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07-Str-A2: December 2013

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

  1. Question 1 Moments of resistance of a built-up box-and-plate section
  2. Question 2 Bolted beam-to-column connection and the steel tie
  3. Question 3 Maximum factored load on a free-standing sign standard
  4. Question 4 Design of a reinforced concrete T-section
  5. Question 5 Moment and shear resistances of a concrete culvert section
  6. Question 6 Design of a square reinforced concrete column
  7. Question 7 The same column designed as a Douglas-fir glulam member

Start with Question 1 →

Paper format. National Examinations, December 2013 — 07-Str-A2, Elementary Structural Design. Three hours; a "CLOSED BOOK" examination in which handbooks and textbooks are permitted. Seven questions in three parts — Part A steel (CAN/CSA-S16), Part B reinforced concrete (CAN/CSA-A23.3), Part C timber (CAN/CSA-O86). A candidate answers two questions from Part A, two from Part B and the single question in Part C, five in all, and page 1 records that all questions are of equal value, so each carries 20 marks with the split A1 (6 + 7 + 7), A2 (5 + 10 + 5), A3 (4 + 4 + 12), B1 (6 + 8 + 6), B2 (10 + 10), B3 (4 + 4 + 12), C1 (10 + 10) printed in the marking scheme. All seven questions are solved below.

Reference texts. CSA S16, Design of Steel Structures, used with the CISC Handbook of Steel Construction (section tables, Class H HSS, bolt and weld tables); CSA A23.3, Design of Concrete Structures, used with the CAC Concrete Design Handbook; CSA O86, Engineering Design in Wood, used with the CWC Wood Design Manual; National Building Code of Canada (load combinations); MacGregor and Bartlett, Reinforced Concrete: Mechanics and Design (Canadian edition); Kulak and Grondin, Limit States Design in Structural Steel.

Check — load factors used throughout. Page 1 note 6 states that all loads shown are unfactored but the paper nowhere splits them into dead and live. Every applied load in Figures A2, B1 and B3 is therefore treated as a specified live load and factored by 1.5, and self-weight, where a question asks for it, by 1.25, following NBCC load combination case 2, 1.25D + 1.5L. Question B3 names its 80 kN horizontal load as wind, so that question is additionally checked under case 4, 1.25D + 1.4W + 0.5L. If a grader intends a different dead/live split every factored action scales linearly and no design step below changes.

Check — steel grade in Figure A1. The A1 stem attaches "G40.21 300W" to the plates and is silent on the grade of the hollow section. All three components are taken as 300W, Fy = 300 MPa; if the HSS is in fact 350W the plates still yield first and the plastic moments quoted rise by less than 8 per cent. Corner radii of the hollow section are ignored (square corners), which is the usual hand-calculation idealisation and overstates the HSS area by about 4 per cent relative to the tabulated value.