A comparison of beam method and truss method for design of reinforced concrete deep beams

Abstract

The design of a reinforced concrete deep beam is usually governed by the shear strength. The flexural strength of the beam and the strength of the bearing area under concentrated loads are also of concern. A deep beam can be designed using truss analogy method by which the load is transferred via a system of compression struts, tension ties and nodal zones. On the other hand, the simplified design of a deep beam for flexural strength can be similar to that for a typical beam with modification to the internal moment lever arm to account for nonlinear strain distribution. In the paper, a number of simply supported deep beams with the span-to-depth ratio varying from 1 to 3 are investigated. The amount of reinforcement determined using the truss method is compared with that computed using the beam approach with the moment lever arm being either modified or taken as for a normal beam. The effect of the span-to-depth ratio on the extent of agreement among various design methods is then discussed.