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07-Str-A5: May 2013

Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)

  1. Question 1 Stiffened welded plate girder — flexure, shear and interaction
  2. Question 2 Plastic design of the rigid frame and the footing at D
  3. Question 3 Welded corner connection at B, and the beam-column AB
  4. Question 4 Unshored composite floor beam for a heavily loaded warehouse
  5. Question 5 Reinforced concrete frame — limit states design of member BC
  6. Question 6 The beam-column CD, and the reinforcement at the rigid connection B
  7. Question 7 Post-tensioned prestressed concrete girder

Start with Question 1 →

Paper format. 07-Str-A5 Advanced Structural Design, National Examinations, May 2013 — three hours, "closed book" with handbooks and textbooks permitted and one approved Casio or Sharp calculator. Seven questions are printed; any five constitute a complete paper and all questions are of equal value (20 marks each, split 12 + 6 + 2 or 12 + 8 or 14 + 6 or 15 + 5 as printed on page 1). All seven questions are solved here, because this set is a study resource rather than an examination script.

Design data printed on page 1 (used throughout). Design in SI. Concrete $f'_c=30$ MPa; structural steel $F_y=350$ MPa; rebar $f_y=400$ MPa. Prestressed concrete: $f_{ci}=35$ MPa at transfer, $f'_c=50$ MPa, $n=6$, $f_{pu}=1750$ MPa, $f_{py}=1450$ MPa, $f_{p,initial}=1200$ MPa, losses in prestress $=240$ MPa. All loads shown on the figures are unfactored.

Reference texts. CSA S16 Design of Steel Structures and the CISC Handbook of Steel Construction — plate girders (Cl. 14), plastic design (Cl. 8.6), beam-columns (Cl. 13.8), composite beams (Cl. 17) and connections (Cl. 21); CSA A23.3 Design of Concrete Structures — flexure, shear, columns (Cl. 10), footings (Cl. 15), joints (Cl. 21.7) and prestressed concrete (Cl. 18); NBCC for the load combinations; C. G. Salmon, J. E. Johnson & F. A. Malhas, Steel Structures: Design and Behavior; J. G. MacGregor & J. K. Wight, Reinforced Concrete: Mechanics and Design; T. Y. Lin & N. H. Burns, Design of Prestressed Concrete Structures; L. S. Beedle, Plastic Design of Steel Frames.

Check: load factors. The paper states only that "all loads shown are unfactored" and gives no dead/live split for the concentrated loads. Every question below therefore treats the printed concentrated loads as specified live load and factors them by $\alpha_L=1.5$ (NBCC principal load case $1.25D+1.5L$); self-weight, where it is significant (the plate girder, the concrete beam, the composite slab, the prestressed girder), is estimated from the trial section and factored at $1.25$. A candidate who assumed a different split would obtain proportionally different member sizes; the method is what is being examined.

Check: section properties. Rolled-shape properties (area, $I$, $S$, $Z$, $r$) are quoted from the CISC Handbook of Steel Construction, which candidates are permitted to bring into this examination. They are stated explicitly wherever they are used, so every subsequent line can be checked against them.