exams - se1m80-0607

7/28/2019 exams - se1m80-0607

http://slidepdf.com/reader/full/exams-se1m80-0607 1/7

SE1M80/Spring 2007/07pp

UNIVERSITY OF SURREY ©

School of Engineering

Programmes in Civil Engineering

Level M Examination

Module SE1M80; 15 Credits

Concrete Building Design

Time allowed: 3 hours Spring 2007

Answer FOUR questions only.

Each question carries 25 marks; where appropriate the mark carried by an individual part of a question is indicated in brackets [ ].

Additional materials:

Design data booklet

Note any assumptions made

Candidates are reminded to avoid use of red ink.

[SEE NEXT PAGE]

7/28/2019 exams - se1m80-0607


SE1M80/Spring 2007/07pp 2

1. Figure 1 shows the elastic moment diagrams of a two span continuous beam obtained

from the analysis of three load cases. The rectangular shaped beam spans between

supports at 8.0m centres.

(a) Redistribute support moments by up to 30% and produce an appropriate

moment envelope for design. Assume the loads cannot be handed.

[15 marks](b) Explain why you would redistribute moments in beams and not columns and

what restrictions are required?

[4 marks]

(c) Design the main longitudinal reinforcement at locations A and B.

[6 marks]

Figure 1 – Elastic moments

All moment values are in kNm.

Concrete strength C45/55

Characteristic yield stress of steel reinforcement (f y) = 500 N/mm2

Cover to main longitudinal reinforcement = 35 mm

Diameter of main steel = 32 mm

Height of beam = 500 mmWidth of beam = 250 mm

BA

75

240

300

300

Elastic

180

300

0

200

160

200

200

200

100

130

200

7/28/2019 exams - se1m80-0607



2. Figure 2 shows a column subject to axial load and moments about the x-x axis. The

effective creep ratio φef = 1.0, additional moments due to curvature have been

evaluated as 50kNm and those due to imperfections should also be considered.

Assuming the mechanical reinforcement ratio is not known at the design stage.

Determine the following :

(a) The effective height of the column. [2 marks]

(b) The slenderness ratio λ of the column [3 marks]

(c) The slenderness limit λ lim of the column. [4 marks]

(d) The equivalent first order moments M0e [2 marks]

(e) The design moment at mid height of a column. [2 marks]

(f) The maximum design moment at the column end [2 marks]

(g) Area of main reinforcement As required and how you would position this in

the column [10 marks]

550mm

10m

120kNm

NEd

= 3200kN

660kNm

All beams have twice the stiffness of columns.The column forms part of a bracedframe.

d2

= 50mm

f yk

= 500MPa

θi= 1/100

Concrete type C40/50FIGURE 2

x

x

4 5 0 m m

7/28/2019 exams - se1m80-0607



3. You are checking the design of a continuous reinforced concrete beam (Figure 3).

The main bars have a diameter of 25mm and the shear links are 12mm in diameter. In

the design, the bending moments were re-distributed by 30% and the client requires a

2 hour fire resistance. The nominal cover used is 40mm and the anchorage length

specified for all main tensile bars is 700mm. Figure Q3 indicates the section to the

beam at mid-span and the supports. If a C35/45concrete is specified, the beam is builtin an environment which is of moderate humidity and subject to carbonation effects,

and the design is for 100 years, check : -

(a) The nominal cover specified.

[8]

(b) The anchorage length specified. Check anchorage lengths for the main

reinforcement over the supports and at mid span. Assume α3 = 0.85, no

external pressures exist on the beam and the cross sectional area of transverse

reinforcement is 0.4 x area of the main reinforcement at that location. Only

undertake the anchorage check for those bars which are in the corners of the

beam.

[12]

(c) Make recommendations based on your findings.

[5]

400mm

6 0 0 m m

Reinforcementat mid span

Reinforcementover supports

FIGURE 3

7/28/2019 exams - se1m80-0607



4. A simply supported beam has a section as shown in Figure 4. The span of the beam is

8.0m and the beam carries a factored udl of 45kN/m which includes self weight.

Three (3) No. T32 bars are needed to resist the flexural effects on the beam.

Determine :

(a) The maximum design shear force.

[4]

(b) The shear resistance of the concrete.

[5]

(c) The shear reinforcement assuming vertical links as indicated in figure 4.

[5]

(d) The strength of the concrete “shear strut”.

[5]

(e) The shear reinforcement ratio and that it is acceptable.

[3]

(f) The maximum longitudinal spacing of the vertical links.

[3]

Vertical links

d = 500mm

f ck = 30/37

bw

= 300mm

3 No T32

f yk

= 500MPa

FIGURE 4

7/28/2019 exams - se1m80-0607



5. (a) The European code uses the standard deviation (and margin) of sets of

specimens in association with partial factors in the design process. Explain the

implications of an unexpected increase to the standard deviation of concrete

used in a large building on the design and hence discuss the importance of

quality control in the production and installation of concrete.[8]

(b) A continuous one way spanning reinforced concrete slab is shown in Figure 5.

For a 1.0m width of slab, the permanent load including self weight is

12.5kN/m, and the variable load = 40.0kN/m. Determine the worst support

and mid-span moments and hence the area of reinforcement per meter width

required in the slab. C30/35N/mm2 concrete is specified and no redistribution

of moments has been undertaken.

[10]

(c) During construction of the slab specified in section b) two major errors occur

simultaneously. Firstly the slab is constructed with an effective depth of

115mm but in addition, the concrete, when tested has a characteristic strength

of only 20N/mm2. Check if the slab, as built, will be under or over reinforced.

Discuss the implications these errors have on the slab in terms of ultimate

capacity and day to day service. Recommend remedial action.

[7]

A

3 5 0 m m

FIGURE 5

EDCB

7.0m7.0m7.0m7.0m

A

A

7/28/2019 exams - se1m80-0607



6. (a) A 6.0m long cantilever has a width of 300mm and is subject to a permanent

load of 7.4kN/m (including self weight) and a variable load of 15.0kN/m.

Determine the effective depth ratio of the cantilever for a balanced design at

ultimate load. Check to see if this value satisfies the effective depth at

serviceability loads. C40/50 concrete is specified.

[8]

(b) In the design of a reinforced concrete reservoir, the crack widths need to be

limited to 0.2mm. If the stress in the reinforcement at serviceability loads is to

be limited to 50% of the design stress, determine the maximum size and

spacing of reinforcement which can be used in the reservoir. f yk = 500MPa.

[8]

(c). A rectangular section of strength class C40/50 has b= 350, d = 400mm and As

= 2900mm2. What is the moment of resistance of the section when the stress

in the steel is 350MPa?

[9]

Documents

exams - se1m80-0607