Department of Construction
Subject: Temporary Works
Quiz 1 13/14
Higher Diploma in Civil Engineering (EG114101) - Restudy
Time Allowed : 90 minutes
Instruction: Answer ALL questions.
Q.1 A proposed timber soffit form is designed for casting a 500 mm thick concrete slab which measures 4.5 m by 15 m on plan. The detailed layout of the soffit form is shown in Fig. Q1. The formwork is supported by rows of secondary timber bearers spaced at 300 mm center to center (c/c), which rest on 4 rows of primary bearers spaced at 1500 mm c/c. The latter are in turn supported by vertical props spaced at 1500 mm c/c. The loading information, design criteria and the mechanical properties of the formwork materials are as follows:
Loading Information
Unit Concrete Weight 25 kN/m3
Operation Load 2.0 kN/m2
Design Criteria
Deflection of any component not to exceed of Span
Mehcanical Properties of Formwork Components
Formwork Materials / Permissible Moment of Resistance / Permissible Shear Load / StiffnessEI
19 mm thick
Plywood Sheeting
(per m width) / 0.420 kN-m /m / 7.86 kN /m / 3.50 kN-m2 /m
75x100 Secondary Timber Bearers each 4.5 metres long / 2.500 kN-m / 11.80 kN / 149.14 kN-m2
100x225 Primary Bearers each 15 metres long / 10.39 kN-m / 63.21 kN / 839.58 kN-m2
Given the equations on Page 5, check the adequacy of the specified spacing of the individual components in the proposed formwork.
(50 marks)
Q.2 Fig. Q2 shows the layout of a formwork for a 1600x1600 square column. The formwork consists of an internal plywood sheeting lining supported around its periphery by vertical studs each 1.35 m long at 200 mm center to centre. The internal design concrete pressure of 85 kN/m2 is resisted by two opposite walers at 2200 mm apart which are in turn tied together at their ends with a pair of steel tie rods. The horizontal walers spacing is 450 mm center to center. Using the formulae on Page 5 and given the following design loading/criteria information and formwork material properties:
Design Loading/Criteria
Concrete pressure 85 kN/m2
Deflection 1/270 of span of each formwork
Component.
Material Properties
Formwork Materials / Permissible Moment of Resistance / Permissible Shear Load / StiffnessEI
Plywood Sheeting
(per m width) / 0.420 kN-m /m / 11.86 kN /m / 3.50 kN-m2 /m
Vertical Studs / 2.500 kN-m / 11.80 kN / 149.14 kN-m2
Horizontal waler / 30.39 kN-m / 130.21 kN / 2539.58 kN-m2
Check the adequacy of the formwork layout. If any component of the layout is found unsatisfactory, suggest improvement measure(s).
(50 marks)
A
19 mm thick Plywood Sheeting
Secondary Timber Bearers spaced at 300 mm
Overall Length 15 m
A
1500 1500
Typical Layout of Soffit Form
4500
TTt
U-Head Jack
Prop
1500 1500 1500
SECTION A-A
Fig. Q1
(Not to Scale)
1600
Plywood sheeting
Column Form 1600
V vertical studs at 200 c/c
Horizontal walers at 450 c/c
2200
Ties
Fig. Q2 (Not to Scale)
Formulas
Continuous Beam for more than 3 spans
w
Max. Bending Moment= 0.107wL2
Max. Shear = 0.607wL L L L L
Max. Deflection =
3-span Continuous Beam
w
Max. Bending Moment= 0.100wL2
Max. Shear = 0.600wL L L L
Max. Deflection =
Max. Support Reaction = 1.1 wL
Single-span Simply Supported Beam (Symmetrically loaded)
Assume X is close to L:
Max. Bending Moment= L
w
Max. Shear = 0.5wL
X
Max. Deflection @@
Where w = Uniformly Distributed Load
X = Span
L = Loaded Length
EI = Stiffness of Beam
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