PERFORMANCE BASED DESIGN OF RC FRAME BUILDINGS WITH SUPPLEMENTAL DAMPING",

Abstract

Traditionally all structures are designed using force based methodologies. But of late, Performance Based Design (PBD) has emerged as the most rational and viable approach for the design of ordinary as well as important civil structures in order to cater to the varying demands of clients. The current design guidelines in many countries encourage PBD approach both for the design of new structures and retrofitting of existing structures. In PBD, the performance of structural components is controlled by the limiting the inelastic deformation or member plastic rotations, while non-structural components performance is controlled by limiting the inter-storey drift ratios for a specified hazard level. A relatively new technique for earthquake resistant design of buildings consists of energy dissipation devices in combination with conventional lateral load resisting systems. Energy dissipation device is used to reduce the structural response by increasing the dissipation of energy imparted during an earthquake. Many methods are available in literature for the estimation of seismic performance of buildings with and without dampers, and for design of dampers and their optimal placement along the height of buildings. However, the methods for designing the combined building-damper system to achieve the target performance objective(s) with optimal placement of dampers are lacking. Hence, a step-by-step methodology has been proposed to design of buildings with energy dissipation devices to achieve the target performance objective(s). The methodology provides the amount of lateral force to be used for design of building structure, amount of damping required and placement of damping along the height of the building. Two case studies are presented to demonstrate the proposed methodology. In the first case study, energy dissipation devices (viscous fluid dampers) are provided to cater for the entire seismic demand imposed on a building designed for non-seismic forces. In situations where the dampers alone are not sufficient to resist the entire seismic demand, the proposed methodology stipulates for the enhancement in the capacity of original building. This two way approach to meet the desired performance objective(s) of a building has been illustrated by the second case study.