A SIMPLIFIED DISPLACEMENT-BASED PROCEDURE FOR DESIGN & PERFORMANCE EVALUATION OF LOW- RISE MASONRY INFILLED RC FRAME BUILDINGS IN PAKISTAN

Abstract

Reinforced concrete frame structures with masonry infill walls correspond to a typical building topology in Pakistan and around the world. Masonry infill walls are regularly used in construction as internal partitions and external walls. Practicing engineers often employ the code based static procedures for structural design, neglecting the impacts produced by infill walls, since infill walls are believed to be non-structural components. However, the presence of infill walls may contribute to early strength, initial stiffness and energy dissipation capacity of the frame, thus considerably modifying the global seismic performance of frame buildings. There’s no practical scheme available to incorporate the effects of these infill panels in conventional static design procedures. To overcome this issue, this study presents a simplified displacement- based design (SDBD) procedure based on the concept of equivalent linearization and using the framework of direct displacement-based design (DDBD) method. The fundamental philosophy of this approach is that buildings should be designed to attain a definite performance level, when subjected to a definite hazard level. This procedure is developed using three case study RC infilled frame buildings (3-, 4-, 5-story high) and the accuracy of this proposed procedure is evaluated for a 5-story high building under specified level of ground motions. In this evaluation, the inelastic seismic demands estimated by nonlinear time history analysis (NLTHA) procedure are employed as a benchmark. It is shown that the proposed SDBD procedure can accurately estimate the local & global responses for infill RC frame building under input ground motions.