Direct Assessment of Safe Strengths of RC Slabs under Membrane Action

The determination of the strength of reinforced concrete slabs with proper consideration of the benefits of compressive membrane action is too complex for regular use by the practicing engineer. Following previous work on plastic flow rules and the relationships between rigid-plastic and elastic-plastic idealizations of laterally restrained one-way spanning slab strips, it is shown that the load at the maximum membrane force is expressed in a very convenient form for use in design. The formulation is given in this paper for strips and square isotropic slabs and is shown to provide a useful approximation of the theoretical full load capacity underestimating it by a margin that is larger when the sensitivity to in-plane stiffness is greater. A comparison is made with laboratory tests and a worked example shows how the parameters are employed.