Longspan and Deep Longspan Steel Joists are relatively lightweight shop-fabricated steel trusses. Longspan Steel Joists are used for the direct support of floor or roof slabs or decks between walls, beams, and main structural mem- bers. Deep Longspan Steel Joists are used for the direct support of roof slabs or decks between walls, beams and main structural members. The LH- and DLH-Series have been designed for the pur- pose of extending the use of joists to spans in excess of those covered by Open Web Joists. Longspan Series Joists have been standardized in depths from 18" (457 mm) through 48" (1219 mm), for clear spans through 96 feet (29260 mm). Deep Longspan Series Joists have been standardized in depths from 52" (1321 mm) through 72" (1829 mm), for clear spans up through 144 feet (43891 mm). Longspan and Deep Longspan Steel Joists can be furnished with either underslung or square ends, with par- allel chords or with single or double pitched top chords to provide sufficient slope for roof drainage. Square end joists are primarily intended for bottom chord bearing. Sloped parallel-chord joists shall use span as defined by the length along the slope. The joist designation is deter- mined by its nominal depth at the center of the span and by the chord size designation. The depth of the bearing seat at the ends of underslung LH- DLH- Longspan Joists has been established at 5" (127 mm) for chord sizes #2 through #17. A bearing seat depth of 7¹⁄₂ inches (191 mm) has been established for the DLH- Series chord sizes #18 and #19. All Longspan and Deep Longspan Steel Joists are fabricat- ed with standardized camber as listed in paragraph 103.6. The illustrations above indicate Longspan and Deep Longspan Steel Joists with modified WARREN type web systems. However, the web systems may be any type, whichever is standard with the manufacturer furnishing the product. Where Longspan or Deep Longspan Joists are supported on structural steel members, the connection is generally field welded. The number, size and length of welds should be specified. Where bolted connections are specified, slot- ted holes are provided in the bearing seats for this purpose. 41 LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH- SERIES Parallel Chords, Underslung Parallel Chords, Square Ends Top Chord Pitched One Way, Underslung Top Chord Pitched One Way, Square Ends Top Chord Pitched Two Ways, Underslung Top Chord Pitched Two Ways, Square Ends INTRODUCTION STANDARD TYPES ACCESSORIES BOLTED CONNECTIONS CEILING EXTENSION LONGSPAN JOISTS FOR FLOOR CONSTRUCTION ON STRUCTURAL STEEL LONGSPAN AND DEEP LONGSPAN JOISTS FOR ROOF CONSTRUCTION ON STRUCTURAL STEEL COLUMNS
Transcript
Longspan and Deep Longspan Steel Joists are relativelylightweight shop-fabricated steel trusses. Longspan SteelJoists are used for the direct support of floor or roof slabsor decks between walls, beams, and main structural mem-bers. Deep Longspan Steel Joists are used for the directsupport of roof slabs or decks between walls, beams andmain structural members.
The LH- and DLH-Series have been designed for the pur-pose of extending the use of joists to spans in excess ofthose covered by Open Web Joists.
Longspan Series Joists have been standardized in depthsfrom 18" (457 mm) through 48" (1219 mm), for clear spansthrough 96 feet (29260 mm).
Deep Longspan Series Joists have been standardized indepths from 52" (1321 mm) through 72" (1829 mm), forclear spans up through 144 feet (43891 mm).
Longspan and Deep Longspan Steel Joists can be furnished with either underslung or square ends, with par-allel chords or with single or double pitched top chords toprovide sufficient slope for roof drainage. Square end joistsare primarily intended for bottom chord bearing.
Sloped parallel-chord joists shall use span as defined bythe length along the slope. The joist designation is deter-mined by its nominal depth at the center of the span and bythe chord size designation.
The depth of the bearing seat at the ends of underslungLH- DLH- Longspan Joists has been established at 5" (127mm) for chord sizes #2 through #17. A bearing seat depthof 7¹⁄₂ inches (191 mm) has been established for the DLH-Series chord sizes #18 and #19.
All Longspan and Deep Longspan Steel Joists are fabricat-ed with standardized camber as listed in paragraph 103.6.
The illustrations above indicate Longspan and DeepLongspan Steel Joists with modified WARREN type websystems. However, the web systems may be any type,whichever is standard with the manufacturer furnishing theproduct.
Where Longspan or Deep Longspan Joists are supportedon structural steel members, the connection is generallyfield welded. The number, size and length of welds shouldbe specified. Where bolted connections are specified, slot-ted holes are provided in the bearing seats for this purpose.
41
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
Parallel Chords, Underslung
Parallel Chords, Square Ends
Top Chord Pitched One Way, Underslung
Top Chord Pitched One Way, Square Ends
Top Chord Pitched Two Ways, Underslung
Top Chord Pitched Two Ways, Square Ends
INTRODUCTION
STANDARD TYPES
ACCESSORIES
BOLTEDCONNECTIONS
CEILINGEXTENSION
LONGSPAN JOISTS FOR FLOOR CONSTRUCTION ON STRUCTURAL STEEL
LONGSPAN AND DEEPLONGSPAN JOISTS FOR ROOFCONSTRUCTION ONSTRUCTURAL STEEL COLUMNS
These specifications cover the design, manufacture anduse of Longspan Steel Joists LH-Series, and DeepLongspan Steel Joists, DLH-Series.
The term “Longspan Steel Joists LH-Series and DeepLongspan Steel Joists DLH-Series”, as used herein, refersto open web, load-carrying members utilizing hot-rolled orcold-formed steel, including cold-formed steel whose yieldstrength* has been attained by cold working. LH-Seriesare suitable for the direct support of floors and roof decks inbuildings, and DLH-Series are suitable for direct support ofroof decks in buildings.
The design of LH- and DLH-Series joist chord and websections shall be based on a yield strength of at least 36 ksi(250 MPa), but not greater than 50 ksi (345 MPa). Steelused for LH- and DLH-Series joist chord or web sectionsshall have a minimum yield strength determined in accor-dance with one of the procedures specified in Section102.2, which is equal to the yield strength assumed in thedesign. LH- and DLH-Series joist shall be designed inaccordance with these specifications to support the loadsgiven in the attached Standard Load Tables for LH- andDLH-Series joists.
* The term “Yield Strength” as used herein shall designatethe yield level of a material as determined by the applicablemethod outlined in paragraph 13.1, “Yield Point” and inparagraph 13.2, “Yield Strength”, of ASTM Standard A370,“Standard Test Methods and Definitions for MechanicalTesting of Steel Products”, or as specified in Section102.2 of this Specification.
102.1 STEELThe steel used in the manufacture of chord and web sec-tions shall conform to one of the following ASTMSpecifications:
• Steel, Sheet and Strip, Hot-Rolled, Carbon,Structural, High-Strength Low-Alloy and High-Strength Low-Alloy with Improved Formability,ASTM A1011/A1011M.
or shall be of suitable quality ordered or produced to otherthan the listed specifications, provided that such material inthe state used for final assembly and manufacture is weld-able and is proved by tests performed by the producer ormanufacturer to have the properties specified in Section102.2.
102.2 MECHANICAL PROPERTIESThe yield strength used as a basis for the design stressesprescribed in Section 103 shall be at least 36 ksi (250MPa), but shall not be greater than 50 ksi (345 MPa).Evidence that the steel furnished meets or exceeds thedesign yield strength shall, if requested, be provided in theform of an affidavit or by witnessed or certified test reports.
For material used without consideration of increase in yieldstrength resulting from cold forming, the specimens shall betaken from as-rolled material. In the case of material, the
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STANDARD SPECIFICATIONSFOR LONGSPAN STEEL JOISTS, LH-SERIES AND DEEP LONGSPAN STEEL JOISTS, DLH-SERIES
ANSI Designation: SJI-LH/DLH-1.0Adopted by the Steel Joist Institute February 15, 1978
Revised to May 1, 2000 – Effective August 1, 2002
SECTION 100.
SCOPE
SECTION 101.
DEFINITION
Standard Specifications and Load Tables, Longspan SteelJoists, LH-Series and Deep Longspan Steel Joist DLH-Series
Steel Joist Institute – Copyright, 2002
SECTION 102.
MATERIALS
mechanical properties which conform to the requirementsof one of the listed specifications, test specimens and pro-cedure shall conform to those of such specifications and toASTM A370.
In the case of material, the mechanical properties which donot conform to the requirements of one of the listed speci-fications, the test specimens and procedures shall conformto the applicable requirements of ASTM A370, and thespecimens shall exhibit a yield strength equal to or exceed-ing the design yield strength and an elongation of not lessthan (a) 20 percent in 2 inches (51 mm) for sheet and strip,or (b) 18 percent in 8 inches (203 mm) for plates, shapesand bars with adjustments for thickness for plates, shapesand bars as prescribed in ASTM A36/A36M, A242/A242M,A529/A529M, A572/A572M, A588/A588M, whicheverspecification is applicable on the basis of design yieldstrength.
The number of tests shall be as prescribed in ASTMA6/A6M for plates, shapes, and bars; and ASTMA570/A570M, A606, A607, and A611 for sheet and strip.
If as-formed strength is utilized, the test reports shall showthe results of tests performed on full section specimens inaccordance with the provisions of the AISI Specificationsfor the Design of Cold formed Steel Structural Membersand shall indicate compliance with these provisions andwith the following additional requirements:
(a) The yield strength measured in the tests shall equal orexceed the design yield strength.
(b) Where tension tests are made for acceptance and con-trol purposes, the tensile strength shall be at least 6percent greater than the yield strength of the section.
(c) Where compression tests are used for acceptance andcontrol purposes, the specimen shall withstand a grossshortening of 2 percent of its original length withoutcracking. The length of the specimen shall be notgreater than 20 times its least radius of gyration.
(d) If any test specimen fails to pass the requirements ofsubparagraphs a, b, and c above, as applicable, tworetests shall be made of specimens from the same lot.Failure of one of the retest specimens to meet suchrequirements shall be the cause for rejection of the lotrepresented by the specimens.
102.3 WELDING ELECTRODESThe following electrodes shall be used for arc welding:
(a) For connected members both having a specified mini-mum yield strength greater than 36 ksi (250 MPa).
AWS A5.1 or A5.5, E70XXAWS A5.17, F7XX -EXXX flux electrode combination AWS A5.18, E70S-X or E7OU-1AWS A5.20, E7OT-X
(b) For connected members both having a specified mini-mum yield strength of 36 ksi (250 MPa) or one having
a specified minimum yield strength of 36 ksi (250MPa), and the other having a specified minimum yieldstrength greater than 36 ksi (250 MPa).
Other welding methods, providing equivalent strength asdemonstrated by tests, may be used.
102.4 PAINTThe standard shop paint is intended to protect the steel foronly a short period of exposure in ordinary atmosphericconditions and shall be considered an impermanent andprovisional coating.
When specified, the standard shop paint shall conform toone of the following:
(a) Steel Structures Painting Council Specification, SSPCNo. 15
(b) Or, shall be a shop paint which meets the minimumperformance requirements of the above listed specifi-cation.
103.1 METHODJoists shall be designed in accordance with these specifi-cations as simply supported, uniformly loaded trusses sup-porting a floor or roof deck so constructed as to brace thetop chord of the joists against lateral buckling. Where anyapplicable design feature is not specifically covered herein,the design shall be in accordance with the following speci-fications.
(a) American Institute of Steel Construction Specificationfor Design, Fabrication and Erection of Structural Steelfor Buildings (Allowable Stress Design), where thematerial used consists of plates, shapes or bars.
(b) American Iron and Steel Institute Specification for theDesign of Cold-Formed Steel Structural Members, formembers which are formed from sheet or strip materi-al.
103.2 UNIT STRESSESJoists shall have their components so proportioned that theunit stresses in kips per square inch (Mega Pascals) shallnot exceed the following, where Fy is the yield strengthdefined in Section 102.2:
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
43
SECTION 103.
DESIGN AND MANUFACTURE
(b) CompressionFor members with Kl/r less than Cc:
where Q is a form factor equal to unity except when thewidth-thickness ratio of one or more elements of theprofile exceeds the limiting width-thickness ratios fornoncompact sections specified in the AISCSpecifications, Section B5 (Allowable Stress Design)for hot-rolled sections; where K is a length factor usedto determine the effective slenderness ratio as shownin Table 103.3.1.
For cold-formed sections, the method of calculating theallowable column design strength is given in the AISISpecification.
For members with Kl/r greater than Cc:
In the above formulas, Kl/r taken as the appropriateeffective slenderness ratio as determined from Section103.3 and “E” is equal to 29,000 ksi (200,000 MPa).
(c) Bending:For chords and web members other than solid rounds
Fb = 0.6Fy
For web members of solid round cross sectionFb = 0.9Fy
For bearing platesFb = 0.75Fy
(d) Weld Stresses:Shear at throat of fillet welds:
Made with E70 series electrodes or F7XX-EXXX-Xflux-electrode combinations. . . . . . . . . . 21 ksi (145MPa)
Made with E60 series electrodes or F6XX-EXXX-Xflux-electrode combinations . . . . . . . . . .18 ksi (124MPa)
Tension or compression on groove or butt welds shallbe the same as those specified for the connectedmaterial.
103.3 MAXIMUM SLENDERNESS RATIOSThe slenderness ratios, 1.0l/r and 1.0ls/r of members as awhole or any component part shall not exceed the valuesgiven in Table 103.3.1, Parts A.
The effective slenderness ratio, Kl/r*, to be used in calcu-lating the allowable stresses Fa and F'e, is the largest valueas determined from Table 103.3.1, Parts B and C.
In compression members when fillers or ties are used, theyshall be spaced so that the ls/rz ratio of each componentdoes not exceed the governing l/r ratio of the member as awhole. The terms are defined as follows:
l = Length center-to-center of panel points, except l = 36"(914 mm) for calculating l/ry of top chord member.
* See AISC Specification Section C2.1 and P.N. Chod and T.V. Galambos, Compression Chords Without Fillers inLongspan Steel Joists, Research Report No. 36, June 1975Structural Division, Civil Engineering Department,Washington University, St. Louis, MO.
Fa = ( )2
2
rK23E12
!
π
Fa =
( )
3
cc
y2c
2
CrK
81
CrK
83
35
QF2C
rK1
−
+
−
!!
!
where Cc = y
2
QFE2π and
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
44
TABLE 103.3.1MAXIMUM AND EFFECTIVE SLENDERNESS RATIOS
I TOP CHORD INTERIOR PANELA. The slenderness ratios, 1.0l/r and 1.0ls/r, of members as a whole or any component part shall not exceed 90.
B. The effective slenderness ratio to determine “Fa”
1. With fillers or ties 0.75l/rx 1.0l/ry 1.0ls/rz
2. Without fillers or ties 0.75l/rz
3. Single component members 0.75l/rx 1.0l/ry
C. The effective slenderness ratio to determine “F'e”
1. With fillers or ties 0.75l/rx
2. Without fillers or ties 0.75l/rx
3. Single component members 0.75l/rx
II TOP CHORD END PANELA. The slenderness ratios, 1.0l/r and 1.0ls/r, of members as a whole or any component part shall not exceed 120.
B. The effective slenderness ratio to determine “Fa”
1. With fillers or ties 1.0l/rx 1.0l/ry 1.0ls/rz
2. Without fillers or ties 1.0l/rz
3. Single component members 1.0l/rx 1.0l/ry
C. The effective slenderness ratio to determine “F'e”
1. With fillers or ties 1.0l/rx
2. Without fillers or ties 1.0l/rx
3. Single component members 1.0l/rx
III TENSION MEMBERS - CHORDS AND WEBSA. The slenderness ratios, 1.0l/r and 1.0ls/r, of members as a whole or any component part shall not exceed 240.
IV COMPRESSION WEB MEMBERSA. The slenderness ratios, 1.0l/r and 1.0ls/r, of members as a whole or any component part shall not exceed 200.
B. The effective slenderness ratio to determine “Fa”
1. With fillers or ties 0.75l/rx 1.0l/ry 1.0ls/rz
2. Without fillers or ties 1.0l/rz
3. Single component members 0.75l/rx* 1.0l/ry
* Use 1.2l/rx for a crimped, first primary compression web member when a moment-resistant weld group is not used for thismember.
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
45
ls = maximum length center-to-center between panel point and filler (tie), or between adjacent fillers (ties).
rx = member radius of gyration in the plane of the joist.
ry = member radius of gyration out of the plane of the joist.
rz = least radius of gyration of a member component.
103.4 MEMBERS(a) Chords
The bottom chord shall be designed as an axiallyloaded tension member.
The top chord shall be designed as a continuous mem-ber subject to combined axial and bending stressesand shall be so proportioned that
fa + fb ≤ 0.6 Fy at the panel point; and
Cm = 1 - 0.3fa/F'e for end panels
Cm = 1 - 0.4fa/F'e for interior panels
fa = Computed axial unit compressive stress
fb = Computed bending unit compressive stress at thepoint under consideration
Fa = Permissible axial unit compressive stress basedon Kl/r.
Fb = Permissible bending unit stress; 0.6Fy
F'e =
rx = Radius of gyration about the axis of bending
Q = Form factor as defined in Section 103.2(b).
The radius of gyration of the top chord about its verti-cal axis shall be not less than l/170 where l is thespacing in inches (millimeter) between lines of bridgingas specified in Section 104.5(d).
The top chord shall be considered as stayed laterallyby the floor slab or roof deck provided the require-ments of Section 104.9(e) of these specifications aremet.
(b) WebThe vertical shears to be used in the design of the webmembers shall be determined from full uniform load-ing, but such vertical shears shall be not less than 25percent of the end reaction.
Interior vertical web members used in modified Warrentype web systems shall be designed to resist the grav-ity loads supported by the member plus ¹⁄₂ of 1.0 per-cent of the top chord axial force.
(c) Depth Joists may have either parallel chords or a top chordslope of ¹⁄₈ inch per foot (1:96). The depth, for the pur-pose of design, in all cases shall be the depth at mid-span.
(d) EccentricityMembers connected at a joint shall have their center ofgravity lines meet at a point, if practical. Eccentricity oneither side of the neutral axis of chord members maybe neglected when it does not exceed the distancebetween the neutral axis and the back of the chord.Otherwise, provision shall be made for the stressesdue to eccentricity. Ends of joists shall be proportionedto resist bending produced by eccentricity at the sup-port.
In those cases where a single angle compressionmember is attached to the outside of the stem of a teeor double angle chord, due consideration shall begiven to eccentricity.
(e) Extended EndsExtended top chords or full depth cantilever endsrequire the special attention of the specifying profes-sional. The magnitude and location of the design loadsto be supported, the deflection requirements, and theproper bracing shall be clearly indicated on the struc-tural drawings.
103.5 CONNECTIONS(a) Methods
Joist connections and splices shall be made by attach-ing the members to one another by arc or resistancewelding or other approved method.
1) Welded Connections
a) Selected welds shall be inspected visually bythe manufacturer. Prior to this inspection, weldslag shall be removed.
b) Cracks are not acceptable and shall berepaired.
c) Thorough fusion shall exist between layers ofweld metal and between weld metal and basemetal for the required design length of the weld;such fusion shall be verified by visual inspec-tion.
d) Unfilled weld craters shall not be included in thedesign length of the weld.
e) Undercut shall not exceed 1/16 inch (2 mm) forwelds oriented parallel to the principal stress.
f) The sum of surface (piping) porosity diametersshall not exceed ¹⁄₁₆ inch (2mm) in any 1 inch (25mm) of design weld length.
g) Weld spatter that does not interfere with paintcoverage is acceptable.
2) Welding Program
Manufacturers shall have a program for establish-ing weld procedures and operator qualification,and for weld sampling and testing.
( )2x
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, at mid-panel; in which
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
46
3) Weld Inspection by Outside Agencies (SeeSection 104.13 of these specifications).
The agency shall arrange for visual inspection todetermine that welds meet the acceptance stan-dards of Section 103.5(a)(1) above. Ultrasonic,X-Ray, and magnetic particle testing are inappro-priate for joists due to the configurations of thecomponents and welds.
(b) StrengthJoint connections shall develop the maximum forcedue to any of the design loads, but not less than 50percent of the allowable strength of the member in ten-sion or compression, whichever force is the controllingfactor in the selection of the member.
(c) Shop SplicesShop splices may occur at any point in chord or webmembers. Splices shall be designed for the memberforce but not less than 50 percent of the allowablemember strength. Members containing a butt weldsplice shall develop an ultimate tensile force of at least57 ksi (393 MPa) times the full design area of the chordor web. The term “member” shall be defined as allcomponent parts comprising the chord or web, at thepoint of splice.
(d) Field SplicesField Splices shall be designed by the manufacturerand may be either bolted or welded. Splices shall bedesigned for the member force, but not less than 50percent of the allowable member strength.
103.6 CAMBERJoists shall have approximate cambers in accordance withthe following:
Top Chord Length Approximate Camber
20'-0" (6096 mm) ¹⁄₄" (6mm)
30'-0" (9144 mm) ³⁄₈" (10 mm)
40'-0" (12192 mm) ⁵⁄₈" (16 mm)
50'-0" (15240 mm) 1" (25 mm)
60'-0" (18288 mm) 1¹⁄₂" (38 mm)
70'-0" (21336 mm) 2" (51 mm)
80'-0" (24384 mm) 2³⁄₄" (70 mm)
90'-0" (27432 mm) 3¹⁄₂" (89 mm)
100'-0" (30480 mm) 4¹⁄₄" (108 mm)
110'-0" (33528 mm) 5" (127 mm)
120'-0" (36576 mm) 6" (152 mm)
130-0" (39621 mm) 7" (178 mm)
140'-0" (42672 mm) 8" (203 mm)
144'-0" (43890 mm) 8¹⁄₂" (216 mm)
The specifying professional shall give due consideration tocoordinating joist camber with adjacent framing.
103.7 VERIFICATION OF DESIGN AND MANUFACTURE
(a) Design CalculationsCompanies manufacturing any LH- or DLH-SeriesJoists shall submit design data to the Steel JoistInstitute (or an independent agency approved by theSteel Joist Institute) for verification of compliance withthe SJI Specifications.
(d) In-Plant InspectionsEach manufacturer shall verify his ability to manufac-ture LH- and DLH-Series Joists through periodicIn-Plant Inspections. Inspections shall be performed byan independent agency approved by the Steel JoistInstitute. The frequency, manner of inspection, andmanner of reporting shall be determined by the SteelJoist Institute. The plant inspections are not a guaran-ty of the quality of any specific joists; this responsibilitylies fully and solely with the individual manufacturer.
104.1 USAGEThese specifications shall apply to any type of structurewhere floors and roofs are to be supported directly by steeljoists installed as hereinafter specified. Where joists areused other than on simple spans under uniformly distrib-uted loading as prescribed in Section 103.1, they shall beinvestigated and modified if necessary to limit the unitstresses to those listed in Section 103.2.
CAUTION: If a rigid connection of the bottom chord is to bemade to the column or other support, it shall be made onlyafter the application of the dead loads. The joist is then nolonger simply supported, and the system must be investi-gated for continuous frame action by the specifying profes-sional.
The designed detail of a rigid type connection and momentplates shall be shown on the structural drawings by thespecifying professional. The moment plates shall be fur-nished by other than the joist manufacturer.
104.2 SPANThe clear span of a joist shall not exceed 24 times its depth.The term “Span” as used herein is defined as the clearspan plus 8 inches (203mm).
104.3 DEPTHThe nominal depth of pitched chord joists shall be the depthat mid-span. The standard slope of the top chord shall be¹⁄₈ inch per foot (1:96).
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
47
SECTION 104.
APPLICATION
104.4 END SUPPORTS(a) Masonry and Concrete
LH- and DLH-Series Joists supported by masonry orconcrete are to bear on steel bearing plates and shallbe designed as steel bearing. Due consideration of theend reactions and all other vertical and lateral forcesshall be taken by the specifying professional in thedesign of the steel bearing plate and the masonry orconcrete. The ends of LH- and DLH-Series Joists shallextend a distance of not less than 6 inches (152 mm)over the masonry or concrete support and beanchored to the steel bearing plate. The plate shall belocated not more than ¹⁄₂ inch (13 mm) from the face ofthe wall and shall be not less 9 inches (229 mm) wideperpendicular to the length of the joist. It is to bedesigned by the specifying professional in compliancewith the allowable unit stresses in Section A5.1(Allowable Stress Design) of the A.I.S.C. Specification.The steel bearing plate shall be furnished by other thanthe joist manufacturer.
Where it is deemed necessary to bear less than 6inches (152 mm) over the masonry or concrete sup-port, special consideration is to be given to the designof the steel bearing plate and the masonry or concreteby the specifying professional. The joists must bear aminimum 4 inches (102mm) on the steel bearing plate.
(b) SteelDue consideration of the end reactions and all othervertical and lateral forces shall be taken by the speci-fying professional in the design of the steel support.
The ends of LH or DLH-Series Joists shall extend adistance of not less than 4 inches (102mm) over thesteel supports. Where it is deemed necessary to buttopposite joists over a narrow steel support with bear-ing less than that noted above, special ends must bespecified, and such ends shall have positive attach-ment to the support, either by bolting or welding.
104.5 BRIDGING(a) Horizontal
Horizontal bridging lines shall consist of two continu-ous horizontal steel members, one attached to the topchord and the other attached to the bottom chord. Thel/r of the bridging member shall not exceed 300, wherel is the distance in inches (millimeters) between attach-ments and r is the least radius of gyration of the bridg-ing member.
(b) DiagonalDiagonal bridging shall consist of cross-bracing with l/rratio of not more than 200, where l is the distance ininches (millimeters) between connections and r is theleast radius of gyration of the bracing member. Wherecross-bracing members are connected at their point ofintersection, the l distance shall be taken as the
distance in inches (millimeters) between connections at thepoint of intersection of the bracing members and the con-nections to the chord of the joists.
(c) Bridging LinesFor spans up through 60 feet (18288 mm), welded hor-izontal bridging may be used except where the row ofbridging nearest the center is required to be bolteddiagonal bridging as indicated by the Red shadedarea in the load table.
For spans over 60 feet (18288 mm) bolted diagonalbridging shall be used as indicated by the Blue andGray shaded areas of the load table.
(d) SpacingThe maximum spacing of lines of bridging shall notexceed the values in Table 104.5.1. See Section104.12 for bridging required for uplift forces.
(e) ConnectionsConnections to the chords of the steel joists shall bemade by positive mechanical means or by welding,and capable of resisting a horizontal force not less thanthat specified in Table 104.5.1.
(f) Bottom Chord Bearing JoistsWhere bottom chord bearing joists are utilized, thereshall be a row of diagonal bridging near the support toprovide lateral stability. This bridging shall be installedas the joists are set in place.
104.6 INSTALLATION OF BRIDGINGAll bridging and bridging anchors shall be completelyinstalled before construction loads are placed on the joists.
Bridging shall support the top and bottom chords againstlateral movement during the construction period and shallhold the steel joists in the approximate position as shownon the plans.
Table 104.5.1
LH-DLH
*SECTION
NUMBER
MAX. SPACING
OF LINES OF
BRIDGING
HORIZONTAL
BRACING
FORCE
lbs. (N)
02,03,04 11'-0" (3352 mm) 400 (1779)
05,06 12'-0" (3657 mm) 500 (2224)
07,08 13'-0" (3962 mm) 650 (2891)
09,10 14'-0" (4267 mm) 800 (3558)
11,12 16'-0" (4876 mm) 1000 (4448)
13,14 16'-0" (4876 mm) 1200 (5337)
15,16 21'-0" (6400 mm) 1600 (7117)
17 21'-0" (6400 mm) 1800 (8006)
18,19 26'-0" (7924 mm) 2000 (8896)
Number of lines of bridging is based on joist clear span dimensions. *Last two digits of joist designation shown in load table.
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
48
The ends of all bridging lines terminating at walls or beamsshall be anchored to resist the force shown in Table104.5.1.
104.7 END ANCHORAGE(a) Masonry and Concrete
Ends of LH- and DLH-Series Joists resting on steelbearing plates on masonry or structural concrete shallbe attached thereto with a minimum of two ¹⁄₄ inch (6mm) fillet welds 2 inches (51mm) long, or with two ³⁄₄inch (19mm) bolts or the equivalent.
(b) SteelEnds of LH and DLH-Series Joists resting on steelsupports shall be attached thereto with a minimum oftwo ¹⁄₄ inch (6mm) fillet welds 2 inches (51mm) or withtwo ³⁄₄ inch (19mm) bolts or the equivalent. In steelframes, where columns are not framed in at least twodirections with structural steel members, bearing seatsfor joists at column lines shall be fabricated to allow forfield bolting.
(c) UpliftWhere uplift forces are a design consideration, roofjoists shall be anchored to resist such forces.
104.8 JOIST SPACINGJoists shall be spaced so that the loading on each joistdoes not exceed the allowable load given for the particulardesignation and clear span in the Load Table.
104.9 FLOOR AND ROOF DECKS(a) Material
Floor and roof decks may consist of cast-in-place orpre-cast concrete or gypsum, formed steel, wood, orother suitable material capable of supporting therequired load at the specified joist spacing.
(b) ThicknessCast-in-place slabs shall be not less than 2 inches (51mm) thick.
(c) CenteringCentering for structural slabs may be ribbed metal lath,corrugated steel sheets, paper-backed welded wirefabric, removable centering or any other suitable mate-rial capable of supporting the slab at the designatedjoist spacing. Centering shall not cause lateral dis-placement or damage to the top chord of joists duringinstallation or removal of the centering or placing of theconcrete.
(d) BearingSlabs or decks shall bear uniformly along the topchords of the joists.
(e) AttachmentsThe spacing of attachments along the top chord shallnot exceed 36 inches (914 mm). Such attachments ofthe slab or deck to the top chords of joists shall becapable of resisting the following forces:
(f) Wood NailersWhere wood nailers are used, such nailers in conjunc-tion with deck or slab shall be firmly attached to the topchords of the joists in conformance with Section104.9(e).
(g) Joist With Standing Seam RoofingThe stiffness and strength of standing-seam roof clipsvaries from one manufacturer to another. Therefore,some roof systems cannot be counted on to providelateral stability to the joists which support the roof.Sufficient stability must be provided to brace the joistslaterally under the full design load. The compressionchord must resist the chord axial design force in theplane of the joist (i.e., x-x axis buckling) and out of theplane of the joist (i.e., y-y axis buckling). Out of planestrength may be achieved by adjusting the bridgingspacing and/or increasing the compression chordarea, the joist depth, and the y-axis radius of gyration.The effective slenderness ratio in the y-directionequals 0.94 L/ry; where L is the bridging spacing. Themaximum bridging spacing may not exceed that spec-ified in Section 104.5d.
Horizontal bridging members attached to the compres-sion chords and their anchorages must be designedfor a compressive axial force of 0.0025nP, where n isthe number of joists between end anchors and P is thechord design force. The attachment force between thehorizontal bridging member and the compressionchord is 0.005P. Horizontal bridging attached to thetension chords shall be proportioned so that the slen-derness ratio between attachments does not exceed300. Diagonal bridging shall be proportioned so thatthe slenderness ratio between attachments does notexceed 200.
TABLE 104.9.1
*Section Equivalent Number Force Required
02 to 04 incl. 120 lbs./ft. (1.75 kN/m) 05 to 09 incl. 150 lbs./ft. (2.19 kN/m) 10 to 17 incl. 200 lbs./ft. (2.92 kN/m) 18 and 19 250 lbs./ft. (3.65 kN/m)
* Last two digits of joist designation shown in Load Table.
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
49
104.10 DEFLECTIONThe deflection due to the design live load shall not exceedthe following:
Floors: ¹⁄₃₆₀ of span.
Roofs: ¹⁄₃₆₀ of span where a plaster ceiling is attachedor suspended.
¹⁄₂₄₀ of span for all other cases.
The specifying professional shall give due consideration tothe effects of deflection and vibration* in the selection ofJoists.
* For further reference, refer to Steel Joist Institute TechnicalDigest #5, “Vibration of Steel Joist-Concrete Slab Floors”and the Institute’s Computer Vibration Program.
104.11 PONDINGUnless a roof surface is provided with sufficient slopetowards points of free drainage or adequate individualdrains to prevent the accumulation of rain water, the roofsystem shall be investigated to assure stability under pond-ing conditions in accordance with Section K2 (AllowableStress Design) of the AISC Specification.*
The ponding investigation shall be performed by the speci-fying professional.
* For further reference, refer to Steel Joist Institute TechnicalDigest #3, “Structural Design of Steel Joist Roofs to ResistPonding Loads”.
104.12 UPLIFTWhere uplift forces due to wind are a design requirement,these forces must be indicated on the contract drawings interms of net uplift in pounds per square foot (Pascals).When these forces are specified, they must be consideredin the design of joists and/or bridging. A single line of bot-tom chord bridging must be provided near the first bottomchord panel points whenever uplift due to wind forces is adesign consideration.*
* For further reference, refer to Steel Joist Institute TechnicalDigest #6, “Structural Design of Steel Joist Roofs to ResistUplift Loads.”
104.13 INSPECTIONJoists shall be inspected by the manufacturer before ship-ment to insure compliance of materials and workmanshipwith the requirements of these specifications. If the pur-chaser wishes an inspection of the steel joists by someoneother than the manufacturer’s own inspectors, he mayreserve the right to do so in his “Invitation to Bid” or theaccompanying “Job Specifications”.
Arrangements shall be made with the manufacturer forsuch shop inspection of the joists at the manufacturingshop by the purchaser’s inspectors at purchaser’sexpense.
104.14 PARALLEL CHORD SLOPED JOISTSThe Span of a parallel chord sloped joist shall be defined bythe length along the slope. Minimum depth, load-carryingcapacity, and bridging requirements shall be determined bythe sloped definition of span. The Standard Load Tablecapacity shall be the component normal to the joist.
When it is necessary for the erector to climb on the joists,extreme caution must be exercised since unbridged joists mayexhibit some degree of instability under the erector’s weight.
During the construction period, the contractor shall providemeans for adequate distribution of concentrated loads sothat the carrying capacity of any joist is not exceeded.
A) Stability Requirements1) Where the joist span does not exceed the erection
stability span (as indicated by the shaded areas ofthe load table) one end of all joists shall beattached to its support in accordance with Section104.7 – End Anchorage, or the joist shall be stabi-lized by the hoisting cable(s) before allowing theweight of an erector on the joists.
When a bolted seat connection is used for erec-tion purposes, as a minimum, the bolts must besnug tightened. The snug tight condition is definedas the tightness that exists when all plies of a jointare in firm contact. This may be attained by a fewimpacts of an impact wrench or the full effort of anemployee using an ordinary spud wrench.
2) A maximum weight of two erectors shall beallowed on any unbridged joist if: 1) the joist is sta-bilized by the hoisting cable(s), or 2) one end ofthe joist is attached to its support in the mannerprescribed in Section 104.7 - End Anchorage andthe bolted diagonal bridging required for erectionstability is completely installed.
Where the span of the joist exceeds the erectionstability span as indicated by the shaded area ofthe load table, hoisting cables shall not bereleased until the following conditions are met:
a) One line of bolted diagonal bridging iscompletely installed near the mid span forjoist spans included in the Red shaded areaof the load table.
b) Two lines of bolted diagonal bridging near-est the third points of the span are complete-ly installed for spans of over 60 feet(18288mm) through 100 feet (30480mm) asindicated by the Blue shaded area in the LHand DLH Series Joist Load Tables.
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
50
SECTION 105.*
ERECTION STABILITYAND HANDLING
c) All lines of bolted diagonal bridging arecompletely installed for spans over 100 feet(30480 mm) as indicated by the Gray shad-ed area in the DLH Load Table.
3) No loads other than the weight of the erector areallowed on the joist until all bridging is completelyinstalled and all joist ends are attached.
4) In the case of bottom chord bearing joists, theends of the joist must be restrained laterally perSection 104.5(f) before releasing the hoistingcables.
5) After the joist is straightened and plumbed, and allbridging is completely installed and anchored, theends of the joists shall be fully connected to thesupports in accordance with Section 104.7- EndAnchorage.
B) Field Welding1) All field welding shall be performed in a work-
man-like manner to insure that the joists are notdamaged by such welding.
2) On cold-formed members whose yield strengthhas been attained by cold working, and whoseas-formed strength is used in the design, the totallength of weld at any one point shall not exceed 50percent of the overall developed width of thecold-formed section.
C) HandlingParticular attention should be paid to the erection ofLongspan and Deep Longspan Steel Joists. Care shallbe exercised at all times to avoid damage to the joistsand accessories through careless handling duringunloading, storing and erecting.
Each joist shall be adequately braced laterally beforeany loads are applied. If lateral support is provided bybridging, the bridging lines as defined in Section105(A)(2)(a), (b) or (c) must be anchored to preventlateral movement.* For a thorough coverage of this topic, refer to SJI Technical
Digest #9, “Handling and Erection of Steel Joists and JoistGirders”.
LONGSPAN AND DEEP LONGSPAN STEEL JOISTS, LH- AND DLH-SERIES
51
The black figures in the following table give the TOTAL safeuniformly distributed load-carrying capacities, in poundsper linear foot, of LH-Series Steel Joists. The weight ofDEAD loads, including the joists, must in all cases bededucted to determine the LIVE load-carrying capacities ofthe joists. The approximate DEAD load of the joists may bedetermined from the weights per linear foot shown in thetables.
The RED figures in this load table are the LIVE loads perlinear foot of joist which will produce an approximate deflec-tion of ¹⁄₃₆₀ of the span. LIVE loads which will produce adeflection of ¹⁄₂₄₀ of the span may be obtained by multiply-ing the RED figures by 1.5. In no case shall the TOTAL loadcapacity of the joists be exceeded.
This load table applies to joists with either parallel chords orstandard pitched top chords. When top chords are pitched,the carrying capacities are determined by the nominaldepth of the joists at the center of the span. Standard topchord pitch is ¹⁄₈ inch per foot. If pitch exceeds this standard,the load table does not apply. Sloped parallel-chord joistsshall use span as defined by the length along the slope.
Where the joist span is in the RED SHADED area of theload table, the row of bridging nearest the midspan shall bediagonal bridging with bolted connections at chords andintersection. Hoisting cables shall not be released until thisrow of bolted diagonal bridging is completely installed.
Where the joist span is in the BLUE SHADED area of theload table, all rows of bridging shall be diagonal bridgingwith bolted connections at chords and intersection. Hoistingcables shall not be released until the two rows of bridgingnearest the third points are completely installed.
The approximate moment of inertia of the joist, in inches4 is;
I j = 26.767(WLL)(L3)(10-6), where WLL = RED figure in theLoad Table, and L = (clear span + .67) in feet.
When holes are required in top or bottom chords, the car-rying capacities must be reduced in proportion to the reduc-tion of chord areas.
The top chords are considered as being stayed laterally byfloor slab or roof deck.
The approximate joist weights per linear foot shown inthese tables do not include accessories.
52
STANDARD LOAD TABLELONGSPAN STEEL JOISTS, LH-SERIES
Based on a Maximum Allowable Tensile Stress of 30 ksiAdopted by the Steel Joist Institute May 25, 1983;Revised to May 1, 2000 – Effective August 1, 2002
Approx. Wt DepthJoist in Lbs. Per in
Designation Linear Ft inches(Joists only) 25 26 27 28 29 30 31 32 33 34 35 36
* The safe uniform load for the clear spans shown in theSafe Load Column is equal to (Safe Load)/(Clear span +0.67). (The added 0.67 feet (8 inches) is required toobtain the proper length on which the Load Tables weredeveloped).
* In no case shall the safe uniform load, for clear spans lessthan the minimum clear span shown in the Safe LoadColumn, exceed the uniform load calculated for the
minimum clear span listed in the Safe Load Column.
* To solve for live loads for clear spans shown in the SafeLoad Column (or lesser clear spans), multiply the live loadof the shortest clear span shown in the Load Table by the(the shortest clear span shown in the Load Table + 0.67feet)2 and divide by (the actual clear span + 0.67 feet)2.The live load shall not exceed the safe uniform load.
55
The black figures in the following table give the TOTAL safeuniformly distributed load-carrying capacities, in poundsper linear foot, of DLH-Series Steel Joists. The weight ofDEAD loads, including the joists, must in all cases bededucted to determine the LIVE load-carrying capacities ofthe joists. The approximate DEAD load of the joists may bedetermined from the weights per linear foot shown in thetables. All loads shown are for roof construction only.
The RED figures in this load table are the LIVE loads perlinear foot of joist which will produce an approximate deflec-tion of ¹⁄₃₆₀ of the span. LIVE loads which will produce adeflection of ¹⁄₂₄₀ of the span may be obtained by multiply-ing the RED figures by 1.5. In no case shall the TOTAL loadcapacity of the joists be exceeded.
This load table applies to joists with either parallel chords orstandard pitched top chords. When top chords are pitched,the carrying capacities are determined by the nominaldepth of the joists at the center of the span. Standard topchord pitch is ¹⁄₈ inch per foot. If pitch exceeds this standard,the load table does not apply. Sloped parallel-chord joistsshall use span as defined by the length along the slope.
All rows of bridging shall be diagonal bridging with boltedconnections at the chords and intersections.
Where the joist span is in the BLUE SHADED area of theload table hoisting cables shall not be released until the tworows of bridging nearest the third points are completelyinstalled.
Where the joist span is in the GRAY SHADED area of theload table hoisting cables shall not be released until all rowsof bridging are completely installed.
The approximate moment of inertia of the joist, in inches4 is;
I j = 26.767(WLL)(L3)(10-6), where WLL = RED figure in theLoad Table, and L = (clear span + .67) in feet.
When holes are required in top or bottom chords, the car-rying capacities must be reduced in proportion to the reduc-tion of chord areas.
The top chords are considered as being stayed laterally byfloor slab or roof deck.
The approximate joist weights per linear foot shown inthese tables do not include accessories.
STANDARD LOAD TABLEDEEP LONGSPAN STEEL JOISTS, DLH-SERIES
Based on a Maximum Allowable Tensile Stress of 30 ksiAdopted by the Steel Joist Institute May 25, 1983;Revised to May 1, 2000 – Effective August 1, 2002
* The safe uniform load for the clear spans shown in theSafe Load Column is equal to (Safe Load)/(Clear span +0.67). (The added 0.67 feet (8 inches) is required toobtain the proper length on which the Load Tables weredeveloped).
* In no case shall the safe uniform load, for clear spans lessthan the minimum clear span shown in the Safe LoadColumn, exceed the uniform load calculated for the
minimum clear span listed in the Safe Load Column.
* To solve for live loads for clear spans shown in the SafeLoad Column (or lesser clear spans), multiply the live loadof the shortest clear span shown in the Load Table by (theshortest clear span shown in the Load Table + 0.67 feet)2
and divide by (the actual clear span + 0.67 feet)2 . The liveload shall not exceed the safe uniform load.
57
The black figures in the following table give the TOTAL safeuniformly distributed load-carrying capacities, inkiloNewtons per meter (kN/m) of LH-Series Steel Joists.The weight (kN/m) of the DEAD loads, including the joists,must in all cases be deducted to determine the LIVEload-carrying capacities of the joists. The approximateDEAD load of the joist may be determined from the weightsshown in the tables.
The RED figures this load table are the LIVE loads(kiloNewtons per meter) of joist which will produce anapproximate deflection of ¹⁄₃₆₀ of the span. LIVE loads whichproduce a deflection of ¹⁄₂₄₀ of the span may be obtained bymultiplying the red figures by 1.5. In no case shall theTOTAL load capacity of the joists be exceeded.
This load table applies to joists with either parallel chords orstandard pitched top chords. When top chords are pitched,the carrying capacities are determined by the nominaldepth of the joist at center of the span. Standard top chordpitch is 1:96. If pitch exceeds this standard, the load tabledoes not apply. Sloped parallel-chord joists shall use spanas defined by the length along the slope.
Where the joist span is in the RED SHADED area of theload table, the row of bridging nearest the mid span shall bediagonal bridging with bolted connections at chords andintersection. Hoisting cables shall not be released until thisrow of bolted diagonal bridging is completely installed.
Where the joist span is in the BLUE SHADED area of theload table, all rows of bridging shall be diagonal bridgingwith bolted connections at chords and intersection. Hoistingcables shall not be released until the two rows of bridgingnearest the third points are completely installed.
When holes are required in top or bottom chords, the car-rying capacities must be reduced in proportion to the reduc-tion of chord areas.
The top chords are considered as being stayed laterally byfloor slab or roof deck.
The approximate joist weights (kg/m) and mass (kN/m)shown in these tables do not include accessories.
The approximate moment of inertia of the joist, in mm4 is:
I j = 2.6953(WLL)(L3)(10-5), where WLL = RED figure in theLoad Table: L = (span + 204) in millimeters.
METRIC LOAD TABLELONGSPAN STEEL JOISTS, LH-SERIES
Based on a Maximum Allowable Tensile Stress of 207 MPaAdopted by the Steel Joist Institute May 2, 1994;
Revised to May 1, 2000 – Effective August 1, 2002
Joist Approx Approx DepthDesignation Mass Mass (mm) CLEAR SPAN (mm)
* The safe uniform load for the clear spans shown in theSafe Load Column is equal to (Safe Load)/(Clear span +204). (The added 204 millimeters is required to obtain theproper length on which the Load Tables were developed).
* In no case shall the safe uniform load, for clear spans lessthan the minimum clear span shown in the Safe LoadColumn, exceed the uniform load calculated for the mini-mum clear span listed in the Safe Load Column.
* To solve for live loads for clear spans shown in the SafeLoad Column (or lesser clear spans), multiply the live loadof the shortest clear span shown in the Load Table by the(the shortest clear span shown in the Load Table + 204mm)2 and divide by (the actual clear span + 204 mm)2.The live load shall not exceed the safe uniform load.
60
The black figures in the following table give the TOTAL safeuniformly distributed load-carrying capacities, inkiloNewtons per meter (kN/m) of DLH-Series Steel Joists.The weight (kN/m) of the DEAD loads, including the joists,must in all cases be deducted to determine the LIVEload-carrying capacities of the joists. The approximateDEAD load of the joist may be determined from the weightsshown in the tables. All loads shown are for roof construc-tion only.
The RED figures this load table are the LIVE loads(kiloNewtons per meter) of joist which will produce anapproximate deflection of ¹⁄₃₆₀ of the span. LIVE loads whichproduce a deflection of ¹⁄₂₄₀ of the span may be obtained bymultiplying the RED figures by 1.5. In no case shall theTOTAL load capacity of the joists be exceeded.
This load table applies to joists with either parallel chords orstandard pitched top chords. When top chords are pitched,the carrying capacities are determined by the nominaldepth of the joist at center of the span. Standard top chordpitch is 1:96. If pitch exceeds this standard, the load tabledoes not apply. Sloped parallel-chord joists shall use spanas defined by the length along the slope.
All rows of bridging shall be diagonal bridging with boltedconnections at the chords and intersections.
Where the joist span is in the BLUE SHADED area of theload table hoisting cables shall not be released until the tworows of bridging nearest the third points are completelyinstalled.
Where the joist span is in the GRAY SHADED area ofthe load table hoisting cables shall not be released until allrows of bridging are completely installed.
When holes are required in top or bottom chords, the car-rying capacities must be reduced in proportion to the reduc-tion of chord areas.
The top chords are considered as being stayed laterally bythe roof deck.
The approximate joist weights (kN/m) and mass (kg/m)shown in these tables do not include accessories.
The approximate moment of inertia of the joist, in mm4 is:
I j = 2.6953(WLL)(L3)10-5), where WLL = RED figure in theLoad Table; L = (span + 204) in millimeters.
* The safe uniform load for the clear spans shown in theSafe Load Column is equal to (Safe Load)/(Clear span +204). (The added 204 millimeters is required to obtain theproper length on which the Load Tables were developed).
* In no case shall the safe uniform load, for clear spans lessthan the minimum clear span shown in the Safe LoadColumn, exceed the uniform load calculated for the mini-mum clear span listed in the Safe Load Column.
* To solve for live loads for clear spans shown in the SafeLoad Column (or lesser clear spans), multiply the live loadof the shortest clear span shown in the Load Table by the(the shortest clear span shown in the Load Table + 204mm)2 and divide by (the actual clear span + 204 mm)2 .The live load shall not exceed the safe uniform load.
