Compressive Membrane Capacity Estimates in Laterally Edge Restrained Reinforced Concrete One-Way Slabs

Abstract

The load capacity of laterally restrained reinforced concrete one-way slabs is estimated in compressive membrane theory with use of a midspan deflection. However, the midspan deflection estimates exhibit large variability. The point of peak thrust leads to a more accurate index of the peak load capacity than midspan deflection. The calculation of the thrust within the compressive membrane theory is a maximum when the slab's axial shortening and the outward support movement are a maximum. The use of the peak thrust to select the peak capacity, when combined with a modification to Park and Gamble's (1980) compressive membrane theory, provides an improved overall correlation to the experimental data for a large range of span-to-thickness ratios (2.7 < Lih <28.3). In this study, peak midspan deflection estimates were developed to define the peak point of the load-deflection curve. The slab's axial concrete compressive strength and the peak concrete compressive strain are used within a curvature and geometrically based deflection equation, to predict the midspan deflection. The post-peak trough and ultimate points are related empirically to the tensile membrane curve, and the generated load-deflection curve compares well with the experimental data. A simple compressive membrane load capacity estimate for laterally restrained reinforced concrete one-way slabs is developed for field use. The estimate uses the axial force-moment interaction equations and a ratio for the peak thrust to the slab's axial capacity, and results in an accurate estimate of the peak compressive membrane capacity using yield line theory.