Sectional Depth of Prestressed Concrete Beams with Excess Capacity

In this paper, the requirements for the sectional depth of prestressed concrete beams satisfying the permissible stress limits are examined. An explicit expression for the member depth is derived in terms of three geometric parameters characterizing the cross section. It can be shown that the governing equation for the depth of prestressed concrete beams is a cubic equation consisting of only one real root. For design, an approximate solution is proposed for the beam depth, and the approximate solution is shown to provide good accuracy within the practical range of loadings and span lengths. The solution for sectional depth, however, does not guarantee a feasible section for the member, and a check on adequate cover for the prestressing tendon must be made during design.