FORMWORK

Prof Awad S. Hanna

FormworkForms are molds to receive concrete in its plastic form.Formwork is temporary structure, as such, it is not normally shown on the drawings.

Prof Awad S. Hanna

Formwork for Beams and Slabs

Prof Awad S. Hanna

Formwork MaterialsWoodEither all-wood or some wood componentsPlywoodAluminumSteelPlastics

Prof Awad S. Hanna

LumberDesignated by Cross Sections, Nominal Dimensions (prior to finishing)After cut length wise, finishing operations reduces actual dimensions2 x 4 Plank1 1/2 x 3 1/2 2 by 4 in S4SLengths are multiples of 2 ft (8, 10, 12, 14, 16,)Specified by type and gradeType: pine, oak, firGrade: Selected (A, B, C, D) and Common (1, 2, 3, 4)Selected (A best, D poor quality)Cost Kind, grade, size, length, milling, quantity, freight

Prof Awad S. Hanna

Plywood4 ft wide - 8, 10, 12 ft long1/4, 3/8, 1/2, 5/8, 3/4 inch thick

Prof Awad S. Hanna

Plywood OrientationFace Grain DirectionFace Grain DirectionWeak Orientation of Plywood(Face grain parallel to span)Strong Orientation of Plywood(Face grain perpendicular to span)

Prof Awad S. Hanna

AluminumPure aluminum chemically attacked by wet concreteLight weight allow larger forming unitsHigh reuse valueAluminum beamnailer - type

Prof Awad S. Hanna

SteelFor heavy concrete workWith reasonable care will last indefinitelyHigh initial cost and high handling cost

Prof Awad S. Hanna

Estimating IssuesNormally, the forms are used more than onceMore usage of forms reduce the priceWood forms have less usage potential than aluminum or steel formsComplicated shapes of concrete are more expensive because of labor cost and reuse of forms.

Prof Awad S. Hanna

Estimating Issues (cont.)Majority of cost is _____?? Not ____??You have to have a construction plan to determine the reuse cycleNumber of reused largely controls _____?? Cost.

Prof Awad S. Hanna

Effect of Reuse on Concrete Formwork Cost

Prof Awad S. Hanna

Sheet1

Number of usesCost per square foot of contact area

11.00

20.62

30.50

40.44

50.40

60.37

70.36

90.32

Sheet2

Sheet3

Estimating Issues (Formwork)Do not deductIntersection of beamsIntersection of beams & columns & wallsAny opening < 100 sq. ft.

Prof Awad S. Hanna

FormworkUnit of MeasurementSquare Foot Contact AreaSFCAMeasure just contact area, not area of formworkContact Area= 2h(L+B)ConcreteLBh

Prof Awad S. Hanna

Wood normally measured:Linear feet of one sizeBoard FeetFBM (Foot Board Measure)1x12x1(long) or 144 cubic inchesexample: 2x8 x 16ft long = 1.33 BF/LF x 16 = 21.28 FBM2 x 812

Prof Awad S. Hanna

Additional CostsNailsFor first use, 10 - 20 lb. Per 1000 fbmAdditional used, 5 - 10 lb. Per fbmForm Oil300 - 500 ft2/galTiesTies keep forms apart and resist bursting pressure of concreteStay in concrete, pull outTypes:Steel bandsRodsThreadedw/ Nuts and clamps

Prof Awad S. Hanna

Design and Estimating of FormsDesign determine Sheathing thickness, stud size, wale size, tie sizeUse of design tablesWatch for1.Rate of pour2.Temperature and weather3.Proportions of mix and consistency4.Method of placement and vibration

Prof Awad S. Hanna

Workshop ExampleEstimate the cost of formwork for concrete wall (96 x 254)The rate of placing concrete = 4 ft/hourMaximum temperature of concrete = 70F

Prof Awad S. Hanna

Concrete Footing96Wall tie3/4 plywood sheathing2x 4x 10- 0 stud2- 2x 4wale2x 4 x 10- 0brace @ 6- 02x 4 sill254Side ElevationSection through the Wall2x 4x 3- 0Stake @ 6- 0

Prof Awad S. Hanna

Design of Forms for concrete Walls

Prof Awad S. Hanna

Sheet1

Minimum Temperature of concrete, F507090

Rating of filling forms, ft/h246246246

Maximum pressure, lb/ft25108701230409664921350550750

Maximum spacing of studs for safe value of sheathing, in

For 1- in sheathing221714241916262118

For 2- in sheathing382924423328453631

Maximum spacing of wales for safe value of studs, in

2 x 4 studs 1- in sheathing262321282523292624

4 x 4 studs 1- in sheathing403533433835454037

2 x 6 studs 1- in sheathing413633443936464138

2 x 6 studs 2- in sheathing312725332927353129

4 x 4 studs 2- in sheathing312725332927343028

3 x 6 studs 2- in sheathing413633433835454137

Maximum spacing of form ties for safe values of wales, in

Double 2 x 4 wales 2 x 4 stud 1S342824373127393329

Double 2 x 4 wales 4 x 4 stud 1S302421322724342926

Double 2 x 4 wales 2 x 6 stud 1S27220292422312623

Double 2 x 6 wales 2 x 6 stud 1S433531463834494137

Double 2 x 6 wales 3 x 6 stud 1S433531483935504137

Sheet2

Sheet3

44488889-625- 4

Prof Awad S. Hanna

The wall is 9-6 high and 25-4 long.From design table:Max. pressure, 664 lb/ft2Max. spacing of studs, 19 in, use 18 inMax. spacing of wales, 25 in, use 24 inMax. spacing of form ties, 31 inThe 3/4 plywood sheathing will be placed with the 4 ft wide in the vertical direction and the 8 ft length in the horizontal direction.The total quantity of sheathing will be:No. sheets in vertical direction, 9-6 4/sheet = 2.37, use 3 sheetsNo. sheets in horizontal direction, 25-4 8/sheet = 3.16, use 4 sheetsNo. sheets required per side, 3 x 4 = 12No. sheets required for wall, 12 x 2 = 24

Prof Awad S. Hanna

Studs required:Length of wall, (25 x 12)+4= 304 inSpacing of studs, 18 inNo. studs required per side, (304/18)+1= 18No. studs required for wall, 2 x18= 26Lumber required, 36 pc, 2 x4 x 10 ft= 240 fbmWales required:Height of wall, 114 inSpacing of wales, 24 inNo. required per side, 114/24= 4.75, use 5 walesFor each wale, use 2 pc of 2x4 x 12 ftand 2 pc of 2x4 x 14 ft lumberLumber required:20 pc, 2x4 x 12 ft = 160 fbm20 pc, 2x4 x 14 ft = 187 fbm

Prof Awad S. Hanna

Total lumber = 240 + 160 +187= 587 fbmAdd 10 to 20% for misc. (sills, spliceetc)

Total quantity of lumber= 587 + 0.2 x 587= 704 fbm

Prof Awad S. Hanna

Number of ties neededIf we use 4000 lb tiesNumber of ties == 51ties644 x 9.5 x 25.34000

Prof Awad S. Hanna

Quantity of Nails= 704 x 10 lb/1000fbm= 7.04 lbs

Prof Awad S. Hanna

Summary of Materials to Build forms:Plywood required= 24 sheetsLumber required= 704 fbmNails required= 7 lbsTies required= 51

Prof Awad S. Hanna