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Unformatted text preview: Name ______________________________ Student Number ______________________________ DEPT. OF BUILDING, CIVIL & ENVIRONMENTAL ENG. - CONCORDIA UNIVERSITY BCEE 345 – STRUCTURAL DESIGN II (REINFORCED CONCRETE DESIGN) Winter 2007 Dr. K. Galal DURATION OF EXAMINATION: 11:45 to 1:00 pm THIS EXAMINATION PAPER INCLUDES 3 QUESTIONS IN 7 PAGES. YOU ARE RESPONSIBLE FOR ENSURING THAT YOUR COPY OF THE PAPER IS COMPLETE. BRING ANY DISCREPANCY TO THE ATTENTION OF YOUR INVIGILATOR. Special Instructions: 1- This is a CLOSED BOOK exam with the exception that students will be allowed to use an unmarked copy of the design standard CSA A23.3 i.e. PART I of the “Concrete Design Handbook”. The rest of the handbook should not be used. 2- This exam is for a total of 100 points. 3- Attempt ALL THREE questions. 4- The use of any programmable calculator is not allowed. 5- Use information provided. 6- If given data is not sufficient, assume reasonable values for any additional needed information. 7- State clearly all assumptions made. 8- This examination paper must be returned. Design aids: ⎛ 2 K r ⎞ α 1φ c f c′ ⎟ ▪ ρ = ⎜1 − 1 − ⎜ α 1φc f c′ ⎟ φ s f y ⎝ ⎠ φ s ρf y ⎞ ⎛ ▪ K r = φ s ρf y ⎜1 − ⎜ 2φ α f ′ ⎟ ⎟ c 1 c⎠ ⎝ ▪ ▪ ≤ ρ max = α 1 β1φ c f c′ ⎛ 700 ⎜ φ s f y ⎜ 700 + f y ⎝ ⎞ ⎟ ⎟ ⎠ Mr = bd 2 × 10 −6 Kr s ≥ 1.4 db , ≥ 1.4 amax , ≥ 30 mm ▪ min. clear cover to the outside of stirrups: 40mm (Exposed), and 30mm (non-exposed) ∆T ′ ▪ As = φ s f y − φ cα 1 f c′ ▪ ∆T =
M f − M r ( balanced ) d − d′ ▪ k = 2 ρ n + ( ρ n) 2 − ρ n ▪ Note: Areas and diameters of reinforcing rebars are in page 220 of the Concrete Design handbook Continued on page 2 2 Problem 1: [75 points] The following figure shows the elevation view of a factory. The factory has a 12.00 m simplysupported reinforced concrete girder that is supporting a moving crane. The maximum specified load that the crane can carry is 220 kN (including the weight of the crane). The load of the crane can be assumed as a single concentrated load (i.e. ignore the spacing between the wheels of the crane). The girder has a 400x750 mm rectangular cross-section. The compressive strength of concrete is 25 MPa and the reinforcement has a yield strength of 400 MPa. The maximum aggregate size used is 25 mm and the girder is non-exposed. It is required to:  1- Calculate the maximum factored bending moment on the girder.  2- Calculate the maximum amount of tension reinforcement allowed (without the use of compression reinforcement) and the corresponding moment capacity. [Hint: d can be assumed to be 660 mm]. Assuming that the maximum factored moment acting on the girder is Mf = 1152 kN.m, it is required to:  3- Determine the amount of flexural reinforcement required for the girder. (exact depth should be used in calculations). [Hint: use 30M rebars for tension reinforcement: its diameter is 29.9 mm and its area is 700 mm2]  4- Check the minimum steel requirement, minimum bar spacing, and crack control requirement. Calculate the amount of skin reinforcement, if needed. Moving crane 220 kN
A RC crane girder
A 12.00 m 750 400 Section A-A Continued on page 3 3 Continued on page 4 4 Continued on page 5 5 Continued on page 6 6 Problem 2: [10 points] The following figure shows a cross section of a 300x600 mm RC beam with the shown reinforcement. The beam is subjected to a service moment of 180 kN.m. The compressive strength of concrete is 25 MPa and the reinforcement has a yield strength of 400 MPa. The beam has interior exposure, and 10M stirrups are used. It is required to calculate the stresses in the concrete and tension reinforcement. 600 mm 4-25M 300 Cross section Continued on page 7 7 Problem 3: Answer briefly the following questions: [15 points] A. What are the five main groups of limit states? B. What are the three types of RC sections (with respect to the amount of reinforcement) and their corresponding failure modes? What is the favorable type of failure? How to ensure that a welldesigned beam will experience this type of failure? C. For the case of RC section that has a specific amount of As, draw on the following diagram the expected change in the strain distribution when having As'. What would be the expected change (approximately) in the moment capacity of the beam when having As'? A's εcu As As εs
The End Best wishes
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- Winter '07