System Identification and Seismic Performance Assessment of a Stone Arch Bridge

ABSTRACT

This paper presents system identification and seismic performance assessment of a masonry arch bridge located on the railway route which is on the northeastern part of Turkey. Forty-one masonry arch bridges were registered as historical and needed to be preserved on the route. On the other hand, the railway line passes through North Anatolian Fault, resulting in high seismic demand on bridges. Therefore, seismic assessment of the bridges was carried out by finite element analysis; however, masonry structures such as stone arch bridges have significant uncertainties in terms of material properties, boundary conditions, and modeling assumptions. As a result, it becomes almost unavoidable to perform dynamic identification tests to validate finite element models (FEM). Modal properties of 12 bridges such as modal frequencies, mode shapes, and modal damping ratios were identified through vibration measurements 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 of masonry and soil. FEM updating procedure was performed by minimizing the difference between experimental and analytical modal properties. Afterwards, seismic performance assessment of a representative bridge was carried out using ANSYS software. Two different nonlinear approaches were considered, namely, pushover and nonlinear time history (NLTH) analyses. In the analyses, macro-modeling approach was followed to develop homogenized behavior of stone and mortar. It was found that mass proportional pushover analysis gave similar results to NLTH in terms of seismic performance. The other significant point was that modeling soil medium reflects the actual behavior of the bridge in the sense that artificial stress concentrations do not occur at the pier base. It was also observed that tensile strength capacity was reached on spandrel walls which may result in a probable failure.

KEYWORDS:

• Stone arch bridges
• system identification
• FEM updating
• seismic assessment

Acknowledgments

Authors are grateful to Ministry of Transportation, Maritime and Communications and General Directorate of Turkish State Railways for their collaboration.