
MW122
MW116
MW103
MW90
MW84
MW77
MW74
MW71
MW68
MW65
MW62
MW58
MW55
MW52
MW48
MW45
MW42
MW39
MW36
MW32
MW29
MW26
MW23
MW19
MW16
MW13
MW11
122
116
103
90.3
83.9
77.4
74.4
71.0
67.9
64.5
61.3
58.1
54.9
51.6
48.4
45.2
42.1
38.7
35.5
32.3
28.9
25.8
22.6
19.4
16.2
12.9
11.3
12.46
12.17
11.46
10.72
10.33
9.93
9.73
9.50
9.30
9.07
8.84
8.59
8.36
8.10
7.85
7.60
7.32
7.01
6.73
6.40
6.07
5.74
5.36
4.97
4.54
4.05
3.79
.958
.910
.809
.708
.658
.607
.583
.556
.533
.506
.481
.456
.430
.405
.379
.354
.329
.304
.278
.253
.228
.202
.177
.152
.126
.101
.089
W19
W18
W16
W14
W13
W12
W11.5
W11
W10.5
W10
W9.5
W9
W8.5
W8.0
W7.5
W7.0
W6.5
W6.0
W5.5
W5.0
W4.5
W4.0
W3.5
W3.0
W2.5
W2.0
W1.75
.491
.479
.451
.422
.407
.391
.383
.374
.366
.357
.348
.339
.329
.319
.309
.299
.288
.276
.265
.252
.239
.226
.211
.195
.178
.160
.149
.643
.612
.544
.476
.442
.408
.391
.374
.357
.340
.323
.306
.289
.272
.255
.238
.221
.204
.187
.170
.153
.136
.119
.102
.085
.068
.059
7/0
6/0
5/0
4/0
3/0
2/0
1/0
1
2
3
4
6
8
10
1Metric wire sizes can be specified in 1 mm 2 increments.2Inch-pound sizes can be specified in 0.001 in2 increments.3 -For other available wire sizes, consult other WRI publications or discuss with welded wire reinforcement manufacturers.4 -Wires may be deformed, use prefix MD or D.Note I -Pipe fabric is provided in rolls or coils, but may be made in sheets
Page 4 • TF 311-M-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
SECTIONAL AREAS OF WELDED WIRE FABRICMetric Units1
Call-out SizeMW=Plain4
Actual Size orArea3
NOMINALDIAMETER
NOMINALMASS
As - mm2 PER METER
mm 2 mm2 mm kg/m 51 76 102 152 203
MW122 122 12.46 0.958 2392 1605 1196 803 601
MW 116 116 12.16 0.910 2275 1526 1137 763 571
MW 103 103 11.46 0.809 2020 1355 1010 678 507
MW 90 90.3 10.72 0.708 1771 1188 885 594 445
MW 84 83.9 10.33 0.658 1645 1104 823 552 413
MW 77 77.4 9.93 0.607 1518 1018 759 509 381
MW 74 74.4 9.73 0.583 1459 979 729 489 366
MW 71 71.0 9.50 0.556 1392 934 696 467 350
MW 68 67.9 9.30 0.533 1331 893 666 447 334
MW 65 64.5 9.07 0.506 1265 849 632 424 318
MW 62 61.3 8.84 0.481 1202 807 601 403 302
MW 58 58.1 8.59 0.456 1139 764 570 382 286
MW 55 54.9 8.36 0.430 1076 722 538 361 270
MW 52 51.6 8.10 0.405 1012 679 506 339 254
MW 48 48.4 7.85 0.379 949 637 475 318 238
MW 45 45.2 7.60 0.354 886 595 443 297 223
MW 42 42.1 7.32 0.329 825 554 413 277 207
MW 39 38.7 7.01 0.304 759 509 379 255 191
MW 36 35.5 6.73 0.278 696 467 348 234 175
MW 32 32.3 6.40 0.253 633 425 317 213 159
MW 29 28.9 6.07 0.228 567 380 283 190 142
MW 26 25.8 5.74 0.202 506 339 253 170 127
MW 23 22.6 5.36 0.177 443 297 222 149 111
MW 19 19.4 4.97 0.152 380 255 190 128 96
MW 16 16.2 4.54 0.126 318 213 159 107 80
MW 13 12.9 4.05 0.101 253 170 126 85 64
MW 11 11.3 3.79 0.089 222 149 111 74 56
1Metric wire sizes can be specified in 1 mm 2 increments.2Inch-pound sizes can be specified in 0.001 in2 increments.3For other available wire sizes, consult other WRI publications or discuss with welded wire reinforcement manufacturers.4Wires may be deformed, use prefix MD.Note - Pipe fabric is provided in rolls or coils, but may be made in sheets.
Page 5 • TF 311-M-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
SECTIONAL AREAS OF WELDED WIRE REINFORCEMENTInch-pound Units2
ACTUAL WIRE SIZE3
OR AREA W = PLAIN4
NOMINALDIAMETER
NOMINALWEIGHT
As - SQ. IN PER LINEAR FT.CENTER TO CENTER SPACING
(in 2 x 100) in lbs./lin. ft. 2" 3" 4" 6" 8"
W19 0.491 0.643 1.13 0.76 0.57 0.38 0.28
W18 0.479 0.612 1.08 0.72 0.54 0.36 0.27
W16 0.451 0.544 0.96 0.64 0.48 0.32 0.24
W14 0.422 0.476 0.84 0.56 0.42 0.28 0.21
W13 0.407 0.442 0.78 0.52 0.39 0.26 0.195
W12 0.391 0.408 0.72 0.48 0.36 0.24 0.18
W11.5 0.383 0.391 0.69 0.46 0.345 0.23 0.173
W11 0.374 0.374 0.66 0.44 0.33 0.22 0.165
W10.5 0.366 0.357 0.63 0.42 0.315 0.21 0.157
W10 0.357 0.340 0.60 0.40 0.30 0.20 0.15
W9.5 0.348 0.323 0.57 0.38 0.285 0.19 0.142
W9 0.339 0.306 0.54 0.36 0.27 0.18 0.135
W8.5 0.329 0.289 0.51 0.34 0.255 0.17 0.127
W8 0.319 0.272 0.48 0.32 0.24 0.16 0.12
W7.5 0.309 0.255 0.45 0.30 0.225 0.15 0.113
W7 0.299 0.238 0.42 0.28 0.21 0.14 0.105
W6.5 0.288 0.221 0.39 0.26 0.195 0.13 0.098
W6 0.276 0.204 0.36 0.24 0.18 0.12 0.09
W5.5 0.265 0.187 0.33 0.22 0.165 0.11 0.083
W5 0.252 0.170 0.30 0.20 0.15 0.10 0.075
W4.5 0.239 0.153 0.27 0.18 0.135 0.09 0.068
W4 0.226 0.136 0.24 0.16 0.12 0.08 0.06
W3.5 0.211 0.119 0.21 0.14 0.105 0.07 0.053
W3 0.195 0.102 0.18 0.12 0.09 0.06 0.045
W2.5 0.178 0.085 0.15 0.10 0.075 0.05 0.038
W2 0.160 0.068 0.12 0.08 0.06 0.04 0.03
W1.75 0.149 0.059 0.105 0.07 0.053 0.035 0.026
1Metric wire sizes can be specified in 1 mm 2 increments.2Inch-pound sizes can be specified in 0.001 in2 increments.3For other available wire sizes, consult other WRI publications or discuss with welded wire reinforcement manufacturers.4Wires may be deformed, use prefix D.Note - Pipe fabric is provided in rolls or coils, but may be made in sheets.
Page 6 • TF 311-M-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
A Design, Construction & Inspection AidFor Consulting Engineers
March, 1996
Prepared for:
Copyright, Wire Reinforcement Institute
Wire Reinforcement Institute
942 Main Street
Hartford, CT 06103
Phone (800) 522-4WRI [4974]
Fax (860) 808-3009
Authored By:
Walter L. Snowden, P.E.
Austin, TX
512-338-0431 or 512-338-1804
This report is furnished as a guide to industry practice. The Wire Reinforcement Institute (WRI) and It’s members make no war-ranty of any kind regarding the use of this report for other than informational purposes. This report Is intended for the use ofprofessionals competent to evaluate the significance and the limitations of its content and who will accept the responsibility forthe application of the material it contains. WRI provides the following material as a matter of information and, therefore, dis-claims any and all responsibility jot application of the stated principles or the accuracy of the sources other than material devel-oped by the Institute.
Page 1 • TF 700-R-03Update
INTRODUCTIONIn 1981 “DESIGN OF SLAB-ON-GROUND FOUN-DATIONS, A Design, Construction & InspectionAid for Consulting Engineers” was first published.The design procedure set forth in that publicationhad at that time been in use by the author for about15 years. After this publication, it was subsequent-ly adopted by the Uniform Building Code (UBC) asStandard 29-4(I). Copies of this work have beendistributed by WRI for 22 years to consultants allacross the nation. Feedback has been most favor-able with no comments of design inadequacy. In afew cases there have been suggestions that thisprocedure produced extra conservative designs,but this guide is intended to always produce a safe,serviceable foundation. Engineers who care to arefree to exercise their judgement and to adjust theresults in either direction.
SOILS INVESTIGATIONSIt is still mandatory that soils investigation be madeon any site to set out the necessary conditions fordesign. The original recommendation of a mini-mum of one boring for each isolated site is stillvalid, but many insuring agencies have specified atleast two borings in areas where expansive clay isfound. Large sites and subdivisions will need aspecific planned program utilizing several borings.Subdivisions will usually average about one boringfor every 3 or 4 contiguous lots. Borings should bea minimum of 15 feet deep in most cases, and insome instances will need to be deeper. The soilsEngineer should be sure to obtain adequate infor-mation to cover any grading changes which can beanticipated. Fill should be identified and noted.Uncompacted fill placed on a site, and improperdrainage have been found to be the largest con-tributors to unsatisfactory foundation performance.Either one or both are guarantees of foundationproblems.
During the last 22 years, many alternatives to anadequate on-site investigation have been pro-posed; soils maps, adjacent data, guesses, andsomething called a “max design”. A “max design” is supposedly a design for the maximum soil condi-tion in the area. How is that known unless an on-
site investigation has been done? That is anothername for a guess.
What remains true is that the performance of theslab is influenced primarily by the underlying soil. Ifthe severity of the soil is underestimated, the foun-dation will not be satisfactory. It is therefore essen-tial to know what type soil conditions exist, and thatcan only be known through an adequate site inves-tigation.
LOADING CONDITIONSFor one, two, and even three story wood frameconstruction such as homes and small commercialbuildings, the assumption of uniform load workswell with the design equations. If there are largeconcentrated loads or numerous columns, atten-tion must be paid to the location of stiffeningbeams or thickened areas of the slab so that theload can be spread out. Buildings which are carriedtotally on columns need a different analysis from auniform loading assumption.
DESIGN ASSUMPTIONSThe design procedure presented originally by TheBuilding Research Advisory Board (B.R.A.B.) intheir Report 33, assumed a loss of support at theedges (Fig 1a) and a loss of support at the center(Fig 1b).
Edge Settlement
Figure 1
Figure 2
Center Settlement
Edge Heave
Center Heave
Page 2 • TF 700-R-03Update
These conditions approximated the conditions ofcenter heave or edge settlement and center settle-ment or edge heave as shown in Figure 2.
By making some simplifying assumptions it waspossible to analyze the foundation slab by applyingthe loading conditions in both the long and shortdirections (Figure 3).
GEOGRAPHIC CONSIDERATIONS
Figure 3
Climatic Ratings (Cw) for Continental United StatesFigure 4
BRAB utilized the Climatic rating (see Figure 4) of the locality to reflect the stability of the moisturecontent in an expansive soil. While there are other methods of accounting for the seasonal moisturechange potential, this system has seemed to work well.
← Non-supported
← Supported
← Non-supported
a. Cantilever
b. Simple Span Beam
Page 3 • TF 700-R-03Update
Looking at the various loading conditions above and slabs in the field, it became apparent that the foun-dations were very sensitive to the changes at the edges. It was decided that a cantilever distance, (Ic)
would be used as a basis for this design procedure to replace the L(1-C) utilized by BRAB. Figure 5 givesa cantilever design length for a given soil condition (PI) in a given climatic rating (Cw).
DESIGN LENGTH
Figure 5
Page 4 • TF 700-R-03Update
It seems apparent that the size of the foundationmust also be considered. The values given inFigure 5 for the cantilever length are for largeslabs. Figure 6 gives a modification coefficientwhich will adjust the cantilever length for smallerslabs depending on the slab size.
SOIL CONDITIONSThe design procedure shown in this report isbased on the use of the “effective P.I.” (PIo). It haslong been known that the Plasticity Index (PI) ofthe soil can be used as an indicator of the PotentialVolumetric Activity of a given soil. It has the addedadvantage of being a test which is familiar andinexpensive to perform.
Obviously, different soils have different Pls, and thePl may change with depth at any one location. Toaccount for this, the design procedure first calcu-lates an “equivalent” or “weighted” PI. It is neces-sary to use the weighing system shown in Figure 7to be compatible with this design procedure.
This weighing method gives more attention to theupper soils where the soil would have the opportu-nity for more activity, and reduces the activitypotential with depth due to confining pressure andprotection from seasonal moisture changes, etc.This is not the only way to weight this effect, but ithas proved to be very satisfactory, and must beused for this procedure.
There are instances where this weighing systemmight give unconservative results. One would bewhere the underlying formations might containsand stringers or are overlaid by porous sandwhich would provide quick, easy routes for water toreach any underlying or interbedded expansiveclays.
A second case would be where highly expansiveclays overlaid a rock formation. Using a zero (0) PI.for these rock layers can reduce the equivalent P.I.excessively, making it appear to be a very stablesite. It is recommended that to eliminate this prob-lem, a minimum P.I. of 15 be used for any layerswhich have little or no P.I.
OTHER PARAMETERS OF CONCERNOther factors to be considered are slope anddegree of consolidation. Figures 8 and 9 presentmodification coefficients to be used with the “equiv-alent” PI to obtain the “effective” PI.
Figure 7
Figure 6
Figure 8
Slope of natural ground vs. Slope Correction Coefficient
The effective PI then is:PIo=equivalent PI x C5 x Co
Where:C5 is the slope correction coefficientCo is the consolidation correction coefficient
As an example: assume -Equivalent (or weighted) PI = 3010% ground slope C5 (Fig. 8) = 1.1 6 TSF Unconfined Co (Fig. 9) = 1.2PIo = 30 x 1.1 x 1.2 = 39.6
Use an Effective Plasticity Index of 40 for designpurposes
HOUSE GEOMETRY AND LOADSIt is best to calculate the total weight of house andfoundation, but in lieu of that, or as a starting pointit is possible to use the following for most conven-tional wood frame houses with no unusual fea-tures (tile roofs, floors, high masonry loads, etc).
1 story - 200 lb/sq.ft.2 story - 275 lbs/sq.ft.3 story - 350 lbs/sq.ft.
Most houses can be subdivided into several rec-tangles and each section then be analyzed andthen overlaid as shown in Figure 10.
To begin the analysis the number of beams mustbe determined. Sometimes the geometry of thehouse will dictate the number of beams (N)required, sometimes the following equation will beused.
L' Where: S = Spacing ft (m) from Fig. 5N = S +1 L' = width of slab, ft (m)
Once N is known, a very good first approximation ofthe depth of the beams can be determined by theequation:Using these equations yields a starting point with Nnumber of beams, b inches wide and d inches deepwhich will give a Moment of Inertia (Iin4) adequateto limit deflection to the order of magnitude of1/480. This deflection ratio is greater than the usual1/360, but it usually furnishes beam depths whichallow the reinforcing requirement to be two or threebars of moderate size top and bottom. Of course, ifthe reinforcing requirement is still extremely large,try deepening all or some of the beams to lessenthe reinforcing required.
In calculating the actual I of the slab, the sectionsshown in Figure 11 should be used. As can beseen, the exterior beams can be deepened, or allbeams can be deepened. It is felt that deeper exte-rior beams are more effective, but as long as theslab is kept symmetrical it does not seem to matter.
Page 5 • TF 700-R-03Update
Figure 10
Slab 1
Combined SlabsSlab 2
Where:d = Beam depth, in (mm) B = Sum of all widths, in (mm)M = Moment, kip-ft (N-m)lC = Cantilever length, ft (m)
3664 MlC
Bd =
Figure 11
d
b b b
t
f(t) f(t) f(t) f(t)
Effective Width of “T” Beams
SlabSegments
Figure 9Unconfined Compressive Strength vs. Consolidation Correction Coefficient
Unconfined Compressive Strength (qu) TSF
Page 6 • TF 700-R-03Update
DESIGN CALCULATIONS
Now that the conditions have been defined, thefollowing formulas can be used to calculate themoment, deflection and shear.
Naturally, these calculations will be performed inboth the long and short directions.
TEMPERATURE AND SHRINKAGE REIN-FORCEMENT FOR CRACK CONTROLThe greatest number or reported complaintscomes in the form of "cracked slabs". Of course allconcrete will crack. Shrinkage crack preventionhas spawned a plethora of papers, documents andbooks. The engineering community understandsshrinkage cracking for the most part, but the gen-eral public sees each crack as a "structural failure".It is therefore very important to properly addressthe subject of minimum reinforcing to minimizeshrinkage cracking and control crack widths.
The amount of reinforcing needed to control crackformation and width has been found to increasewith the expansive potential of the site. Over theyears greater need has developed to provide crackcontrol to alleviate homeowners worries. When the
beam spacings are near those shown in Figure 5,the minimum reinforcing shown also in Figure 5 isusually adequate. While this will not prevent shrink-age cracking, it will provide adequate reinforcing tohold cracks to a minimum width during deflection.In the field, actual deflection is a function of theexpansive nature of the soil, and the stiffness ofthe slab, so the soil and the beam spacing togeth-er influence the deflection. Since the beam spacingis based on the soil (PI) and climate (Cw), the min-imum slab reinforcement can also be based on thesame factors.
HIGH STRENGTH WELDED WIRE REINFORCEMENT
The use of welded wire reinforcement in concretehas a long history. For this procedure it is stronglyrecommended that sheets of welded wire, plain ordeformed be used. This will provide positive place-ment in the slab. Welded wire reinforcement sheetscan be placed with the same degree of accuracyas tied reinforcing bars. Sheets with larger wiresand wider spacing are more readily available, andare easily positioned. The use of high strengthwelded wire has been accepted by code and somereal economies can now be realized, not only inmaterial costs, but in placement costs.
Use of WWR actually provides the engineer a largenumber of choices as can be seen by the compar-ison below. Assuming a moderate soil conditionand climatic conditions noted, the reinforcing inChart 1 would be acceptable.
On higher PI soils, it would seem advisable to go toheavier slab reinforcing, even though the stiffnessof the slab should be such that cracks would nottend to open any more than at lower PIs. To seehow that would look for a higher PI soil, compareChart 1 to Chart 2.
M =wL’ (lc)2
2
∆=w (lc)4 L’
4EcI
V= wL’ lc
Where: M = Moment + or -, kip-ft (N.m)
∆ = Deflection, in (mm)
V = Total shear, lbs (kg)
w = Unit weight, psf (kg/m2)
L’ = Width of slab, ft (m)
1c = Cantilever, (lc k) ft (m)
Ec = Creep Modulus of Elasticityof concrete, psi (MPa)
I = Moment of Inertia, in4 (mm4)
Page 7 • TF 700-R-03Update
These values will approximate requirements of ACI318, which allows for designs with yield strengthup to 80,000 psi.
Use of the higher yield strengths will result in sav-ings due to steel weight. Further savings can berealized by utilizing small edge wires closelyspaced as shown in Figure 12. Savings will varywith specific areas, but some studies have shownthat for each 5000 psi increase in fy, about 8% insteel weight is reduced. The use of small edgewires closely spaced can save an additional 3% ormore. Perhaps the greatest saving will be in plac-ing where costs have been reported to be reduced50% and more over other conventional steel rein-forcing.
A DESIGN EXAMPLEThis design example utilizes welded wire reinforce-ment for slab-on-ground foundations over soilswith high PI values:Given: PI = 60
Cw=18 A8fy = 5200 lbs (fy = 75,000psi)
Slab Thickness = 4"
Then: A8 = 0.0018 x 60,000 x (4 x12) = 0.069 in.2/ft of concrete cross section75,000
Check strength level required: A8fy = 75.000 x 0.069 = 5175 = 5200 OK
CONCLUSIONSThis design procedure, which has been in useabout 37 years at this time, has produced satisfac-tory foundations for single family housing andsmall commercial applications. This update ismeant to make it easier for the consultant to use bycombining several tables into one (Fig 5). TheEffective Pl, and the Climatic Rating are all thatneed be known to obtain a cantilever length fordesign.
This paper is a condensation of more detailedwork. Engineers may obtain copies of the originalwork by contacting the WRI. Copyright, WireReinforcement Institute Wire ReinforcementInstitute 942 Main Street, Suite 300, Hartford,CT 06103 Phone: 800 522-4WRI(4974) • Fax:860 808-3009 THE AUTHOR Walter L. Snowden,P.E. Austin, TX, 512-338-0431 or 512-338-1804
COMPARISON OF REINFORCING (1)Pl=60 Cw = 18 A8fy = 3833
Yield Stress Size Spacing** Stylefy A8 (W -D)
COMPARISON OF REINFORCING (2)Pl=60 Cw = 18 A8fy = 5200
Yield Stress Size* Spacing** Stylefy A8 (W-D)
60000 .086 W8.6 12"O.C. 12x12-W8.6xW8.6
65000 .080 W8.0 12"O.C. 12x12-W8.0xW8.0
70000 .074 W7.4 12"O.C. 12x12-W7.4xW7.4
75000 .069 W6.9 12"O.C. 12x12-W69xW6.9
80000 .065 W6.5 12"O.C. 12x12-W6.5xW6.5
60000 .064 W6.4 12"O.C. 12x12-W6.4xW6.4
65000 .059 W5.9 12"O.C. 12x12-W5.9xW5.9
70000 .055 W5.5 12"O.C. 12x12-W5.5xW5.5
75000 .051 W5.1 12"O.C. 12x12-W5.1xW5.1
80000 .048 W4.8 12"O.C. 12x12-W4.8xW4.8
* W = plain wire, also can be prefix D for deformed wire.** Wire spacings are available in 2” to 18” in either or both longitudinal and traverse directions. Contact individual welded wire
producers for specific styles and spacings of WWR
Chart 1 Chart 2
Figure 12
Full sized wire
Full sized wire
Side Lap DetailTransverse wires
Half-sized wires@ half spacing
Lap
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
TF 702-R-03
Low Maintenance SlabsSupports Are Needed for Long-Term Performanceof Welded Wire Reinforcement In Slabs-On-GradeINTRODUCTION
Tying WWR is very quick and easy — simply tie at overlaps and afew ties may be required at supports.
The design of slabs-on-grade is less straightforwardand less restricted by building codes than is the casefor supported slabs. While these less prescriptiverequirements have led to a variety of practices in thefield, it has also allowed significant innovations bydesigners and constructors of slabs-on-grade.Whatever the case, however, reinforcement must beproperly detailed on the project drawings, and then beaccurately located and securely tied before and duringconcrete placement. It may be necessary with lightWWR styles to place supports and properly positionreinforcement as the concrete is being screeded. Withheavier styles or wide wire spacings the supportscould be placed before concrete placement. Thesesteps are absolutely necessary for the reinforcementto perform its intended function.
When WWR (deformed or plain wire) is specified, thecombination of wire diameters and wire spacingsshould be selected to maintain the WWR’s properposition during the construction process. Moreover,WWR always should be supported as described in thisreport.
DESCRIPTION OF A SLAB-ON-GRADEA number of phrases are used to describe a slab-on-grade, including a grade slab, a floating slab and,simply, a slab. The key point is that such a concrete slab
Welded wire reinforcement placed on welded wire supports.
With its cost-efficiency and superior performanceattributes, welded wire reinforcement (WWR) fre-quently is the reinforcing steel of choice for slabs-on-grade. However, WWR’s full benefits in controllingcracking and reducing maintenance can only be real-ized when it is accurately positioned with properlyinstalled supports.
One of the primary causes for an under-performingslab-on-grade is the inadequate positioning or com-plete absence of supports. Yet, there is no justificationfor improper placement or inadequate support ofWWR, particularly since the process is relatively easyand inexpensive to accomplish.
This report, which is directed largely to architects,engineers and contractors, encourages the use ofproper supports for WWR in slabs-on-grade, includingindustrial floors, light commercial floors, residentialfloors, parking lots, sidewalks and, in general, allconcrete flat work. It supplements the WireReinforcement Institute’s Tech Fact 705, InnovativeWays to Reinforce Slabs-On-Ground.
WWR is used primarily to control cracking due toshrinkage, thermal stresses and other effects, andthus reduces future maintenance while helping to pro-duce a higher quality slab. However, WWR also maybe designed and used as structural reinforcement forthe slab.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 2 • TF 702-R-03
Welded wire reinforcement for highway paving and whitetoppingis being specified more today— properly supported WWR helpsprotect against damaging transverse and longitudinal cracking.
has continuous contact support with a prepared baseor subgrade material. The report by ACI Committee360 defines a slab-on-grade as a slab which iscontinuously supported by “ground,” may be ofuniform or variable thickness, and may also havestiffening elements such as ribs or grade beams.
WHY SUPPORTS FOR REINFORCEMENTARE NECESSARYThe primary performance requirement for supports ofwelded wire is that the supports hold the reinforce-ment in the proper vertical position within the slabduring placement of the concrete. Properly positionedwelded wire will reduce future maintenance costs forthe slab.
It is not recommended that reinforcement beplaced on the grade surface and then pulled up (so-called “hooking”), nor is it recommended that the rein-forcement be placed on the freshly placed concreteand depressed into the concrete (so-called “walking-in”). Both of these practices are no longer usedbecause the resulting location of the reinforcing steelis approximate and can not be inspected for actualplacement. Project specifications should indicate therequirements for properly supporting the reinforcement.
Various types of supports for WWR are commer-cially available. The types of supports include wireand welded wire supports, individual high chairswith plates, bolsters with plates, all-plastic supports,concrete blocks, and others. Individual high chairsor bolsters without plates may be used with a firmsub-base or mud mat. See Figure 1 for some exam-ples of supports.
Wide spaced wires and wide support spacings are cost effectivewhile maintaining proper positioning of reinforcement.
POSITION OF REINFORCEMENT AND COVERThe proper position for the steel reinforcement is adecision based on the design itself and is controlledby the intended function of the steel. When one layerof reinforcement isused, then it should be located ator above the mid-depth of the slab. Some archi-tects/engineers require that the single layer be placed2 inches below the top surface of the slab. In thickerslabs, the reinforcement must be low enough so thatit will not interfere with saw cutting. Others recom-mend that the layer be placed at one-third the depthbelow the top surface. Any of these locations can bethe appropriate choice, depending on the design con-cept — for example, whether the slab is reinforced forcrack control, or is reinforced for structural reasons,or designed for shrinkage-compensating concrete.When one layer of reinforcement is used, it shouldnot be allowed to be below mid-depth. In general,positioning at one-third the depth below the surfaceis sufficient.
Here concrete blocks support the bottom layer of WWR andcontinuous wire chairs support the top layer.
When two layers of reinforcement are used, the ques-tion of cover applies to both layers. The upper layershould beplaced at least 1 inch below the top surfaceof the slab. However, it should not be positioned tooclose to the top surface due to the variation in flatnesscreated when that surface is finished. The specifieddepth of any saw cut must also be considered and theupper layer placed below that saw cut. In the case of
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 3 • TF 702-R-03
The supports selected must properly position the welded wirereinforcement and provide adequate support until the concretecures.
Two-course slab construction is occasionally used inairport and paving work where the slab is thicker thannormally encountered in industrial plants, commercialbuildings, and residential buildings. The WWR isplaced on the first course of low slump concrete andthe remainder of the concrete is then placed. Thistwo-course technique is not common in building con-struction; when it is used the resultant position of thereinforcing steel may not be as accurate as whensupports are used.
WWR is placed on the first course of low slump concrete in thisairport taxiway.
INFLUENCE OF BASE CONDITIONS ONSELECTION OF SUPPORTSThe condition of the upper portion and top surface ofthe subgrade is crucial to the proper selection of thesupport system. For example, soft base materials,such as loose sand, require supports with base platesor with appreciable contact areas. Stiffer and morestable base materials, such as a compacted granularbase, should allow the use of wire and plastic sup-ports without base plates or concrete blocks. Inselecting the supports it is necessary to consider boththe reinforcement to be supported and the basedirectly under the supports. Most manufacturer’sbrochures will indicate the base surfaces required fortheir products.
The ACI Committee 360 report recommends agraded granular fill, appropriate for compaction andtrimming, as the base material for slabs-on-grade.Gravel bases, when compacted, fit this description.Compacted granular fill allows a greater variety ofsupports for consideration due to the inherentstrength and stability of gravel. The so-called sandcushion (a few inches of uniformly graded sand) isusually not stable or stiff, and thus demands the use ofsupports with base plates or concrete blocks. Thesupports must not penetrate the base (subgrade) dur-ing the construction process because the specifiedposition of the reinforcing steel could be changed andits beneficial effect diminished. When polyethylenesheeting is used under a slab the selected supportsmust not puncture the sheeting. Other materials may
the lower layer, when the concrete slab is placed ona well-constructed base course (normally graded,compacted and porous), many who design floorsconsider 11/2˝ of clear cover below the steel to beadequate. Additional cover should not be necessaryunless the governing building code requires a bottomcover of up to 3 inches.
Highway reinforcement supported on continuous wire chairs.
TYPES OF SUPPORTSAlthough this report concentrates on slabs-on-grade,supports are also used for foundation mats andsupported slabs. Some are shown in Figure 1 butthese and others are well described in support manu-facturer’s brochures.
For a particular project, the supports should beselected taking into account the size and weight ofthe welded wire reinforcement, the stiffness andstrength of the base or subgrade, the specified posi-tion of the reinforcing steel including the number oflayers, and the construction process to be used forplacement of the concrete. The supports selectedmust properly position the reinforcing steel so itremains in place during the construction process anduntil the concrete hardens. Supports must be com-patible with the concrete and be positioned firmly onthe top of the base surface or subgrade. It is not nec-essary to stagger supports. Generally, vibration of theconcrete is specified to obtain adequate consolidationof the concrete materials and would be sufficient toencase the supports, thus preventing voids.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 4 • TF 702-R-03
be required under a slab due to special circum-stancesor conditions. For example, the floors incold storage or freezer warehouses are usuallyplaced upon insulation boards. The selectedsupports must not penetrate the insulation board.
SPACINGS AND STRENGTH OF SUPPORTSAfter having determined the amount of reinforce-ment required, the next step is to determineits correct position within the slab. To accomplishthe purpose of the reinforcement it is essentialthat it be placed on supports and these require-ments should be stated in the project specifica-tions. Many types and configurations of supports,as well as devices for special purposes not dis-cussed in this report, are commercially available.
wire reinforcement. There are several factors toconsider before determining support spacings.These factors include the diameter and spacingof the reinforcement (larger wire diameters withwider support spacings will allow workers to stepthrough rather than on the reinforcement); andgeneral recognition of any construction loadsthat will be applied before and during concreteplacement. The welded intersections of WWRprovide a very rigid sheet of reinforcement.
Properly positioned steel below the saw cut control jointallows concrete to crack the full depth and adds loadtransfer capacity across the joint.
Examples of some types of supports are shownin Figure 1. Generally these supports arespaced 2 to 6 (or more) feet apart, depending onthe stiffness and weight of the WWR beingsupported. Between the supports, the reinforce-ment must not deflect or sag excessively. Whilethere are no criteria for limiting this deflection,the reinforcement must not deflect beyond anyrequired clearances.
There is limited information available onrequirements for support spacings for welded
A variety of wire and plastic supports are available — manyare made especially for welded wire reinforcement.Adequate spacing of supports depends on the style and sizeof wires. Spacings of supports varies from 2 - 6 feet andmore depending on wire sizes and spacings.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 5 • TF 702-R-03
This report is furnished as a guide to industry practice. TheWire Reinforcement Institute (WRI) and its members make nowarranty of any kind regarding the use of this report for otherthan informational purposes. This report is intended for the useof professionals competent to evaluate the significance andlimitations of its contents and who will accept the responsibilityfor the application of the material it contains. WRI provides theforegoing material as a matter of information and, therefore, dis-claims any and all responsibility for application of the stated prin-ciples or the accuracy of the sources other than material devel-oped by the Institute.
The suggested spacings of supports in Table 1 may be used for estimating and construction. However, thepreceding factors should be considered.
TABLE 1. SUGGESTED SPACINGS OF SUPPORTS
Welded Wire Reinforcement Range Welded Wire Spacing Suggested Support Spacing
W or D 9 or larger* 12” and greater 4-6 ft.W or D5 to W or D8 12” and greater 3-4 ft.W or D9 and larger Less than 12” 3-4 ft.W or D4 to W or D8 Less than 12” 2-3 ft.Less than W or D4** Less than 12” 2-3 ft. or Less
*Spacing of supports for WWR with wires larger than W or D9 could possibly be increased over the spac-ings shown depending on the construction loads applied.
**Consider using additional rows of supports when large deflections or deformations occur — also spacing ofsupports may be increased provided supports are placed and properly positioned as concrete is screeded.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 6 • TF 702-R-03
As ready mix trucks leave after tailgating the concrete in strippours, supports are placed to stay ahead of the laser screed onthis project . . .
For welded wire reinforcing sheets, spacings of theindividual wires should be a consideration to avoidpermanent displacement due to workers walking onthe reinforcement. This spacing should be 12 inchesor more (up to 18 inches may be specified). If thedesign requirements do not allow larger spacings,then the wire stiffness and the support strength andspacings must be adequate to carry all anticipatedconstruction loads.
The strength of the supports and their spacingsrequired to carry construction loads, other equipmentand workers must also be considered. There are noexact guidelines, but the requirement for strengthand stability cannot be ignored.
The applicability of the suggested spacings inTable 1 may best be confirmed by conducting on-sitetesting of the proposed arrangement of supports.Loadings caused by personnel and equipment canbe checked with minimum expense before proceed-ing with construction of the slab.
More cost-effectiveness and ease in placing can be achievedwith step-through styles of WWR (12x12 and larger).
Pumping concrete is a sure way to maintain properposition of supported reinforcement.
. . . Iaser screed rides easily over supported welded wire withoutexcessive displacement or distortion.
REFERENCES1. Innovative Ways to Reinforce Slabs-On-
Ground, Wire Reinforcement Institute Tech FactTF 705, 1996.
2. Design of Slabs On Ground (ACI 360R-92),American Concrete Institute, 1992.
3. Manual of Standard Practice, 5th Edition, Wire Reinforcement Institute, 1999.
4. Structural Detailing Manual, Wire Reinforcement Institute, updated 1994.
5. How to Specify, Order and Use Welded Wire in Light Construction, Tech Fact TF 202, Wire Reinforcement Institute, 1991.
6. Guide for Concrete Floor and Slab Construction(ACI 302.1R-96), American Concrete Institute, 1996.
7. Designing Floor Slabs on Grade, the Aberdeen Group, 1992, Authors - Boyd C. Ringo and Robert B. Anderson.
8. Kohl’s Tech Fact, TF 294 Wire Reinforcement Institute, 1994.
Based on a contribution by Boyd C. Ringo, P.E.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
ANSI/ASCE 9-91 Constructionof Composite Slabs Approves . . YES NO
Call or write us about projects that prove performanceand efficiency with WELDED WIRE REINFORCEMENT.
* Approves use but not replacement for conventional reinforcementment
TF 703
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Delayed Ettringite Formations and Alkali-Silica Formations WillFocus More Attention on Steel Reinforced Concrete DesignsWelded Wire Reinforced concrete is most important today and should be given serious considera-tion for all concrete construction. Since WWR products have a history of reducing cracking, crackwidths and displacement at cracks due to plastic shrinkage, drying shrinkage, thermal expansion andcontraction — and now the more recent findings of delayed ettringite formations or DEF, which causeexpansion and cracking around aggregates and the more typical alkali-silica reaction or gel formationscausing cracking through aggregates, Welded Wire Reinforced concrete should be specified morethan ever before.
If you want to reduce maintenance costs due to excessive cracking, wide cracks and displacement atcracks,Welded Wire Reinforcing is the answer.
Remember, even quality mix designs with various admixtures or enhancers do not ensure crack control. There are too manyvariables which cause cracking; therefore be safe and build in more crack control and the added reserve strength by order-ing Welded Wire Reinforcing on your next project.
Without Welded Wire Reinforcement, cracks can be verywide and could cause excessive maintenance costs.
. . . and if settlement occurs in the sub base displacementcan occur.
When Welded Wire Reinforcement is specifiedand used for concrete reinforcement, widecracks and displacement are reduced and cor-ner cracking due to curling is minimized.Remember, Welded Wire Reinforced concreteoffers a contingency benefit— it adds reservestrength to assist in supporting loads placed onthe concrete.
Unreinforced Paving vs. Reinforced PavingHere is a highway paving research project doneby the Iowa Department of Transportation. The41/2-inch secondary road was 37 years old whenthe last report was filed — notice the upper por-tion with visible cracking and displacement. Thatportion has no Welded Wire Reinforcement in it.
The paving section in the bottom portion of thephotograph has Welded Wire Reinforcement init— for reference the WWR style is a single layerof 6 x 6 - W2.9 x W2.9. Notice there are a fewhairline cracks but they are held tightly closedand no displacement is apparent.
Page 2 • TF 703-R-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
HIGH-STRENGTH WELDED WIREREINFORCEMENT (WWR)COMPARED WITH REBARWWR Saves Money Over RebarTypically, A Savings in Placing Costs of Over 50%Can Be Realized on the Average Project WhenWelded Wire Reinforcing is Used Over Rebar
Placing costs for welded wire reinforcement in lighterstyles, less than a W or D6, generally will be in the range of5 to 8¢ per square foot. Placing costs for heavier WWRstyles will be in the range of 9 to 15¢ per square foot.Compare those costs with rebar tying and placing costsand you will find welded wire will usually save you over 50%of your placing costs.
High-Strength WWR Will Save Up to 25% of the Weight ofReinforcing Materials While Maintaining the Same StrengthAs Conventional Reinforcing
" With welded wire you don't have to prepare it —i t is already weldedtogether — you pick it up and set it in place and continue the pour''
- Dave Smith, Project Manager,Murphy & Sons,General Contractor
Here is an example of a recent project: A 6” (152 mm) slab on ground1,2 requiring an area of steelin a single layer to be 0.094 in.2/ft. (200 mm2/m} requires the following steel reinforcing:
Both welded wire solutions saves approximately 20% of the weight over rebar3 [up to 80,000 psi (550MPa) yield strength WWR can save up to 25%]. In most cases the weight savings will result in an overallsavings of material delivered over rebar4 since it is necessary to consider the cost of tying rebar in placeor in mats. Further, the cost to handle the rebar is more labor intensive and that added cost must also befactored into the cost comparisons. Incidentally, support costs for WWR are the same costs used forrebar.
Overall, when you design and specify high strength welded wire reinforcement, the bottom linematerial in-place savings of up to 25% can be achieved over rebar. In many cases #3, #4 and #5rebar will only be available in Grade 60 material.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
‘’ You’re going to save a substantial amount in labor costs when you place welded wire. Compare that cost with having to prepare another productsuch as rebar . . . where you have to tie it and place it’’ — Dave Smith, Project Manager, Murphy & Sons, General Contractor.
Here Are Some Quotes from a General Contractor forProof of Cost Savings with WWROn a recent project,4 Dave Smith of Murphy & Sons,Southaven, MS said when asked—Why he used weldedwire instead of rebar?:
“ With welded wire reinforcing, you’ve got less manhours.You can take a sheet of welded wire and move it –typically 1 person can move it – it’s easier with 2 for placement procedures. When you’re dealing with rebar mats, it takes a minimum of 8 people to move it – that’s 8 people you’ve got to take from another part of the job to do that.”
On another question asked of Dave Smith—Will youcomment on the cost savings of reinforcing for yourrecent project?
“ As we all know from an owner’s standpoint and I representthe owner—costs are always a big factor. When it comesdown to the quality with a different product (welded wirereinforcement) and it costs less – it doesn’t get any betterthan that. That’s what we all try to achieve. You’re going tosave a substantial amount in your labor costs when youplace welded wire. Compare that cost with having to pre-pare another product like rebar – where you have to tie it andplace . . . where with welded wire you don’t have to prepareit. You pick it up and set it in place and continue the pour.”
ACI 318 Approves High StrengthWelded Wire ReinforcementThe ACI 318 Building Code has for a long time recognized thetwo materials, welded wire and rebar, as equal. Both WWRand/or rebar are used almost exclusively in reinforced concretesupported structures and precast/prestressed components.
For many years, previous ACI Code cycles have allowed wire,welded wire and rebar yield strengths to 80,000 psi for flexuralstresses5 Now, in addition the latest Code cycle, ACI 318-95approves deformed welded wire to 80,000 psi (550 MPa) inshear as well as flexure6,7
Some Other Facts About ConcreteReinforcementThe various concrete reinforcing steels, cold-worked wire forwelded wire reinforcement and rebar are very similar in appli-cation. Many times welded wire is used in combination withrebar to help keep a project on schedule or to provide therequired cross-sectional area of steel utilizing the most effi-cient and more readily available sizes of materials. It’s inter-esting to note that hot-rolled rod used as raw material for cold-worked wire and welded wire has very different metallurgicalproperties compared to rebar, but the physical properties arevery similar. It is well known when steel is coldworked thestrength is increased8 It is inherent with wire and welded wirethat cold-working low-carbon rod significantly increases theyield strength. Using high-strength welded wire reinforce-ment, allows engineers to specify lighter reinforcing while hav-ing the same or greater strength as rebar for more efficientand cost-savings designs. Remember, #3, #4 and #5 rebarsusually are only available in Grade 60.
References:1) WRI TF•705, “Innovative Ways to Reinforce Slabs on Ground” Robert Anderson, 19962) Designing Floor Slabs on Grade, Boyd Ringo and Robert Anderson, 1992, 19963) WRI Structural WWF Detailing Binder, 10 Chapters, Section 2 has tables comparing areas and weights of rebar and WWR with various strengths4) Video, “A Visit to a Distribution Center Construction Site, A Contractor’s Views”, 19955) WRI “Manual of Standard Practice”, WWF 500, 19926) Tests to Determine Performance of Deformed Welded Wire Fabric Stirrups, ACI Structural Journal, 91-S22, Griezic, Cook & Mitchell7) Evaluation of Joint-Shear Provisions for Interior Beam-Column-Slab Connections using High-Strength Materials, ACI Structural Journal, 89-S10, Guimaraes, Kreger, Jirsa8) Ductility of Wire Reinforcing - Industry Evaluation of WWR Elongation and Reduction of Area, 1992
Page 2 • TF 704-R-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in Concrete
WIRE REINFORCEMENT INSTITUTE®
TF 705-R-03
Formulas for SuccessInnovative Ways to Reinforce Slabs-On-GroundBACKGROUNDWith nearly a century of experience in designingslabs-on-ground, both with and without welded wirereinforcement (WWR), there is little question that thereinforced slabs provide superior performance overthose that are not reinforced. Rather, the question is,“What constitutes adequate reinforcement?”
Since inadequately reinforced slabs-on-ground willperform little better than those that are not reinforced,properly specified and placed WWR is key to thesuccess of the final product. The following explana-tions and formulas are supplied to the design profes-sional to clarify the function of reinforcing steel and toprovide a guide for selecting the proper procedure.
In elevated concrete structures, the purpose ofreinforcement is fairly well understood as beingnecessary to control positive and negative momentand to control shear. Since concrete has little tensilestrength, all tensile components are expected to beserviced by the tensile capacity of the reinforcing inthese elevated structures.
In slab-on-ground design, slab thickness is a functionof the modulus of rupture of the concrete. This bringsus to the evident conclusion that the concrete is notsupposed to crack. Since the normal role of steel rein-forcement hinges on the fact that the concrete mustcrack for the steel to perform, the designer is facedwith a paradox. It is therefore necessary to define boththe purpose of reinforcing slabs-on-ground and howthis is effectively accomplished.
There are three primary purposes for reinforcingslabs-on-ground and they are as follows:
1. Shrinkage Control2. Temperature Control3. Moment Capacity
Some may consider increased joint spacing as a purpose,but this is simply an extension of shrinkage control.
The suggested range of maximum joint spacings forconcrete floors on ground is determined relative toslab thickness. The author believes reinforcementdesigned by subgrade drag theory should be limited toslabs with joints in this range.
PURPOSE OF REINFORCEMENT
Figure 1
WWR sheets retain their flatness and do not deflect when placed onappropriately spaced supports, even during concrete placement.
Source "What Every Floor Designer Should Know About Concrete" Concrete Construction,February 1981.
The suggested range of maximum joint spacings for concretefloors on ground is determined relative to slab thickness. Theauthor believes reinforcement designed by subgrade drag theoryshould be limited to slabs with joints in this range.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 2 • TF 705-R-03
SHRINKAGE CONTROL STEEL AREA DESIGN PROCEDURESSingularly, shrinkage control is the greatest concern inthe design of slabs-on-ground. WWR along with jointspacing offer the two primary elements that can beeffective in controlling shrinkage cracks. Figure 1 indi-cates graphically the ratio of slab thickness to jointspacing for effective shrinkage control. The cross-hatched area indicates the range where welded wirein conjunction with joint spacing should be used tocontrol shrinkage. Undersizing the amount of weldedwire needed for this purpose is all too often common-place. Optimum control of shrinkage and thereby pro-viding microcracking (or aggregate interlock) takesover 1% steel area, a value seldom used.
Since concrete is brittle, it is all too susceptible toadditional fracturing due to a change in temperature.This change in temperature is commonly referred to asa temperature gradient. Welded wire reinforcingassists in a two-fold manner in resisting stressescaused by a change in temperature. First, the lawsof nature have been favorable in permitting bothconcrete and steel to have essentially the same coef-ficient of thermal expansion. This is a value ofapproximately 6.5 X 10-6 in/in/°F. Second, weldedwire is ductile, thereby modifying the thermal shockexperienced by the concrete. This permits thedesigner to calculate a distinct area of steel for aquantifiable thermal gradient.
Slab-on-ground design procedures usually providethe designer with a slab thickness. This thickness isgenerally a function of loading, subgrade modulus,modulus of rupture of the concrete, and slab stiffness.Since thickness and stiffness are interrelated, an iter-ative-process or the use of nomographs are common-place in thickness determination. Once this is deter-mined, the slab moment capacity can be determinedas simply the modulus of rupture of the concretemultiplied by the section modulus of a given section.If the designer wishes to provide this capacity with asufficient amount of welded wire reinforcing, onceagain an area of steel can be calculated. When theconcrete cracks to permit the steel to function, the sec-tion becomes more flexible. This changes the problemin a small degree. Thus a lesser area of steel would benecessary. This is reflected in the confirmed capacitydesign procedure.
There are essentially three purposes in reinforcingslabs-on-ground. These consist of shrinkage control,temperature control, and addressing moment capacity.Ostensibly, the greatest desire for the designer is toaddress shrinkage, or control shrinkage. The use ofwelded wire provides a means of controlling thewidth of shrinkage cracks even with relatively smallpercentages of steel. This type of minimal control canbe realized with the subgrade drag formula. Thesubgrade drag formula, although actively used by thedesign profession for many years, is recognized asoffering only modest shrinkage control and littleadded strength. Other procedures are available to thedesigner. These alternatives are now presented anddiscussed along with the subgrade drag procedure.The steel area calculation procedures discussed areas follows:
In the past, the concrete industry has suggestedthe use of the subgrade drag theory for slabs. The pro-cedure was developed primarily for a low ratio of steel,usually less than 0.1% and utilized so-called standardstyles of WWR (4x4 and 6x6 spacing with wire sizesfrom W1.4 to W4). Also, the procedure considerscontrol joint spacings of less than 25’. If longer stripsare placed, intermediate cracking may develop. It isstill used successfully today primarily for thin slabs,less than 6”, in residential and light commercial con-struction. The welded wire will control shrinkage crackwidth and help maintain aggregate interlock in slabthicknesses up to 5” with light superimposed loads, butother procedures should be considered when weldedwire is used for greater joint spacings, and greater slabthicknesses and greater superimposed loads. Thesubgrade drag equation is as follows:
As = FLW
where
As = cross-sectional area in square inches of steel per lineal foot of slab width
fs = allowable stress in reinforcement, psi, use 0.75fy
TEMPERATURE CONTROL
MOMENT CAPACITY
2fs
SUBGRADE DRAG PROCEDURE
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 3 • TF 705-R-03
F = the friction factor, use a range of 1.5 - 2, use 2
L = distance in feet between joints(the distance between the free ends of the slabthat can move due to shrinkage contraction or thermal expansion)
W = dead weight of the slab, psf, usually assumedto be 12.5 psf per inch of thickness
The value of two in the denominator is not a safe-ty factor. It is based on the theory that the slab panelwill move an equal distance from each end toward thecenter. This may not always be the situation (thus theexpanded definition of L). F, the friction factor, can varyfrom 0.5 upwards. A value of 2 should be used whenfurther information is not available.
Values of the coefficient of friction can vary sub-stantially as seen in Figure 2. In selecting a value, it isalways advisable to be conservative since subgradescan often be uneven resulting in a greater subgradefriction.
As previously stated, most floor slabs-on-ground havetheir thickness selected based on a given designprocedure (use Figure 3 for wheel load criteria). Thisprocedure may be the PCA design method, the WRIdesign procedure, the Corps of Engineers procedure
or the designer’s computer analysis. These proce-dures result in a thickness selection capable ofresisting a determined positive and negative momentbased on design input such as subgrade modulus,magnitude and location of loads and other factors.The bottom line is that the slab must be capable ofresisting a certain internal moment, possibly eitherpositive or negative. In the vicinity of a shrinkagecrack, this capacity has been compromised in thepast, if reinforcing such as welded wire reinforcing isnot present.
The needed moment capacity of the slab is simplythe modulus of rupture multiplied by the section mod-ulus. The minimum reinforcing is therefore likely to bethe steel area that has an ultimate capacity equal tothe design moment. This moment value would be thesection modulus multiplied by the working stress.Working stress is defined as the MOR divided by thesafety factor.
If we were to assume that a single layer of weldedwire reinforcing were located in the middle of the slab,the problem is simplified because the capacity is equalfor both positive and negative moment capacity. If wewere to assume the 6” thickness used in the previousprocedure and the working stress of the modulus ofrupture were 4 f’c the problem is further simplified.With these assumptions, the confirmed capacity pro-cedure simplifies to the following formula:
As = 14.5
where
As = cross-sectional area in square inches of steel per lineal foot of slab width
t = thickness of the slab in inches
f’c = compressive strength of the concrete (psi)
fy = yield stress of the reinforcement (psi)
A designer should consider the confirmed capacityprocedure as a reasonable minimum cross-sectionalarea for reinforcement of slabs-on-ground, as it willsecure a minimum moment capacity regardless ofshrinkage joint or crack location. Another version:
As = 4.4 x MOR x t
Note: SF is normally taken as 2. The first referencenoted on page 7 will provide the designer more back-ground on safety factors.
fy (SF)
fy
CONFIRMED CAPACITY PROCEDURE
Variation in values of coefficient of friction for five-inch slabson different bases and subbases.Source: “Design and Construction of Post-Tensioned Slabs on Ground,” Post-Tensioning Institute,1991.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 4 • TF 705-R-03
A procedure available for the control of crack size inslabs-on-ground can be found in the temperaturecontrol method. Concrete slabs-on-ground will, morethan likely, crack. Limiting the size of cracks can beeffected by placing sufficient welded wire reinforcing inthe slab to address the maximum change in temperaturethe slab is likely to experience. Climate controlledindustrial slabs-on-ground should normally bedesigned for a minimum temperature differential ortemperature gradient of 40°F. Slabs designed forextreme exposure should be designed for the maxi-mum extremes the climate dictates. This couldproduce a thermal gradient of 100°F or greater. Thisprocedure does not reduce cracking; however, itshould assist significantly in controlling crack widthsto maintain aggregate interlock. The temperaturemethod for checking the required reinforcement isstated as:
As = fr x 12 x t
where
As = the cross-sectional area in square inches of steel per lineal foot of slab width
t = thickness of slab in inches
fr = tensile strength of concrete (psi)(calculated at 0.4 x MOR)
fs = working stress in reinforcement (psi)
T = range of temperature the slab is expectedto be subjected to (°F)
∝= thermal coefficient of concrete (in/in°F)
Es = modulus of elasticity of steel (psi)
The normal range of the coefficient of thermalexpansion (∝) of concrete is 5 -7 x 10 -6 in/ in°F.
The intent is to minimize shrinkage crack frequencyand width based on anticipated temperaturechanges. The use of a thermal gradient of less than40°F is not recommended even in environmentallycontrolled conditions.
The equivalent strength procedure is referred to as theconcrete to steel ratio. The steel area is calculatedbased on 75% of the yield strength of the steel. Thetensile strength of the concrete is taken as 0.4 timesthe modulus of rupture (MOR). The modulus of rupturecan be safely taken as 7.5 f ‘c. This results in thefollowing formula:
As = 36
where
As = cross-sectional areas in square inches of steel per lineal foot of slab width
t = thickness of the slab in inchesf’c = compressive strength of the concrete (psi)fs = working stress in reinforcement (psi)
This method produces a significantly higher steelpercentage than normally encountered.
Use of this procedure will significantly reduce thefrequency of cracks in the 40-mill width range. It willnot eliminate them completely, however. Applicationsfor this design procedure are highway paving, airporttaxiways and runways and industrial building slabsand truck ramps, parking and roadways. See the list ofreferences for other sources of recommendations.
A procedure for providing maximum control of shrink-age cracks is available. The likelihood of its imple-mentation based on the steel requirements becomesrestrictive.
Although microcracking cannot be absolutelyguaranteed, the favorability of microcracking is
EQUIVALENT STRENGTH PROCEDURE
CRACK RESTRAINT PROCEDURE2(fs -T∝Es)
fs
TEMPERATURE PROCEDURE
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 5 • TF 705-R-03
dependent on the shrinkage potential of the concrete.For most industrial floors this can be taken as:
As = 9360t
where
As = cross-sectional area in square inches of steel perlineal foot of slab width
t = thickness of the slab in inches
fy = yield strength of steel reinforcing
This formula is the result of equating unit concreteshrinkage to a steel cross sectional area capable ofresisting this potential change in length. This proce-dure would be applied primarily to food processingoperations, hospitals and other applications requiringmore restraint of microcracking, which works out to 1%of the slab cross sectional area. A simple derivation ofthe crack restraint formula can be found in Appendix 2.
It is recommended that the designer at leastcheck the subgrade drag equation and the confirmedcapacity equation in selecting welded wire reinforcingfor slabs-on-ground. The greater value of the twoprocedures is suggested to be a minimum cross-sectional area requirement.
It is important for the designer to keep in mind thatunless joint spacings are extremely close, concretewill crack. It is therefore necessary to provide theowner with the security that the slab will function withminimal maintenance when cracks and crack widthsare kept to a minimum. Confirmed capacity designoffers this security to the owner, contractor and thedesign professional.
Subgrade Drag Procedure
fy
APPENDIX 1
Note: Larger styles are used when joint spacings and slabthicknesses are larger than shown in the example. fy of65,000 psi min. is used for standard styles of WWR i.e.,4x4 and 6x6 spacings with W1.4 to w4 wire sizes.
These high-strength WWR sheets of 12 x 12 - D16 x D16compares to #4@12” rebar and can be used for slab ongrade,paving and parking lots.
Note that two smaller close-wedge wires provide greater spliceefficiency.
It only takes two workers to easily carry two 8’x 15’ sheetsof WWR, while rebar requires more expense to tie and placethe material.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 6 • TF 705-R-03
APPENDIX 2
Workers walk on or into wide spaced welded wire reinforcementwithout deflecting or displacing it during concrete placement.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
Page 7 • TF 705-R-03
Having described five different methods for the sizingof concrete WWR, it would be of interest to comparethe findings, given the similar basic data. The followinginput was used in the comparison table below:
Slab thickness = 4” or 6”F = 2 (coefficient of friction)Panel length = 20 feetf’c = 4000 psiReinforcement to be plain or deformed welded wirewith yield strengths from 65,000 to 80,000 psi.Temperature gradient = 50°FCoefficient of thermal expansion = 6.5 x 10 -6
Es = 29 x 10 6
See Appendices for examples and derivation offormulas.
Note: The last 4 procedures can utilize W (plain) or D(deformed) wires or a combination of both.
Contributed by:Robert B. Anderson, P.E., Consulting Engineer, New Orleans, LA
WRI Structural WWR Detailing Binder, 10 Chapters,section 2 has tables comparing areas and weights ofrebar and WWR with various yield strengths of wire.
Video, “A Visit to a Distribution Center ConstructionSite, A Contractor’s Views,”1995.
WRI Manual of Standard Practice, WWR 500, 1992,includes metric wire sizes and WWR styles, 1995.
Tests to Determine Performance of Deformed WeldedWire Fabric Stirrups, AC/ Structural Journal, 91-S22,Griezic, Cook & Mitchell.
Evaluation of Joint-Shear Provisions for Interior Beam-Column-Slab Connections Using High-StrengthMaterials, AC/ Structural Journal, 89-S10, Guimaraes,Kreger, Jirsa.
Ductility of Wire Reinforcing - Industry Evaluation ofWWR Elongation and Reduction of Area, 1992.Means Concrete & Masonry Cost Data, 1996.
Some Observations on the Physical Properties of Wirefor Plain and Deformed Welded Wire, A.B. Dove, AC/Journal Technical Paper, 1983.
AC/, Design and Construction of Concrete Slabs onGrade, SCM-11 (86) with PCA’s Concrete Floors onGround, Third Edition inserted, p.10 DesignProcedure, Vehicle Loads, and p.12 High-Rack-Storage-Leg Loads.
PCA, Design of Concrete Airport Pavement, Chapter5, Steel in Jointed Pavements, Distributed Steel,Robert G.Packard.
CRSI, Placing Reinforcing Steel, 6th Edition, Chapter15, Highway and Airport Pavement, ContinuouslyReinforced Concrete Pavement and JointedReinforced Concrete Pavement.
REFERENCES
This report is furnished as a guide to industry practice. TheWire Reinforcement Institute (WRI) and its members make nowarranty of any kind regarding the use of this report for otherthan informational purposes. This report is intended for the useof professionals competent to evaluate the significance andlimitations of its contents and who will accept the responsibilityfor the application of the material it contains. WRI provides theforegoing material as a matter of information and, therefore, dis-claims any and all responsibility for application of the stated prin-ciples or the accuracy of the sources other than material devel-oped by the Institute.
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
TECH FACTS
www.wirereinforcementinstitute.org
Excellence Set in ConcreteWIRE REINFORCEMENT INSTITUTE®
U.S. Customary (inch-pound) Wire Sizes and AreasTABLE 2 - Sectional Areas of Welded Wire Reinforcement
Wire Size Number* Nominal Nominal Area in Sq. In. Per Ft. Of Width For Various Spacing(area of steel x 100) Diameter Weight Center-To-Center Spacing
Note: The above listing of plain wire sizes represents wires normally selected to manufacture welded wire reinforcementstyles to specific areas of reinforcement. Wires may be deformed using prefix D, except where only W is required onbuilding codes (usually less than W4). Wire sizes other than those listed above may be available if the quantity requiredis sufficient to justify manufacture.
*The number following the prefix W identifies the cross-sectional area of the wire in hundredths of a square inch.
The nominal diameter of a deformed wire is equivalent to the diameter of a plain wire having the same weight per foot as thedeformed-wire.
Refer to ACI 318 for The ACI Building Code requirements for tension development lengths and tension lap splicesof welded wire reinforcement. For additional information see Welded Wire Reinforcement Manual of StandardPractice and Structural Welded Wire Reinforcement Detailing Manual, both published by the Wire ReinforcementInstitute.
Page 8 • TF 705-R-03
942 Main Street • Suite 300 • Hartford, CT 06103 (800) 552-4WRI [4974]
III. Welded Wire Reinforcement: Nomenclature and Production 6
IV. Design Codes and Specifications 7
V. Advantages of Bending Welded Wire Reinforcement 8
VI. Bent Welded Wire Reinforcement: Many Applications 9
VII. Design Tables 12
Original Copyright 1981 Wire Reinforcement InstituteManual WWR-400-R Printed in U.S.A.
10th Publishing, 2003
This manual is furnished as a guide for the selection of welded wire reinforcementwith the understanding that, while every effort has been made to assure accuracy, neitherWire Reinforcement Institute, Inc., nor its member-companies, makes any warranty of anykind respecting the use of the manual for other than informational purposes.
WWR 400-R-03
www.wirereinforcementinstitute.org
Page 3 • WWR 400-R-03
Where construction requires the repetitiousbending and shaping of reinforcement,welded wire reinforcement has resulted infaster and more economical production.The development of new hydraulic equip-ment now simplifies the production of rein-forcement cages made form sheets ofwelded wire. Research and constructionexperience using wire reinforcement withits design strength equivalent to or greaterthan grade 60 reinforcing bars, show excel-lent time savings and sound design perfor-mance. The fabrication and placement oflarge sections of reinforcement made fromwelded wire reinforcement provide opti-mum use of labor and simplify projectsupervision and inspection.
Formed into shapes for beam stirrups, col-umn ties, corner reinforcement and otherconfigurations, welded wire has increased
savings in placement time in both pre-caseand cast-in-place construction. Duringrecent construction of a high rise officebuilding the contractor converted from indi-vidual bar stirrups to welded wire reinforce-ment for stirrup cages and experienced a75% savings in time and labor for the rein-forcement placement. In forming cages forutility vaults, precasters have cut assemblytime from three hours, using rebars, to only40 minutes, using welded wire reinforce-ment. Contractors have found that rein-forcement, used as shear reinforcement forprestressed double tees, may be easily andconfidently positioned without fear of thereinforcement shifting during tensioningand concrete placement.
In planning your next project consider theadvantages of bent welded wire reinforce-ment as outlined in the following pages.
I. INTRODUCTION
www.wirereinforcementinstitute.org
II. EQUIPMENT
The fabrication of welded wire reinforcement intovarious structural shapes is readily accomplishedwith two basic pieces of portable equipment, abending machine and a cutting device.
The bending machine provides the flexibility ofadjusting to various wire spacings, angles of bendand bending radii. This equipment is manufacturedin sizes ranging in length from 8 to 40 feet.Capacities range from the small wire sizes usedprimarily in precast operations to heavy W45 struc-tural wires, 0.757 in. diameter. The sheets of weld-ed wire are bent on the machine by an arm whichrotates through an angle of 0° to 180°, shaping thewires around the mandrels. This arm can be pre-set to stop at any angle and the mandrels can bevaried to meet the design requirement for bendradius and wire spacing.
The cutting equipment can be a simple hand toolcapable of cutting one wire at a time or larger pow-ered equipment which cuts the full width of a sheetin one operation. This powered equipment allows theuse of more economically manufactured sheets of wirereinforcement.
The bending and cutting equipment are compara-tively low cost investments which require no spe-cial skills for efficient operation. Both machines,operating on electric power, can be conveniently
moved from one project to another, lending them-selves very readily to on-site construction, precastoperations and use in fabricating shops.
Bending machineprovides flexibility ofadjustment to meetdesign requirements.
Various mandrel sleeve diameters can be used to obtaindesired bending radii.
Welded Wire Reinforcement manufactured for concrete pipe.
Page 4 • WWR 400-R-03
www.wirereinforcementinstitute.org
TYPICAL BENDING SEQUENCE
Making a Stirrup
3RD BEND: Sheet has been advanced into machine and now another 90° bend has been made.
4TH BEND: Bending arm is rotating and putting the final 90° bend into fabric shape.
START: Workers feed sheet of welded wire under mandrels.
1ST & Bending arm (left) is rotating and2ND BENDS: putting 90° bend into end of
sheet. Other end of sheet next willbe shaped identically.
COMPLETION: Stirrup is completed and ready for removal from the machine.
Page 5 • WWR 400-R-03
www.wirereinforcementinstitute.org
III. WELDED WIRE REINFORCEMENT: NOMENCLATURE & PRODUCTIONWelded wire is produced from a series of longitudi-nal and transverse high strength steel wires, resis-tance welded at all intersections. The wires are pro-duced from controlled-quality hot-rolled rods whichare cold-drawn through a series of dies reducingthe rod to the specified wire diameter. This wire isthen fed into a rigid grid of reinforcement. Themanufacturing process can be varied to accom-modate various style changes and dimensions.However, consideration should be given to the com-plexity of the change. The manufacturing variablesare listed in the general order of time involved,starting with the most time consuming:
1. Longitudinal wire spacing2. Longitudinal wire size3. Width4. Side and end overhangs5. Transverse wire size6.Transverse wire spacing7.Length
The more difficult machine changes requiregreater quantities per item, in order to offset theadditional production time required. Generally, it ismore economical to order a few basic sheet sizesand styles than to specify many variations in thesheet. Quantity requirements for each changeusually vary between producers.
The cross-sectional steel area is the basic ele-ment used in specifying the required wire size. The
nomenclature used to indicate wire size is a letterfollowed by a number. The letter "W" identifies aplain wire and the letter "D" a deformed wire. Thenumber which follows is the cross-sectional areaof the wire given in hundredths of a square inch.For example: W16 denotes a plain wire withcross-sectional area of 0.16 sq. in.; D7.5 indicatesa deformed wire with a cross-sectional area of0.075 sq. in.
The welded wire reinforcement style identifies thespacing and size of the transverse and longitudi-nal wires and takes the format: 6 x 12—W16 xW8, where the longitudinal wire spacing is 6 in.with wire size W16 and the transverse wire spac-ing is 12 in. with wire size W8.
The complete designation also includes thedimensions of the fabric sheet such as: 90", (+1"+3") x 20—0" where the width (given in inches) isequal to 90 in., with side overhangs of 1 in. on oneside and 3 in. on the other for an overall width of94 in., and the length is equal to 20 ft.—O in. Thestandard end overhang, equal to one half thetransverse wire spacing, is assumed unless oth-erwise specified. It is important to note that thelength is the tip-to-tip dimension of the longitudinalwire (20 ft.—0 in. in above example) and that thetip-to-tip dimension of the transverse wires iscalled the overall width, equal to the width plusboth side overhangs (94 in. in above example).
Side Overhangs may be variedas required and do not need tobe equal. Overhang lengthslimited only by overall sheet width.
End Overhangs may differ.Thesum of the end overhangs,however, should equal thetransverse wire spacing.
Longitudinal wire��Transverse wire
Overall Width
WidthLength
Industry Method of Designating StyleExample – 6x12 – W16 x W8
Transversewire spacing
Transversewire size
Longitudinalwire spacing
Longitudinalwire size
WELDED WIREREINFORCEMENT NOMENCLATURE
Page 6 • WWR 400-R-03
www.wirereinforcementinstitute.org
SPECIFICATIONS• Welded wire reinforcement, both plain and deformed, is
defined as deformed reinforcement (Ref. ACI 318,Section 2.1).
• Current ASTM Standards for welded wire allow up to 80,000 psi yield strength and refer to local buildingcodes for stress/strain tests when structural welded wirereinforcement is specified. If 60,000 psi, fy or lower isspecified, the ASTM Standards state that fy shall be thestress corresponding to a strain of 0.50%. The ACI build-ing code states that when yield strength, fy exceeds60,000 psi, fy shall be the stress corresponding to astrain of 0.35%. (Ref. ACI 318, Sections 3.5.3.4,3.5.3.5 and 3.5.3.6)
BENDS AND HOOKS: (Ref. ACI 318, Section 7.2.3) Inside diameter of bends in welded wire used for stirrupsand ties shall not be less than four wire diameters fordeformed wire larger than D6 and two wire diameters forall other wires, both plain and deformed. Bends with insidediameters of less than eight wire diameters shall not be lessthan four wire diameters from nearest welded intersection.
LATERAL REINFORCEMENT• Equivalent areas of welded wire may be used to furnish
the lateral reinforcement requirements specified in ACI318, Section 7.11.
• Design yield strength of shear reinforcement shall not exceed 60,000 psi, except that the design yield strengthof welded deformed wire shall not exceed 80,000 psi.(Ref. ACI 318, Section 11.5.2).
• Design yield strength of nonprestressed torsion rein-forcement shall not exceed 60,000 psi. (Ref. ACI 318,Section 11.6.3.4)
• Anchorage of web reinforcement for each leg of a simpleU-shaped stirrup formed from welded wire must meet oneof the following: (Ref. ACI 318, Section 12.13.2.3).
(1) Welded wire may be used as shear reinforcementwhen the wires are located perpendicular to the axis of themember. (Ref. ACI 318, Section 11.5.1.1,b)
(2) One longitudinal wire located not more than d/4 fromthe compression face and a second wire closer to the com-pression face and spaced not less than 2 in. from the firstwire. The second wire shall be permitted to be located onthe stirrup leg beyond a bend, or on a bend with an insidediameter of bend not less than8 wire diameters.
EPOXY-COATED WIRES AND WELDED WIREWhen epoxy-coated wire or welded wire is specified, itshall comply with the “Specification for Epoxy-Coated
Steel Wire and Welded Wire for Reinforcement” (ASTM A 884) (Ref. ACI 318, Section 3.5.3.8)
2"
(51mm)
d/4maximum
d/4maximum
d/4maximum
Minimum of 2”(51mm)
8 wire diameterbend (minimum)
ANCHORAGE OF WEB REINFORCEMENT USINGWELDED WIRE (Non-Seismic Applications)
Consecutive crosstiesengaging the same lon-gitudinal bars shall havetheir 90-deg hooks onopposite sides
6db (≥ 3 in.)
6db (≥ 3 in.)
Extension
Detail B
Detail C
6db Extension
6db Extension
B
C
X X X
X
X
CAA
Crosstie asdefined in 21.1
Consecutive crosstiesengaging the samelongitudinal bars shall havetheir 90-deg hooks onopposite sides of columns
X shall not exceed 14 inches
Fig. R21.3.3 – Example of overlapping hoops
Fig. R21.4.4 – Example of transverse reinforcementin columns
IV. DESIGN CODES AND SPECIFICATIONSThe use of welded wire as a structural concrete reinforcing material is governed by codes such as the ACI 318 BuildingCode and by specifications such as ASTM A-82, A-185, A-496, and A-497. These references provide the necessary crite-ria for designing with the unique structural grid of reinforcement provided by welded wire. The following is a summary ofACI code specifications which pertain to the use of bent welded wire:
V. ADVANTAGES OF BENDING WELDED WIRE REINFORCEMENT
Bending welded wire fabric literally adds a third dimension to concrete reinforcement. It provides thestructural engineer with new options in design. The welded wire can be bent to the desired shape andplaced where it is needed. Equally important, the contractor can be reasonably sure that it will remainintact as placed. Here are some of its many advantages:
EXCELLENT BONDING AND DEVELOP-MENT CHARACTERISTICS
The welded cross wires of welded wire reinforce-ment provide unique anchorage for the reinforce-ment. ACI 318 code provides for the use of eitherhooked or straight "U" stirrups when designedfrom wire reinforcement. The straight "U - shapedstirrup can be designed from plain welded wirewhen at least two separate longitudinal wires arelocated in the anchorage zone. The use of the "U"shaped stirrups eliminates several bends allowingstirrup cages to be formed in less time. Effectivedesigns using welded deformed wire for stirrupshave been developed using both the develop-ment length of the deformed wire in addition tothe weld shear strength, to meet anchoragerequirements.
OPTIMUM USE OF LABOR/SIMPLIFIEDSUPERVISION
Equipment is basic and easily operated byconstruction crews who require no special training.Sections of bent welded wire reinforcement, withthe steel spacing already fixed, are quickly set intoplace, therefore reducing supervision and simplify-ing inspection of the reinforcement.
BETTER CRACK CONTROL
The high efficiency of small wire sizes and closelyspaced reinforcement serves to distribute andequalize the stresses that may result in cracking.Research' has shown that closely spaced wires, 2to 4in. apart, in welded wire represent the mostfavorable type of reinforcement for shear and tor-sion.
MINIMIZES WELDING PROBLEMS
Because welded wire reinforcement is made formlow carbon, cold-drawn steel it has greater weld-ability, therefore reducing special fabrication prob-lems.
BENDING AND PLACEMENTTIME REDUCED
Fabrication and placement of individual rebars asstirrups takes up to five times longer than bentunits of welded wire, depending on the stirrupspacing.2 Only when stirrup spaces were greaterthan 30 in. were the individual bars found more eco-nomical.
2 “Welded Wire for Web Reinforcement—Beam Tests," reportby Arthur Anderson, ABAM Engineers, Inc., Tacoma, Wash.
TIME STUDY-STIRRUP BENDING & PLACEMENT 2
ST
IRR
UP
SP
AC
ING
, in
ches
TIME, minutes0 60 120 180 240
10
20
30
40
50
60
Welded wire Stirrups
Rebar Stirrups
Page 8 • WWR 400-R-03
www.wirereinforcementinstitute.org
ADVANTAGES OF BENT WIRE REINFORCEMENT . . .
CAST-IN-PLACE CONSTRUCTION
VI. BENT REINFORCEMENT: MANY APPLICATIONS
TIME SAVED IS MONEY
Bent welded wire reinforcement can save moneytwo ways—particularly on large, complicated jobs.First, it reduces the time required to place the rein-forcement. Second, in many instances, it canspeed up construction cycles. For instance, thecontractor on a major structure recently reducedhis time per floor slab from 10 days to 6 days. Thisjob was large and involved complicated reinforce-ment. It is an unusual case, but indicative of pos-sible savings in time that can speed up the job.
IMPORTANT IN MEETING COVERREQUIREMENTS
Concrete cover requirements are by necessityboth stringent and critical. Here again the rigidityof bent welded wire helps contractors meet coverrequirements.
HELPS MEET LACING TOLERANCES
The intersecting wires of welded wire reinforcementare firmly welded together and thus do not slip outof place. Welding also gives the reinforcement acertain degree of rigidity which is helpful during con-crete placement. Thus bent welded wire reinforce-ment is easy to place and helps assure that rein-forcement is positioned exactly where it is supposedto be after placement of the concrete.
PORTABLE AND FLEXIBLE EQUIPMENT
The bending and cutting equipment for weldedwire reinforcement can be easily set up on loca-tion, providing close coordination and control of theproduction of the bent reinforcement. Angles anddiameter of the bend can be easily adjusted tomeet the design. Shaping the reinforcement onthe job site or at the fabricating plant also allowsthe welded wire reinforcement to be shipped moreeconomically as flat sheets.
Recent highrise construction projects have shownsignificant savings when using welded wire stirrupreinforcement:
• Midway through construction of a 32story ofoffice building the stirrup reinforcement was con-verted from bars to welded wire. “once the stirrupswere used, production shot up, steel placementcosts dropped and the slab construction cycle wasreduced from 9-10 days to 6 days . . . for atime/labor savings of 75%.”
• Contractors on similar highrise construction pro-jects have reported reduction in bending andplacement of stirrups from 16 man-hours per tonfor rebar stirrups to 8 man-hours per ton to placewelded wire reinforcement stirrups.
Placing Stirrup
BEAM
Page 9 • WWR 400-R-03
www.wirereinforcementinstitute.org
OTHER CAST-IN-PLACE APPLICATIONS
PRECAST/PRESTRESSED CONSTRUCTIONThe preshaping and assembly ofwelded wire reinforcement is anatural time saver in the produc-tion of precast/ prestressed prod-ucts:• The precaster of utility vaults,box culverts and other under-ground precast productsachieved a significant savings inreinforcing case assembly time
by using welded wire reinforcement. The assembly of the rein-forcement for a typical manhole structure 6'x12'x6' oncerequired three hours to assemble from bars. With welded wirethis same cage takes 40 minutes.
• The use of shapedwelded wire reinforce-ment results in similarsavings of time andmoney in the produc-tion of prestressed boxbeams and single anddouble-tee beams.
• Welded wire reinforcement,shaped to the contours of 3-tiered risers for a large stadi-um, helped the precaster ofthese prestressed componentsto achieve assembly line effi-ciency by reducing handlingand placement time for thereinforcement. The wire rein-forcing's rigidity assured cor-rect position in the riser formsand correct concrete cover.
Placing WWR Welded wire cage in a box culvert form.
