Uncoupled Compression Membrane Analysis of Reinforced-Concrete Members Subject to Extreme Loads

Abstract

An analytical procedure was developed to predict the compression membrane behavior of laterally restrained reinforced concrete members subject to extreme loads, such as those generated by the loss of bearing elements or during the application of excessive lateral loadings (e.g., explosions and impact). The procedure is based on the simplifying assumption that flexure and arching calculations can be uncoupled and that beam growth due to flexure after cracking can be approximated using rigid body rotation of beam half-segments. A lumped inelasticity flexure analysis is first performed to determine the degree of contact between the beam end and lateral support. The arching contribution to load capacity is computed by considering equilibrium of the contact zone arising from the projection of the beam into a partially rigid support. The total compression membrane strength is taken as the superposition of flexure and arching strength components. The methodology can handle supports with both rigid and nonrigid lateral restraint and varying degrees of rotational fixity. The numerical procedure has been verified extensively against the results of laterally restrained beam-column assembly and slab tests reported in the literature. The methodology can be used to model arching action under quasi-static conditions, or for inelastic dynamic analysis of structures subjected to blast and impact, provided high strain rate material properties are incorporated.