Comparative Study for the Effect of Rigid and Semirigid Diaphragms on Reinforced Concrete Walls

Abstract

Rigid diaphragm is generally an acceptable option in most of the seismic design codes in which the in-plane deformability is not permitted because of the infinite in-plane stiffness properties.  Several building configurations may exhibit significant flexibility in floor diaphragms and accordingly using the semirigid diaphragm is recommended as significant in-plane deformation does occur.  In this study, a comparative study by using rigid and semirigid diaphragms is performed to identify the related effect on the reinforced concrete (RC) walls. In this study, a numerical study for a twelve-story building with dual system of RC columns and walls is performed. All geometrical and loading properties have been kept constant while using two types of diaphragm as rigid (RD) and semirigid (SRD). The seismic performance of the studied two structures was evaluated in terms of the fundamental period, maximum inter-story drift, maximum base shear and stresses on RC walls. Generally, RD produce results nearly identical to those of SRD for base shear, story displacements and inter-story drifts as the slab is sufficiently thick and membrane deformation due to lateral loading is negligible. Compared to SRD, using RD led to increase the internal moment and shear forces resulted from the seismic loads and acting on the RC walls while the resulting vertical loads are nearly identical.