Seismic Retrofit of an Existing Steel Arch Bridge Using Viscous Damper

Abstract

In Japan, the seismic behavior of the bridge structures is a much under-researched area of the civil engineering field since bridges have enormous importance and number for providing connection between the scattered islands. In this sense seismic design and analysis methods are paid much attention to get optimum behavior under severe earthquakes during bridge service life. In this paper, the retrofitting process of an existed upper-deck type steel arch bridge located in the Ground Type I which include good diluvial ground and rock is investigated. Since the bridge has been designed by the old code of 1980, it is in need of retrofitting. As a first step of dynamic response analysis, the dynamic characteristics along both longitudinal and transverse directions are analyzed by eigenvalue analysis to figure out the natural behavior under the dead load. The nonlinear dynamic response analysis is conducted under Hyogoken Nanbu earthquake occurred in 1995. After detecting the critical sections as abutments the viscous dampers are installed to increase the seismic performance of the bridge under severe earthquakes. The comparative results between undamped and damped structures are presented in terms of acceleration and displacement values at the critical points to evaluate the advantages of dampers. By this research, an application of seismic retrofitting and isolation methods are presented.