TM 5-809-3/NAVFAC DM-2.9/AFM 88-3, Chap. 3
V2 = 5604 lb > Vallow = 3142 lb; Therefore, web reinforcement is required at both ends of the span.
(c) The area of the shear reinforcement required, Av, is determined as follows:
Where:
Fs = The allowable stress in the steel, psi
= 24,000 psi
s = The spacing of the shear reinforcement, in inches. The spacing of shear reinforcement should
not exceed d/2 nor 24 inches. The maximum spacing,smax, of the shear reinforcement is:
smax = d/2 = 20.62 in/2 = 10.31 in
Use s = 8 in (modular in reinforcement CMU)
Use 1-#3 bar (Av,= 0.11 in2), with web reinforcement provided starting at 4 inches from the face of the
support, spaced at 8 inches on center, to the first 8-inch module beyond the inflection point plus one-sixteenth
of the span as shown on figure 8-10.
(d) When all of the shear is resisted by the reinforcement the maximum allowable shearing stress,
Max Fv = 3%f*m not to exceed 120 psi
Max Fv, must be checked as follows:
= 3%1350 lb/in2 = 110 lb/in2 < 120 lb/in2
Use Max Fv = 110 lb/in2
fv = 41.02 lb/in2 < Max Fv = 110 lb/in2
...Shear O.K.
8-15
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