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07-Str-A4: May 2018

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

  1. Question 1 Minimum structural degrees of freedom for a slope-deflection analysis (8 marks)
  2. Question 2 Schematic shear force and bending moment diagrams (12 marks)
  3. Question 3 Castigliano's theorem of least work on a two-member frame (16 marks)
  4. Question 4 Influence lines for a wall-braced pin-jointed truss (16 marks)
  5. Question 5 Uniform temperature rise in a three-column frame (16 marks)
  6. Question 6 Slope-deflection with a uniformly distributed load and a support that moves outward (24 marks)
  7. Question 7 Fixed-end moments of a non-prismatic beam by the flexibility method (24 marks)
  8. Question 8 Anti-symmetric portal with loaded columns and free stubs (24 marks)
  9. Question 9 Deriving the stiffness matrix and load vector of a frame with parallel legs (24 marks)

Start with Question 1 →

Paper format. National Examination, May 2018, 07-Str-A4 Advanced Structural Analysis — 3 hours, CLOSED BOOK (an approved Casio or Sharp calculator is permitted). Nine questions: #1 and #2 are compulsory (8 and 12 marks), then TWO of #3, #4, #5 (16 marks each) and TWO of #6, #7, #8, #9 (24 marks each); six questions constitute a complete paper (100 marks). All nine are solved here, because the set is a study resource rather than a timed sitting.

Reference texts.

Sign convention used throughout. Member end moments $M_{ij}$ are counter-clockwise positive on the member end, which is the convention that matches the standard 6-degree-of-freedom element stiffness matrix and the counter-clockwise-positive joint rotations that Question 9 asks for. With that convention the fixed-end moment of a downward uniform load is $M^{F}_{ij}=+wL^{2}/12$ at the near end, the chord rotation is $\psi_{ij}=\left[(\mathbf{D}_{j}-\mathbf{D}_{i})\cdot\mathbf{e}_{2}\right]/L$ with $\mathbf{e}_{2}$ the member axis turned $+90^{\circ}$, and the ordinary sagging moments plotted on the diagrams are $M_{\text{sag}}(i)=-M_{ij}$ and $M_{\text{sag}}(j)=+M_{ji}$. Where a step of the working is quicker in the clockwise-positive (Hibbeler) form the sign is stated explicitly.