Design of Prestressed Concrete Beams with Openings

Web openings in beams occur quite often in practice to provide convenient passage of environmental services. As a result, story heights in buildings can be reduced resulting in major cost savings. In this paper the nonlinear analysis and design of simply supported posttensioned prestressed concrete beams with rectangular openings are presented. Several design parameters are varied such as: opening width and depth, horizontal and vertical locations of the opening, and type of cross section. The results from a nonlinear finite-element analysis are substantiated by test results from 13 unbonded posttensioned prestressed concrete beams, six of which are rectangular in section, five are T-section, and the remaining two are I-section. Good agreement is shown between the theoretical and the experimental results. The effect of the openings on the behavior of such beams at different stages of loading is presented. A simple design method for estimating the ultimate failure load for each type of failure mode is proposed. An illustrative design example is presented.