Comparison of Seismic Analysis Methods in Estimating of Steel Arch Bridge

The dynamic characteristics of different structures have led to the development of various analytical methods for analyzing the seismic behavior of structures. The existence of a predominant period in the structure is one of the features that can be used in analytical simplifications. Steel arch bridge is one of the systems for covering relatively long span. Mass distribution of steel arch bridge is the most important reason complexity of their seismic analysis. In this study a 300m span steel arch bridge has been investigated as a sample in the longitudinal direction. A comprehensive study has been carried out on the application of a capacity and demand prediction procedure based on incremental dynamic analysis with 17 seismic records for seismic performance evaluation of that bridge. Also results of IDA have been compared with nonlinear pushover analysis, and incremental dynamic analysis with sinusoidal record. Load pattern of pushover analysis is considered in two cases: inertia force distribution and modal force distribution. Nonlinear material effects are considered in the form of a concentrated plastic joint. The results show that Mass distributions of steel arch bridge due to this structure have not a predominant period and their seismic behavior is different under different accelerations because different mode shapes of structure are incitement. Also, by removing the mass of the arch element of the bridge and creating a model with predominant mode in the longitudinal direction, the results of its incremental dynamical analysis and nonlinear pushover analysis are investigated. Finally, a new approach is used for IDA by selecting harmonic base acceleration functions. This method is able to reduce the calculation cost of IDA with same accuracy of ground motion time histories.