A simply supported beam (Figure) with a span of L=20ft is subjected to a uniform service load of 1200 lb/ft, including self weight, and a live load of 900 lb/ft. Determine the maximum factored vertical shear, Vu at the critical section, and the contribution of concrete to shear resistance, Vc.
The maximum shear Vmax is:
The maximum factored shear Vu, at a distance d away from the supports, is:
The moment at Vu (MVu), by equilibrium of the cross section, is:
The formula for Vc is:
Therefore, we get: