A1 A Reinforced Concrete Beam Is Simply Supported Over An 8m Span With A 4m Cantilever Span Projecting Beyond The Left 1 (75.37 KiB) Viewed 59 times
A1 A Reinforced Concrete Beam Is Simply Supported Over An 8m Span With A 4m Cantilever Span Projecting Beyond The Left 2 (40.59 KiB) Viewed 59 times
A1 A reinforced concrete beam is simply supported over an 8m span, with a 4m cantilever span projecting beyond the left hand side support, as shown in Figure A1(a). The beam supports a characteristic uniformly distributed permanent load of 10kN/m and concentrated characteristic variable imposed loads P1 = 80kN and P2 = 110kN. Ignore self-weight of the beam. Partial safety factors for loads: Permanent: maximum 1.35; minimum 1.0. Imposed: maximum 1.5; minimum 0.0. (a) By considering a suitable load pattern or patterns and using appropriate partial safety factors for loads, determine the maximum design sagging bending moment for the 8m span. Draw the design bending moment envelope for the entire beam. [10 marks] (b) The beam in Part (a) is a rectangular section 350mm wide, reinforced in the 8m span with 3H20 bars at an effective depth from the top of the beam d = 450mm is proposed (see Figure A1(b)). Check if the bending resistance of the proposed design is adequate For concrete section analysis, a simplified rectangular stress block, of depth 0.8x and subject to uniform design stress 0.85fcx/1.5, may be used. The requirement in A1(b) should be satisfied. Any assumptions made in analysis should be clearly stated Materials data: Characteristic yield stress of steel 500N/mm2, partial safety factor for steel 1.15. Characteristic cylinder strength of concrete fck = 35N/mm², partial safety factor for concrete 1.5. [10 marks] (c) Classify this section as an under-reinforced, over-reinforced or balanced section. Explain the reasons. [5 marks]
P = 80 kN 10kN/m P2 = 110 KN minimum k 4 m **2m 2m * 6 m nk C A B D (a) 350 mm 450 mmm K 3H20 (b) Figure A1
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