Assessment of inelastic performance of flat plate and wide beam frames

Abstract

Structural systems such as – flat plates and wide beam column frames are often preferred over conventional beam column framing systems because of architectural, functional and economic considerations. While comprehensive design guidelines are available for beam column systems, more rigorous analytical and experimental observations are required to develop comprehensive design guidelines for flat plates and wide beam column frames. As such the aim of this research is to study the nonlinear behavior of flat plates and wide beam column frames and compare their seismic performance as compared to that of beam column frames.

A 10-storied readymade garments factory building have been used in this study. Firstly linear static analysis have been performed following BNBC 1993 and three type of structures, i.e. beam column frames, flat plates and wide beam column frames have been designed. Nonlinear static analysis for maximum considered earthquake (MCE), design basis earthquake (DBE) and serviceability earthquake (SE), has been conducted for these three type of structures by using linear analysis data to understand the nonlinear behaviour for moderate seismic zone (zone 2) as per BNBC 1993. As nonlinear performances- maximum displacement, base shear capacity and hinge formation were determined according to ASCE 41 ‘Displacement Coefficient Method’. In nonlinear static analysis, parameters like story height, material strength have been varied for all types of structural systems for comparison of results.

While beam column frame systems perform much better than the other two systems in linear static analysis, flat plates have been found to possess much higher base shear capacity when nonlinear static analysis is employed. Wide beam column frames, though less costlier than flat plates, are structurally much less inferior compared to any other systems. As such flat plates structures should be preferred over wide beam column framing systems from architectural or functional point of view. The discrepancy in the results obtained from linear static and nonlinear static analysis calls for measuring nonlinear performance of sensitive structures.