Academic Year 2007/08 - VTCtycnw01.vtc.edu.hk/cbe3033/Past Exam Papers with... · Web view(Ans....

PAST EXAMINATION PAPERS – Numerical Problems with AnswersMODULE: - TEMPORARY WORKS

Academic Year 2007/08Q.1 Fig. Q1 shows a 7.4 m tall cantilever formwork designed for

casting successive lifts of concrete 4 m each in height. The formwork has a steel truss strongback behind the plywood sheeting and is anchored by three rows of anchor bolts at 1.0 m vertically apart as shown in the figure. It weighs 20 kN per longitudinal metre run. The horizontal spacing for each row of anchor bolts is 0.5 m center to center. Anticipated site conditions during concreting operation will be as follows:

Concrete temperature 5 – 32CUnit weight of concrete 25 kN/m3

Rate of concrete delivery Each 4-m lift will be completed in 8 hours.

(a) Given the following formula in computing concrete pressure acting on formwork, determine the design concrete pressure in kPa for the 4-m LIFT and draw the concrete pressure distribution diagram accordingly.

Hint: in kPa, or

(6 marks)(Ans. 77.67 kPa)

(b) Among the three horizontal rows of anchor bolts, it is assumed that the middle bolts are installed for additional safety only and will not offer any tension nor compressive forces under normal design condition. Calculate the tension in each upper anchor bolt in kN for the formwork having a safety factor of 1.2 against overturning about its lower row of anchor bolts.

(12 marks)(Ans. 255.025 kN)

(c) Calculate the tension in each anchor bolt in the middle row if all the anchor bolts of the uppermost row fail in pull-out mode.

(4 marks)


(Ans. 510.049 kN)

(d) State the general considerations in structural design of falsework(3 marks)

Q.2 Fig. Q2 shows the elevation layout of a typical transverse row of a birdcage scaffold structure measured 8.4 m (H) and 9.1 m (W). There are 12 rows of falsework framework in longitudinal direction each comprising of mild steel tubing and fittings all complying with BS1139. The falsework will be erected to support the construction of a concrete slab.

Given the following configuration of the falsework and design loading information:

Design LoadingConcrete slab thickness 150 mmOperation load 2.0 kPaSelf weight of Formwork & Scaffolding

1.0 kPa

Design wind speed 40 m/s

Falsework ConfigurationLift Height 1.4 m

Bay Length 1.30 m c/c in transverse

direction 1.35 m c/c in longitudinal

directionSolidity Ratio of scaffolding exposed to transverse wind:

5%

(a) Determine the total wind moment acting on the falsework structure. Assume that the dynamic wind pressure q (in KPa) for wind speed Vd (in m/s) is given by and pressure coefficient Cf = 1.3 and 2.0 for circular scaffolding tubing and the edge form respectively. (5 marks)

(Ans. 27.643 kN-m per row)


(b) Determine the total leg load in kN in each individual verticals (standards) of the scaffold under the combined vertical and horizontal loading condition. Using the Table Q2 to check the axial loading capacity of the verticals against lateral buckling. Identify if there are any verticals under tension. Assume scaffolding tubes of “USED” condition will be used.

(13 marks)

(Ans.13.11 kN; None of the Verticals are under Tension)

(c) Determine the minimum number of diagonal braces required to resist the horizontal wind load. Draw the layout of the diagonal braces provided for the falsework.

(4 marks)

(Ans. Two (2) Diagonal Braces per row)

(d) Determine the safety factor against overturning for the falsework when the soffit formwork is standing EMPTY but with operation load and calculate the kentledge required, if required, to meet the minimum safety factor of 1.2

(3 marks)

(Ans. 6.07; No Kentledge is req’d)

Hint: Formulas for calculating leg loads induced by overturning moment M are given as follows:

Q.3 A large panel of soffit formwork is designed for the construction of a 250 mm thick concrete deck slab.

Determine the maximum spacing of the formwork components given the following design and formwork material information are used.

Design Information


Unit weight of concrete - 25 kN/m3

Construction operation load – 2.0 kN/m2

Deflection not to exceed 1/360 of span

Formwork Material Information

Formwork Materials Permissible Moment of Resistance

Permissible Shear Load

StiffnessEI

Plywood Sheeting 0.420 kN-m /m 7.86 kN /m 3.50 kN-m2 /m

Timber Bearers each 3 metres long

1.00 kN-m 6.80 kN 79.14 kN-m2

Steel Joists supported by vertical props

5.39 kN-m 30.21 kN 100.58 kN-m2

Hint: Assume all formwork components are continuous beams of multiple equal spans and the following formulas to be used.

Max. Bending Moment for a continuous beam under UDL

Max. Shear Force

Max. Deflection = 0.007 for plywood; and

= 0.004 for bearers and steel joists,

where ω = Uniformly Distributed Load (UDL) on span L (kN per metre run)

(25 marks)

(Ans. Timber Bearer - 0.550 m c/c; Steel Joist - 1.475 m c/c; Prop - 1.75 m c/c)


Q.4 A propped cantilever steel sheet piling cofferdam is designed to resist a 6 m (H) high vertical cut as detailed in Fig. Q4. Given the following soil properties and loading information :

Active earth pressure coefficient Ka 0.30Passive earth pressure coefficient Kp 2.85Unit weight of soil 18 kN/m3

Surcharge Load 20 kN/m2

and the net earth pressure diagram shown in the figure, use the FREE EARTH SUPPORT method to determine the:

(i) Depth of point of zero net earth pressure (Z);(4 marks)

(Ans. 0.84 m)(ii) Prop load if the props are spaced to leave a working

clearance of 3.0 m on plan for equipment passing between the ground level and the bottom of excavation;

(12 marks)(Ans. 248.81 kN)

(iii) Minimum depth of embedment (D) that the pile has to be driven if the factor of safety for moment equilibrium is designed to be not less than 2.0. (Hint start D=X+Z = 2.8 m for iterations).

(5 marks)(Ans.3.16 m)

(iv) Suggest with illustration alternative design provision if there are existing underground utilities which obstruct the depth of piling to be driven as obtained in (iii)

(4 marks)


Academic Year 2006/07Q.1 Fig. Q1 shows the elevation layout of a typical transverse row of

a birdcage scaffold structure measured 7.8 m (H) and 8.4 m (W). The framework consists of mild steel tubing and fittings all complying with BS1139. The longitudinal spacing of scaffold is at 1.35 m center to center. It is designed to support an elevated working platform with an operation load of 1.5 kPa. The combined selfweight of the falsework and platform is 1.0 kN per m2 of plan area. The design transverse wind speed Vd in the vicinity of the structure is 20 m/s. Assume the platform structure is equipped with a toe board 0.2 m high along its free edges at the roof level.

(e) Verify that the total wind moment acting on the whole scaffold structure is 8.37 kN-m per row. Assume that the dynamic wind pressure is given by (Vd in ms-1

and q in kPa) and pressure coefficient Cf = 1.3 and 2.0 for circular scaffolding tubing and the edge toeboard respectively. Assume that the solidity ratio of the scaffold area exposed to the transverse wind is 6%.

(5 marks)

(Ans. 8.371 kN-m per row)

(f) Determine the total leg load in kN in each individual verticals (standards) of the scaffold under the combined vertical and wind loading condition. Using Table Q1, check the axial loading capacity of the verticals against lateral buckling if they are all of “Used” condition. Identify if there are any verticals under tension.

(10 marks)

(Ans. 4.47 kN, None of Verticals are under tension)

(g) Determine the minimum number of diagonal braces required to resist the horizontal wind load. Draw the layout of the diagonal braces provided for the scaffold structure.


(7 marks)

(Ans. One (1) Diagonal Brace per row)

(h) Determine the safety factor against overturning for the scaffold structure if there is no construction activity on the platform and calculate the kentledge required if it is less than 1.2.

(3 marks)(Ans. 5.69 No Kentledge is required)

Q.2 A formwork is proposed for concreting a 800x800 square column. The design internal concrete pressure of 90 kN/m2 is to be resisted by the components given in the table as shown underneath. Using the formulae on and the following design loading/criteria information and formwork material properties:

(a) Calculate the maximum spacing of individual formwork components to the nearest 25 mm;

(20 marks)(b) Prepare the typical column formwork layout.

(5 marks)Design Loading/CriteriaConcrete pressure 90 kN/m2

Deflection 1/360 of span of each formworkcomponent.

Material Properties



StiffnessEI

Plywood Sheeting(per m width) 0.420 kN-m /m 9.952 kN /m 3.50 kN-m2 /m

Vertical 50x225 Timber Studs each 2.5 2.500 kN-m 8.93 kN 73.00 kN-m2


m longHorizontal 50x127 RSJ Waler 12.057 kN-m 50.67 kN 496.44 kN-m2

(Ans. Vertical Stud – 0.175 m c/c; Horizontal Waler – 0.925 m c/c; Toe Rod – 1.025 m c/c)

Q.4 The 5 metres high single skin cantilever wall form detailed in Fig. Q4 is designed to receive concrete mix from its top in one go. The rate of vertical rise of concrete level will reduce gradually from 450 mm per hour at the bottom to 150 mm per hour at the top of the wall form throughout the concrete filling process.

Anticipated site conditions during concreting will be as follows:Concrete temperature 10 – 35CUnit weight of concrete 25 kN/m3

(a) Given the following formula in computing concrete pressure acting on formwork, determine the design concrete pressure in kPa for the form in every 1-m intervals and hence plot its variation along the height of the form.

in kPa, or

(20 marks)

(Ans.

Depth Rate of RisePmax by

FormulaHydrostatic

D*hDesign

Pressure

Elev. above

bottomh R 　　　　m m/h kN/m2 kN/m2 kN/m2 m

0.00 0.150 56.00 0.00 0.00 5.00


1.00 0.210 57.42 25.00 25.00 4.00 2.00 0.270 58.64 50.00 50.00 3.00 3.00 0.330 59.73 75.00 59.73 2.00 4.00 0.390 60.73 100.00 60.73 1.00 5.00 0.450 61.65 125.00 61.65 0.00

(b) Assume the maximum concrete pressure Pmax calculated from part (a) is UNIFORMLY ACTING on the full height of the wall form and there are two parallel rows of external raking struts erected at a horizontal spacing of 0.8 m centre to centre to support the concrete pressure thrust as shown in the Fig. Q4. If a minimum factor of safety of 1.5 against strut failure is to be adopted, what is the design axial load in each individual strut assuming that they are all equally loaded ?

(5 marks)(Ans. 261.54 kN)

Q.6 A single-propped cantilever steel sheet piling cofferdam is designed to resist a 4.5 m high vertical cut as shown in Fig.Q6. Given the following soil properties and design information:

Height of soil to be retained 4.5mDepth of the prop below ground level 0.6 mHorizontal spacing of props 3 mActive Earth Pressure Coefficient Ka 0.25Passive Earth Pressure Coefficient Kp 2.00Unit weight of soil 17 kN/m3

Surcharge Load 20kN/m2

Use FREE EARTH SUPPORT METHOD to determine the:(i) Depth of point of zero net earth pressure Z (4 marks)

(Ans. 0.811 m)

(ii) Determine the strut load (12 marks)


(Ans. 132.12 kN)

(iii) Minimum depth of embedment D that the pile has to be driven.

(Ans. 2.81 m )

(9 marks)

(Hint: Try the depth below point of zero net earth pressure X = 1.0 m for the first iteration )


Academic Year 2005/06Q.1 An illegally constructed concrete slab measuring 6 m long and

1.2 m wide and of thickness 250 mm standing 2.6 m above a footpath was found defective and ordered to be removed by the Buildings Department. A contractor is subsequently called upon to remove the slab while the pedestrian traffic underneath has to be maintained. For executing the demolition work, the Contractor proposes to use steel beams at the ceiling which in turn are supported by a shore structure assembled from BS 1139 steel scaffolding tubing and fittings to protect pedestrians under the ceiling as shown in Fig.Q1. Given the following design information:

Imposed load 2.0 kPaSteel Beam 1.5 kPaSelf weight of Scaffolding Frame 0.5 kPaUnit weight of Concrete 24 kN/m3

Lateral Load designed to be 2.5% of total vertical load applied at the ceiling level

(i) Verify that the overturning moment acting on a typical interior transverse row of shore structure above the footpath level is 1.17 kN-m;

(5 marks)(Ans. 1.17 kN-m per row)

(ii) Use the overturning moment of 1.17 kN-m to calculate the maximum scaffold leg load and check its structural adequacy from Table Q1; (Assume scaffolding is of “USED” condition)


(iii) Determine the factor of safety against overturning for the typical transverse row;

(5 marks)(Ans. 9.23)

(iv) Determine the number of diagonal bracing required for the longitudinal stability of the scaffold shore structure


and draw the layout arrangement. Assume couplers of 6.5 kN capacity each are used to fix diagonal braces.

(10 marks)(Ans. One (1) Longitudinal Diagonal Brace)

Q.2 Fig. Q2 shows the layout of a formwork for a 1000x1000 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 centre to centre. The internal design concrete pressure of 80 kN/m2 is resisted by two opposite walers at 1400 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 centre to centre. Use the formulae on Page 7 and the following design loading/criteria information and formwork material properties to check the adequacy of the formwork layout. If any component of the layout is found unsatisfactory, suggest improvement measure(s).

Design Loading/CriteriaConcrete pressure 80 kN/m2

Deflection 1/270 of span of each formworkcomponent.

Material Properties



StiffnessEI

Plywood Sheeting(per m width) 0.420 kN-m /m 9.952 kN /m 3.50 kN-m2 /m

Vertical Studs 2.500 kN-m 8.93 kN 73.00 kN-m2

Horizontal waler7.057 kN-m 20.67 kN 396.44 kN-m2

(25 marks)


(Ans. Vertical Stud – 0.2 m c/c; Horizontal Waler – 0.45 m c/c; Tie Rod – 1.4 m c/c)

Q.4 The 15 metres high prismatic pier form detailed in Fig. Q4 consists of two parts. The 3 m high upper part tapers from 7 m x 7 m square section at the top to 5 m x 5m square section at elevation X-X while the lower 12 m tall column further tapers down to 2.5 m x 2.5 m square section. Concrete will be cast in one goal by placing concrete from the top.

Anticipated site conditions during concreting will be as follows:Concrete temperature 15 – 32CUnit weight of concrete 25 kN/m3

Rate of concrete delivery 24 m3 per hour

(a) Given the following formula in computing concrete pressure acting on formwork, determine the design concrete pressure in kPa for the form in every 1-m intervals and hence plot its variation along the height of the form.

in kPa, or

(20 marks)

DepthSide

LengthPlan Area Rate of Rise

Pmax by Formula

Hydrostatic D*h

Design Pressure

h D A=D^2-Void R 　　　m m m2 m/h kN/m2 kN/m2 kN/m2

0.00 7.000 49.000 0.490 82.91 0.00 0.00 1.00 6.333 36.111 0.665 86.89 25.00 25.00 2.00 5.667 31.111 0.771 89.06 50.00 50.00 3.00 5.000 25.000 0.960 92.55 75.00 75.00 4.00 4.792 22.960 1.045 94.01 100.00 94.01 5.00 4.583 21.007 1.142 95.61 125.00 95.61


6.00 4.375 19.141 1.254 97.36 150.00 97.36 7.00 4.167 17.361 1.382 99.29 175.00 99.29 8.00 3.958 15.668 1.532 101.41 200.00 101.41 9.00 3.750 14.063 1.707 103.78 225.00 103.78

10.00 3.542 12.543 1.913 106.42 250.00 106.42 11.00 3.333 11.111 2.160 109.38 275.00 109.38 12.00 3.125 9.766 2.458 112.75 300.00 112.75 13.00 2.917 8.507 2.821 116.59 325.00 116.59 14.00 2.708 7.335 3.272 121.01 350.00 121.01 15.00 2.500 6.250 3.840 126.17 375.00 126.17

(b) A design horizontal force of 10 kN acts at an elevation of 11.25 m above the bottom of the form. Neglect the light self weight of the formwork and calculate the minimum strut load in kN in each raking strut which inclines at 60 to the horizontal as shown in Fig.Q4 so that a minimum factor of safety against overturning of 1.2 can be achieved for the lateral stability of the whole formwork.


Q.6 A single-propped cantilever steel sheet piling cofferdam is designed to resist a 7.5 m high vertical cut as shown in Fig.Q6. Given the following soil properties and design information:

Height of soil to be retained 7.5mDepth of the prop below ground level 0.9 mHorizontal spacing of props 3.5 mActive Earth Pressure Coefficient Ka 0.25Passive Earth Pressure Coefficient Kp 2.00Unit weight of soil 17 kN/m3

Surcharge Load 20kN/m2

Use FREE EARTH SUPPORT METHOD to determine the:

(i) Depth of point of zero net earth pressure Z (4 marks)


(Ans. 1.239 m)

(ii) Determine the strut load (12 marks)

(Ans. 348.17 kN)

(iii) Minimum depth of embedment D that the pile has to be driven.

(Hint: Try the depth below point of zero net earth pressure X = 1.75 m for the first iteration )

(9 marks)

(Ans. 4.44 m )


HONG KONG INSTITUTE OF VOCATIONAL EDUCATION (TSING YI)

Department of Construction

2008/09 Sessional Examination (Spring Semester)

Course Name (Code) : Higher Diploma in Civil Engineering (51301F) Higher Diploma in Civil Engineering (51301A)

Level/Year of Study : Level 4 (51301F)

Year 2 (51301A)

Mode of Study : FT

Unit : Temporary Works (CBE3033)

Date : 10 June 2009

Time : 1:30 p.m. – 4:30 p.m.

Time Allowed : THREE (3) Hours

Instructions to Candidates:

1. Answer ANY FOUR (4) questions2. All questions carry EQUAL marks.3. This question paper has N INE ( 9 ) pages.4. This question paper contains SIX (6) questions.

Examination Data:Unit Weight of Wet Concrete 25 kN/m3

Available from Invigilator: Graph papers


Q.1

(a) A single skin wall form is erected for concreting a wall 1.5 m thick, 14 m long and 5 m tall next

to an existing structure as shown in Fig.Q1. Two rows of struts will be installed at the elevations

1 m and 3 m respectively above the ground level. Assume the following design information:

Wet Concrete Unit Weight 25 kN/ m3

Concrete Temperature Range 5 – 40C

Rate of Concrete Placement 3 trucks of 4.5 m3 per hour

CIRIA Report 108 Formula for Concrete Pressure

in kPa, or

(i) Determine the Concrete Pressure and plot its variation with the height of the formwork

(8%)

(Ans. 87.79 kPa, Trapezoidal Distribution – Triangular 0 - 87.79 kPa for 3.51 m

and remains constant for 1.49 m therafter)

(ii) Determine the respective maximum spacing (to the nearest 25 mm) of struts P1 and P2 if

the safe working of the struts is 100 kN each. Assume a safety factor of 1.2 against

overturning for the wall form.

(8%)

(Ans. 750 mm c/c for P1 and 475 mm c/c for P2)

(b) State the legal responsibilities of a scaffolding work contractor according to the Construction

Safety Regulations under the Law of HKSAR Government.

(9%)

Q.2

(a) Prepare a method statement with illustrated sketches to show how an unauthorized concrete canopy

structure projected from an existing building could be demolished over a footpath with a

proposed vertical shoring structure. Assume the pedestrian traffic under the canopy work is to

be maintained while heavy duty steel beams and lattice shoring towers will be used in the

shoring works.

(16%)

(b) Explain with reasons the proper formwork striking procedures for each of the following permanent

cast in-situ Reinforced Concrete members:

(i) Floor slab designed as simply supported

(ii) Beam designed as cantilever

(iii) Slab on Beam cast in one go


(9%)

Q.3

Determine the maximum spacing (to the nearest 25 mm) of horizontal walings, vertical soldiers and tie rods of a timber vertical form panel suitable for casting a concrete wall 600mm thick, 6.5 m high and 12 m long, given the following design criteria and formwork material properties. You may use the maximum design concrete pressure for the whole height of the formwork throughout. Assume the casting is done with a single lift. Calculate the tension in the tie rods which keeps the double skins in position against the outwards concrete fluid pressure.

Casting Conditions and Design Criteria:Mix: OPC with retarder added

Concrete Temperature: 10-35 C

Pour Rate: 3 trucks of 4.5 m3 each per hour

Allowable deflection: not to exceed 1/360 of span

Allowable Values

Formwork

Component

Moment of

Resistance

(M=f Z)

Bending Stiffness

(E I)

Shear Load

(q A)

Plywood

Sheeting

0.420 kNm/m 3.25 kNm2/m 6.86 kN/m

Waling 2.025 kNm 119.14 kNm2 9.80 kN

Soldier 10.5 kNm 200.35 kNm2 45.50 kN

(25%)

Hint: in kPa, or

Max. Bending Moment for a continuous beam under UDL

Max. Shear Force


Deflection = 0.007 for plywood

= 0.004 for waling and soldier,

where ω = Uniformly Distributed Load (UDL) on span L (kN per metre run)

(Ans. Pmax 83.09 kPa; Waling at 125 mm, Soldier at 1375 mm and Tie Rod at 650 mm c/c;

Tension 74.26 kN)

Q.4

(a) A double row access scaffolding of 4 bays and 4 lifts is assembled from mild steel

scaffolding tubes and fittings (BS 1139). The front and side elevations of the scaffold structure

are shown in Fig. Q4a. It is intended for the access and the working place of the operatives

working adjacent to the external wall of an existing building. Examine the scaffolding layout

carefully to identify if there are any safety deficiencies in the construction provisions according

to the general legal requirements of the Law of Hong Kong. State the deficiencies and prepare

an improved layout sketch for the scaffolding structure.

(10%)

(b) Fig.Q4b shows a timber wall form equipped with a working platform at the top and kept stable

with three (3) raking struts. Using the loading indicated below and the design information shown

in the diagram, calculate the maximum force in each raking strut if the whole temporary structure

is to be provided with a minimum safety factor of 1.2 against overturning:

Loading

Full Wind Moment (acting on wall form) 9 kN-m per m panel length

Working Wind Moment (acting on wall form) 5 kN-m per m panel length

Full Operation Load (acting on the working platform) 1.5 kN/m2

Nominal Access Loading (acting on the working platform) 0.75 kN/m2

Unit weight of Wall Form per face 60 kg/ m2

Hint:1. Consider the following three possible scenarios:

full wind + nominal access working wind + full operation 10% minimum lateral stability (Assume notional lateral force acting at ¾ of the formwork height) + full operation

2. You may ignore the stabilizing moment due to the self weight of the wall form.

(15%)

(Ans. 20.79 kN)


Q.5

Fig.Q5 shows the elevation layout of a typical transverse row of a working platform measured 5.2 m (H) and 8.4 m (W). There are 10 rows of scaffolding framework in longitudinal direction assembling from mild steel tubing and fittings all complying with BS1139. It is designed to support a uniformly distributed vertical load of 8.0 kPa (which has included the selfweight of the falsework structure, and operation loads). The design wind speed Vd in the vicinity of the structure is 39 m/s. Assume the scaffold structure is having a side board of 0.2 m high at both peripheral ends of the roof level. The longitudinal spacing of scaffold is at 1.5 m center to center while the solidity ratio of the scaffold area exposed to the transverse wind is 8%.

(i) Determine the total wind moment acting on the falsework structure. Assume that the dynamic wind pressure is given by and pressure coefficient Cf = 1.3 and 1.8 for circular scaffolding tubing and the side board respectively.

(5%)(Ans. 21.06 kN-m per row)

(j) Determine the total leg load in kN in each individual verticals (standards) of the scaffold structure under the combined vertical and wind loading condition. Using the Table 1 to check the axial loading capacity of the verticals against lateral buckling. Assume all scaffolding tubes are of “USED” condition. Identify if there are any verticals under tension.

(13%)(Ans. 5.74, 13.36, 13.77, 14.19, 14.61, 15.03, 15.44 and 8.66 kN;

No Buckling and None of verticals are under Tension)(k) Determine the minimum number of diagonal braces required to resist the

horizontal wind load. Draw the layout of the diagonal braces provided for the scaffold structure.

(4%)(Ans. Two Diagonals per row)

(l) If the self weight of platform structure is 1.0 kN per m2 plan area, determine the safety factor against overturning for the platform structure when it is subjected to the given wind loading.

(3%)


(Ans. 2.51)


Q.6

A single-propped cantilever steel sheet piling wall is designed to resist a 7.5 m high vertical cut. Given the following soil properties and design information:Height of soil to be retained 7.5 m

Depth of the prop below ground level 0.85 m

Horizontal spacing of props 3.2 m

Active Earth Pressure Coefficient 0.33

Passive Earth Pressure Coefficient 2.75

Unit weight of soil 18 kN/m3

Surcharge Load 15 kN/m2

Use FREE EARTH SUPPORT METHOD to:(iv) Draw the sketch to show the variation of the net soil pressure

with the depth of the sheet pile driven (3%)

(v) Determine the depth of point of zero net earth pressure (3%)

(Ans. 1.14 m)(vi) Calculate the strut load (12%)

(Ans. 390.4 kN).(vii) Determine the minimum depth of embedment that the pile has

to be driven. (7%)

(Ans. 4.21 m )


Thickness 1.5 m

Concrete Level

Wall Form

. .’ .P1 H = 5 m

2 m Strut

Existing Structure

1m P2

Fig. Q1

(Not To Scale)

External Wall

1.5m

wide

4 Lifts

each

1.8 m

high

Ground

Level

Fig. Q4a


(Not To Scale)


900

Wall Form

Length 10 m

Height 6 m Working Platform (Width 900mm)

Formwork 6 m

Members

19 mm Plywood 3 m

75x150 Waling Raking Strut (3 Nos)

100x225 soldier

60

Fig. Q4b

(Not To Scale)

Uniformly

Distributed Load

Toe Board 200 mm high 200

WIND

4 lifts each

1.3 m high

Ground Level

7 bays each 1.2 m wide

Fig. Q5


(Not to Scale)


TABLE 1 Maximum Permissible Compressive Loads in Steel Scaffolds

(which are manufactured in accordance with BS 1139: Section 1.1:1990 with a yield stress of 225 N/mm2)

Effective Length (mm)

Permissible Axial Compressive Load (kN)

As “New” Tubes As “Used” Tubes250 76.4 70.0500 74.5 63.3750 70.7 60.11000 64.3 54.71250 55.3 47.01500 45.3 38.51750 36.4 30.92000 29.3 24.92250 23.9 20.32500 19.8 16.82750 16.6 14.13000 14.1 11.93250 12.1 10.33500 10.5 8.93750 9.2 7.84000 8.1 6.94250 7.2 6.14500 6.4 5.54750 5.8 4.95000 5.2 4.45250 4.7 4.05500 4.3 3.75750 4.0 3.46000 3.6 3.18000 1.3 1.1


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