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UNIWRSITY OF LONDON

MSc Examination 2007

MSc in General Structural EngineeringMSc in Structural Steel Design

For Internal Students of the Imperial College of Science, Technology and Medicine

Thispaper forms part of the examination or the Diploma of Imperial College

Plated Structures

Thursday 26 April 2007, 10.00-12.00

AnswerTWO questions. All questionscany equal marks.

Candidatesare required to bring BS5400-3:2000to the examination.

2007 University of London

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Question 1.

Briefly describe two key effects that contribute to the load carrying response ofplates being different from that of conventional (one-dimensional) structuralcomponents.

(4 marks)(b) (i) Explain, with the aid of simple sketches, the rationale behind the Von Karrnaneffective width concept. (2 marks)

(ii) Show that the Von Karman effective width concept gives the ultimate strength of acompressed rectangular plate as om, = (G,, ~ J ' ~ .(3 marks)

(iii) Discuss how BS 5400: Part 3 incorporates a similar approach to the Von Karmanapproach for the design of compressed plates. Explain why you would expectthese two methods to yield different results. (2 marks)Describe how longitudinal web stiffeners can be effectively used to increase thebending and shear strength of plate girders (4 marks)Illustrate how the elastic buckling stress of plates in compression and plates inshear are influenced by the aspect ratio of the plate. (5 marks)

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Question 2.Sketch and briefly describe the four principal buckling modes stiffenedcompression flanges are susceptible to. Discuss how B S 5400: Part 3 accounts forthese buckling modes in design.

(6 marks)(b) (i) The two box girders shown in Figure 4 2 are subjected to sagging bending moment.Calculate the load carrying capacity of the compression flange of each box usingBS 5400: Part 3. All steel has a y ie ld strength of 245 ~ / m m ~ .ssume C to beequal to 0.5 in the calculation of A. Make a suitable assumption for the position ofthe neutral axis in the stiffened box girder. (12 marks)

(ii) Com ment on the relative merits of the two designs. (2 marks)

Figure 4 2

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' "A "effects in: (i) beams(iij plates in compression(iii) plates in shear

(6 marks)

Describe how you would determine an initial sizing for a plate girder. (4 marks)A plate girder is fabricated from a 900 mm x 6 mm web and tw o 60 0 mm x 25 mmflanges. The yield strength of the steel is 240 ~ l m m ~ .he web is stiffened byrigid transverse stiffeners at 1260 mm centres, and adequate bracing is provided toprevent lateral torsional buckling from occurring. The section is non-compact, bu th l l y effective. Check the adequacy of this section to carry a shear force of 300 kNand a co-existent bending moment of 2900 kNm. Comment on your findings.

(10 marks)