Question

2. The figure below shows a simply supported beam and its cross section at mid-span. The beam supports a uniform service (unfactored) dead load of 1.4 kips/ft plus its own

weight and a uniform service (unfactored) load of 1.5 kips/ft. The concrete strength is 3500 psi and the yield strength of the reinforcement is 60,000 psi. Use load and strength reduction factors from ACI 318-14 Chapters 5 and 21. a) Compute the factored ultimate moment Mu b) Based on section equilibrium, determine the compressive force in concrete and tensile force in steel. Use the simplified Whitney's stress block for concrete compressive force c) Determine the depth of neutral axis for this section d) show that the tension steel is yielding e) Compute ¢Mn and show that it is greater than Mu-

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