SEISMIC RESPONSE OF RC BRIDGES WITH VISCOUS DAMPERS

Abstract

Most structures are subjected to vibrations. These vibrations may arise from wind forces, earthquake excitation, machine vibrations, or many other sources. However, for structures subjected to strong vibrations, the inherent damping in the structure is not sufficient to mitigate the structural response. In many situations, supplemental damping may be used to control the response of these structures. In this regard, many researchers have studied, developed and tested different supplemental damping techniques. For any system, if the resisting force is proportional to the velocity of the motion, the system can be considered viscously damped. Fluid viscous dampers operate on the principle of fluid flow through orifices. A stainless steel piston travels through chambers that are filled with silicone oil. Fluid viscous dampers have the unique ability to simultaneously reduce both stress and deflection within a structure subjected to a transient. This study deals with the modeling of viscous dampers, proportioning of viscous dampers to achieve a required system damping ratio and analysis and behavior of a typical multi span simply supported viaduct with and without dampers. The nonlinear modeling of the bridge is carried out as per the guidelines of AASHTO(2005) and SDC(2004). Non linear direct integration time history analysis of a two span simply supported viaduct is carried out to study the advantages of adding supplemental viscous dampers. A comparison is done between the response of bridge with and without viscous dampers. It has been found in the study that for a bridge with supplemental dampers, the pier top displacements reduced by about 50%, the maximum bending moments in the piers were less by 30% and the inelastic rotations in the pier were less by 45% compared to the bridge without dampers.