Stiffness Identification of Truss Joints of the Nam O Bridge Based on Vibration Measurements and Model Updating

This paper presents an approach for stiffness identification of node joints of a large-scale truss bridge (Nam O Bridge in Vietnam) based on vibration measurements and model updating. Vibrations are recorded under ambient conditions using piezoelectric sensors. Excitation is due to wind, micro-tremors, or train passage. From these vibrations, modal parameters are extracted. Modal analysis is also performed using a finite element model created in MATLAB. Afterwards, model updating is applied to minimize the discrepancy between numerical and experimental modal analysis results. Evolutionary algorithm such as particle swarm optimization (PSO) based on a global search technique is employed. Three scenarios of boundary conditions of truss joints (pin, rigid, and semi-rigid) are considered. The result of model updating shows that semi-rigid (using rotational springs) joint conditions represents correctly the dynamic behavior of the considered bridge.