System identification, model updating and seismic performance assessment of stone arch bridges

Abstract

Modernization of Samsun- Kalin railway line which is 378 km long has been un dertaken by Turkish State Railways. Due to their historical significance, 41 stone arch bridges on the line were decided to be preserved. Samsun-Kalin line passes through North Anatolian Fault, resulting in high seismic demand on bridges. In this study, seismic assessment of the bridges was carried out by Finite Element Analysis; however, masonry structures such as stone arch bridges have higher significant uncertainties compared to concrete or steel structures in terms of material properties, boundary conditions and modeling assumptions. Therefore, it becomes almost unavoidable to perform dynamic identification tests to validate Finite Element Models (FEM). In this study, dynamic properties of the bridges were identified by Enhanced Frequency Do main Decomposition method. Vibration measurements were collected under ambient conditions, impact loading and train passage. Based on identified modal parameters, FEM of the bridges were updated to obtain actual values of Young’s modulus and soil spring values. FEM updating procedure was performed by minimizing the difference between experimental and analytical modal values. Seismic performance assessment of the bridges was performed by pushover analysis and nonlinear time history analy sis. Nonlinear models were created by ANSYS software. As a next step, the results of pushover analysis were compared with 11 nonlinear dynamic analyses in terms of stress distribution of structural components and maximum displacement of determined control node. It was found that capacity of the bridges was affected mostly by the arch length.