(Standard hooks are depicted in Figure 1.) Reinforcement to be anchored to develop fy at the face of the support.These recommended details include the requirements for structural integrity reinforcement in ACI 318-14, Section 9.7.7, and can be used for beams that have been designed using the approximate bending moment coefficients in ACI Table 6.5.2. For beams subjected to uniformly distributed gravity loads where the shape of the moment diagram is known, the development lengths in Figure 1 can be used. Recommended bar extensions for flexural reinforcement in beams subjected to uniformly distributed gravity loads.ĪCI 318-14, Section 9.7.3, contains the requirements for the development of reinforcing bars in beams. Table 1 contains values of the minimum number of bars required in a single layer for various beam widths based on Grade 60 reinforcement ( f s = 40,000 psi), c c = 2 inches (1.5-inch cover plus the diameter of a #4 stirrup), and the overall longitudinal reinforcing bar diameter (approximate diameter to the outside deformations of the bar), which is given in Table 2.įigure 1. It is permitted to assume that f s = 2 f y/3 where f y is the specified yield strength of the reinforcement. Where f s is the calculated stress in the flexural reinforcement closest to the tension face of the section due to service loads and cc is the least distance from the surface of the reinforcement to the tension face of the member. Thus, the maximum center-to-center spacing, s, of the deformed longitudinal bars to limit crack widths is given by the following equation (see ACI Table 24.3.2): Reinforcing bars that are spaced too far apart could result in relatively large flexural crack widths. Minimum number of reinforcing bars required in a single layer.
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