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A rectangular beam has a cross section of b = 18 in., h = 24 in., and d = 21.5 in. It is reinforced with two No. 6 Grade 60 bars. The concrete strength is 6,400 psi (normal weight). The beam has Grade 60 No. 3 stirrups. Determine the cracked moment of inertia, Icr. The neutral axis location of the cracked beam (measured from the top of the beam) is 3.3587 in.

Determine the bar-spacing factor, cb, for a simply supported rectangular beam with b = 24 in. and No. 3 stirrups. This beam has three No. 7 bars as longitudinal reinforcement. The clear cover is 1.9 in.

Cracks due to shear are unable to cross into the compression zone of the member.

Universally accepted crack widths are specified in ACI 318.

Under sustained loads, concrete undergoes creep strains and the curvature of a cross section _______. Because the lever arm is reduced, there is a small _______ in the steel force, but for normally reinforced sections, this will be minimal.

The fatigue strength of concrete is not sensitive to stress concentrations.

Compute the maximum bar spacing, s, to control for cracks in a one-way slab with 1.5 in. of clear cover and f​y​ = 52 ksi.

In order for a reinforced concrete beam to function properly (concrete resisting compression, steel resisting tension), a bond must not exist between the concrete and the reinforcement.

A rectangular beam with cross section b = 14 in., h = 24 in., and d = 21.5 in. supports a total factored uniform load of 2.90 kips/ft, including its own dead load. The beam is simply supported with a 22-ft span. It is reinforced with five No. 8 Grade 60 bars, three of which are cutoff between midspan and the support and two of which extend 10 in. past the centers of the supports. The concrete strength is 3,900 psi (normal weight). The beam has Grade 60 No. 3 stirrups satisfying ACI 318-14 Sections 9.7.6.2.2 and 9.6.3.3. The strength of the five bars is φMn = 336.8 kip-ft, and the strength of the remaining two bars is φMn = 145.6 kip-ft. If the distance from the support to the theoretical cutoff point is 6.463 ft, determine the distance from the support to the actual cutoff point (i.e. use ACI 318-14 Section 9.7.3.3).

Heat-of-hydration cracking can be prevented by proper mix design and by preventing rapid drying of the surface during the first hour or so after placing.