Investigation of seismic performance for arch bridges with overpass box deck with and without LRB seismic isolator

Most of the bridges in the world are generally designed and built according to the old criteria and regulations, These bridges should be subjected to seismic improvement studies and strengthen with appropriate method if needed. One of the practical methods for assessing the performance of a structure under different levels of seismic hazard is the fragility models, which are presented as fragility curves. The fragility curve expresses the conditional probability of reaching or exceeding a limit state as a function of ground motion parameters and the probabilistic method is also used to consider the different states and uncertainties that affect structures and earthquakes.Boxed cross-section arch bridges have good mechanism for bearing vertical loads due to stability and proper distribution of gravity loads. LRB seismic isolation systems are used to improve the seismic performance of the bridge. This study investigates the seismic behavior of the Nanin Bridge Arc Case in Switzerland, which has a cross-section overpass deck with a LRB Then, by evaluating the structural response states and the capacity of the members. Examination of the results of the seismic response of this structure as well as the probability functions of the frailty curve in different situations showed that the use of this system resulted in a significant reduction in the amount of earthquake damage at all levels of failure in foundation. With the use of Rubber lead seismic isolator, displacement of the structural base, the likelihood of base failure and base shear has been greatly reduced and due to the use of maximum member capacity and reduced member dimensions as well as a significant reduction in the amount of financial damage the system has also benefited.