Question

2. A rectangular concrete beam is cast with 1-inch maximum aggregate size and measures 15 inches wide and has an effective depth of 21 inches. If the compressive strength of

the concrete is 4 ksi and the yield strength of steel reinforcement is 60 ksi: a) Calculate the moment capacity of the beam assuming the reinforcement is 3 #8 bars in one layer b) Assume that Mu calculated from the applied loads and self-weight is 400 k ft. Select the steel network for equilibrium (including number of bars). c) Using your answer for part b, check for all spacing requirements assuming number 3 stirrups are inside and the total beam height is 25 inches. If the steel cage you designed does not fit, re-design the steel cage so all design and ACI requirements are met. d) Calculate the area of steel needed for all following assumed reinforcement ratios. Neglecting the spacing criteria, which of these will options will support Mu? i. Pmin ii. PTC iii.(0.75)Pbal iv. Pbal

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