PERFORMANCE OF FRAME BUILDINGS WITH PASSIVE ENERGY DISSIPATION DEVICES

Abstract

A relatively new technique of earthquake resistant design of buildings consists of energy dissipation devices. In the present study, performance of a 10-storey RC Frame building designed for gravity load was improved by the use of hysteretic and friction dampers in order to achieve the target performance objective of Immediate Occupancy (I0) level. A Performance Based Design methodology for the dampers is proposed in the dissertation. The previous studies always aim in achieving target roof displacement or target inter-storey drift without taking into consideration of achieving target performance level in terms of plastic hinge rotation also. In this study target performance level is aimed to achieve both in terms of inter-storey drift and plastic hinge rotation. The basic idea of passive control system is to dissipate the energy imparted to the structure during an earthquake by converting the kinetic energy to heat or other forms of energy and thus limits the seismic damage of the building to these devices only which are easily replaceable. A non-iterative step by step design methodology has been proposed in this study to achieve the target performance level. The methodology provides the design parameters of the dampers — yield force (metallic dampers) and slip force (friction dampers). Here lead extrusion damper has been used as a type of metallic dampers which are connected to the frame by means of diagonal bracings. In case of friction dampers a simple slotted friction damper is inserted at the intersection of the cross bracings — the bracings being design for both tension and compression. A satisfactory distribution of both types of dampers along the height of the building has also been provided in the methodology. Validation is done to check the adequacy of the proposed design methodology by non linear time history analysis. The building (modeled in SAP2000), with and without dampers, was subjected to five spectrum compatible time history with PGA of 0.24g and the relative performance of the building with the two types of dampers is studied.