Structural safety assessment of bowstring type RC arch bridges using ambient vibration testing and finite element model calibration

The structural safety evaluation of a bowstring type reinforced concrete (RC) arch bridge was investigated by ambient vibration testing and finite element model calibration in this study. The bridge named as Ali Çetinkaya Bridge in Samsun, Turkey, was selected for this investigation. The bridge constructed in 1937 consists of the seven discrete arches and its total length is approximately 250 m. The bridge damaged by environmental effects and it was closed to the traffic loads. The presented study consists of four main parts: ambient vibration test, initial finite element modeling, finite element model calibration and structural analysis of the calibrated finite element model. The ambient vibration tests were performed using Operational Modal Analysis Method under the wind, human and water flow loads to identify the actual natural dynamic parameters, such as the natural frequencies and mode shapes, modal damping ratios. Enhanced Frequency Domain Decomposition and Stochastic Subspace Identification methods were used to extract the experimental dynamic characteristics. The initial finite element model was developed by including the soil effects in SAP2000 program to obtain the analytical dynamic characteristics. In the initial finite element model, the beam, plane and solid elements were used. After that, the initial finite element model was calibrated according to the ambient vibration test results considering the material properties and boundary sections as variable parameters. The calibrated model assumed to reflect the current state of the bowstring bridge was analyzed under dead, moving, traffic, water and earthquake loads. The maximum displacements, tensile stress, compressive stress and shear stress were attained each case and compared with each other.