Forced Based Design Methods Vs Direct Displacement Based Design Method: A Novel Approach to Seismic Design of High Rise RC MRF Buildings with Light Weight Non-Structural Elements in High Seismic Regions of Pakistan

Abstract

With the evolution of seismic hazard knowledge and awareness, numerous seismic design approaches have emerged in the last three decades as a response to mitigate discrepancies in seismic forces and reduce vulnerability of our structures. The most simplistic and widely used approach are linear seismic design methods given in different national building codes including Equivalent lateral Force Procedure (ELF), Response Spectrum Analysis (RSA), and Linear Time History Analysis (LTHA). These established methods are extensively used for low to medium rise buildings with lesser seismic hazard. However, research in the past three decades showed that there are many fundamental problems associated with many assumptions of Forced Based Design (FBD) such as use of constant response modification factor (R), use of fundamental period, elastic damping ratio of 5% in design which leads to unrealistic capacity and demands in design. Past earthquakes like Northridge (1994) and Kobe (1995) etc., exposed vulnerability of structures and highlighted discrepancies of FBD approach. To overcome shortcomings in FBD, many alternative designs approaches based on performance-based design were proposed. Direct Displacement based design (DDBD) which is an offshoot of performance-based design became very popular in the past two decades due to its rationality and simplicity. DDBD uses the calculated secant stiffness instead of initial stiffness, equivalent viscous damping, and damping parameters etc. Recently, numerous advancements in durable lightweight construction materials have taken place which has impact on oscillation of structure due to reduction of mass when incorporated as a construction material. However, the impact of the use of such lightweight concrete on overall structural performance considering DDBD approach needs more extensive research. In this study, a prototype 12-story building is designed through Forced Based design methods such as ELF, RSA, LTHA followed by Direct displacement-based design approach. To investigate the multiperformance designing capability, the building frame is also designed for various performance levels given in FEMA 356 such as immediate occupancy, life safety,