RC Rectangular Slabs with Edge Restraints

Reinforced concrete slabs with edges restrained against lateral displacement are capable of carrying ultimate loads which are considerably higher than the loads predicted by using conventional yield-line theory. An analytical relation for the load-deflection behavior is derived in the paper by using a plastic-flow theory. The compatibility condition introduced in the paper for the deformation of the centerline of the slab incorporates boundary displacements as well as the in-plane deformations of the slab. Combining the compatibility condition, the flow rule associated with the load-moment yield criterion, and the axial equilibrium condition, a nonlinear differential equation is obtained for the membrane force in the slab. The load on the slab is then calculated for a given deflection by balancing the external and internal energy dissipation. The predicted load-deflection curves are compared with those obtained from two test series and a good agreement is obtained up to the peak load. The load-deflection curve beyond the peak load is found to be predicted better by the incorporation of an analysis which approximates strain softening of the concrete.