11.3. Material strengths are fy = 60 ksi and f = 4 ksi. A 12-span continuous reinforced concrete T beam is to carry a calculated dead load of 900 lb/ft including self-weight, plus a service live load of 1400 lb/ft on uniform spans measuring 26.5 ft between centers of supporting columns (25 ft clear spans). The slab thickness is 6 in., and the effective flange width is 75 in. Web proportions are b₁ = 0.6d, and the maximum reinforcement ratio will be set at 0.011. All columns will be 18 in. square. Material strengths are f 4000 psi and f, = 60,000 psi. =
(a) Find the factored moments for the exterior and first interior span based on the ACI Code moment coefficients of Table 11.1.
(b) Find the factored moments in the exterior and first interior span by elastic frame analysis, assuming the floor-to-floor height to be 10 ft. Note that alternative live loadings should be considered (see Section 11.2a) and that moments can be reduced to account for the support width (see Section 11.5a). Compare your results with those obtained using the ACI moment coefficients.
(c) Adjust the factored negative and positive moments, taking advantage of the redistribution provisions of the ACI Code. Assume that a 10 percent minimum redistribution is possible.
(d) Design the exterior and first interior spans for flexure and shear, finding concrete dimensions and bar requirements, basing your design on the assumptions and modified moments in part (c).