THE UNIVERSITY OF NEW SOUTH WALES

SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING

FINAL EXAMINAnON - NOVEMBER 2008

CVEN 3302STRUCTURAL ENGINEERING 2

Time allowed - 3 hours

Total number of questions - 6

Questions are NOT of equal value

Answer Parts A on the Generalised Answer Sheet provided

Answer Part B in the Exam Book provided

Candidates may bring any aids to the examinationincluding electronic calculators

This paper may be retained by the candidate

All answers must be legibly written in ink. Pencils may onlybe used for drawings, sketches and graphs

In Part B, show all relevant working and state any assumptions made

PART A (70%) - Answer on the Generalised Answer Sheet provided

All Questions in Part A are of equal value

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~I ~RIO@250

3N28 ·I::!=~~---i

I .. 400 JSection A-A

f~ =32MPa

fsy =500MPa

Ec = 28 600 MPa

kcs = 1.86

r = 0.82

fsy.j = 250 MPa

Es = 200 000 MPa

Figure 1 (for questions 1, 2 and 3)

QUESTION 1

For the beam shown in Figure 1, based on the bending capacity of the section the designerdetermined the factored design load w* to be governed by (± 2 kN/m)

(a) w*:::; 155 kN/m(b) w*:::; 90 kN/m(c) w*:::; 72 kN/m(d) w*:::; 58 kN/m(e) w* > 90 kN/m

QUESTION 2

For the beam shown in Figure 1, the designer calculated Bv = 34 degrees and then determined

the section capacity Vu to be (± 10 kN)

(a) 417 kN(b) 292 kN(c) 204 kN(d) 143 kN(e) none of the above

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QUESTION 3

If the effective second moment of area for the beam shown in Figure 1 is 35% of its grosssecond moment of area (excluding reinforcing steel), the long term deflection of the beamunder a service load of w = 30 kN/m is

(a) 9 mm or less(b) between 10 mm and 19 mm(c) between 20 mm and 29 mm(d) 30 mm and 39 mm(e) greater than 40 mm

QUESTION 4

A simply supported timber beam spanning 3.8 metres and carrying a factored design load ofw* = 10 kN/m is continuously laterally supported along its critical edge. If the designer hasselected a beam of grade F15 timber and with a width of b = 72 mm, what depth of memberdid he select for an efficient design for flexure (do not consider shear or deflections)?

(a) 247 mm(b) 197 mm(c) 147 mm(d) 97 mm(e) a section with a depth, D, greater than 247 mm

For F17 stress grade, the bending stress limit is fb =50 MPa . Take rjJ =0.65, k1 =0.8 and

all other factors as unity.

QUESTION 5

850oil

ooLt)

f y =300MPa

16

16 16

Figure 2 (for question 5)

For the heavily welded steel section shown in Figure 2, and withJ;, = 300 MPa, the ultimate

axial capacity, Nu, of section is (± 20 kN)

(a) 8730 kN(b) 8010 kN(c) 7250 kN(d) 6530 kN(e) none of the above

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PART B (30%) - Answer in Exam Book Provided

QUESTION 6 (30 Marks)

Select a suitable 300 MPa grade universal beam (UB) section for the 3-span member B3shown in Figure 6. The beam is loaded, in addition to its self-weight, as follows:

120 mm thick concrete floor slabsuperimposed dead load = 1.0 kPalive load = 3 kPa

You are to check your section for bending, shear and deflections, fully justifying youranswers (checking only by use of safe load tables or charts isnot sufficient). Note that thereis no connection between the beams and the concrete floor slab and that the slab transfersload to the beams only in the direction indicated.

The bending moments and shear forces for the member for a uniformly distributed loadingare provided in Figure 4. The maximum deflection occurs in the outside spans and is given by

4L1 = 2.5 wL

384 El

For your deflection calculations, take the short term load factor as If/s = 0.7 and the limit onthe total deflections as span/250.

BI I~500(tyl

ooo"'"

B2

B3

ooo"'"

B4

B5

I

Ilater41 bracing

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ooo

"'"

ooo

"'"

PLAN

Figure 3 (for question 6)

4

M,

M,

V, =

V, =

Loading' ... '\','... ,'llllll

Reactions:

R, = R, = 4wLID

R = R. = IlwL'10-Shear forces:

V, = - V _ 4wLI - ID

6wL10

SwL10

Bending moments:Mm" = wL'-fer' at R.

and R.4wL' .s6 . at OAL- from R.

andR, '

wU46 ' at centl'l

Figure 4 (~or question 6)

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