DYNAMIC RESPONSE OF CABLE STAYED BRIDGES WITH DIFFERENT DAMPERS

Abstract

Cable stayed bridges, owing to their long-span and flexible structure, are subjected to vibrations due to environmental and service loadings. To alleviate these vibrations several methods have been reviewed in the past, out of which the use of dampers is rendered most suitable. Design of dampers however, is very important and previous studies have not detailed any design criteria for it. In this study, effort has been made to understand the effects of various damper properties on the damper design as well as the structure in general, when subjected to ground motions. A reference model of 40 m span twin tower cable stayed bridge is designed in SAP2000 Ver. 14 Program. Damper elements are modelled using link elements. Two types of dampers have been opted for the study i.e. linear viscous damper and friction damper. Since various earthquake records, even of the same strength, give extensively fluctuating structural responses, results gained using a single record may not be decisive. Therefore. three time-history records have been considered in this work including user-defined sine function, El Centro and Taft ground accelerations. The parametric study of dampers gives the effects of damper mass and damping coefficient on the overall damper performance and hence, a suitable range of these properties is identified. Further, the behaviour of different dampers under all the load cases is studied and a comparative study on the respective bridge response is carried out. It has been found that friction damper with a slip load of about 0.5 times the maximum damper force gives the optimum results.