Simulation and analysis of girder end longitudinal motion for suspension bridges considering multiple resistances using on-site vehicle load sequences

Abstract

Under repeated girder end displacements, various forms of damage and deterioration occur in the girder end restraining devices, leading to their premature failure. To understand the inner law of the longitudinal girder end motion, a model development and updating method is proposed for suspension bridges considering multiple types of restraints by using on-site vehicle load sequences. In addition, key parameters associated with the longitudinal girder end motion are discussed based on the updated model. First, the on-site vehicle load sequences are generated based on the vehicle weighing and video systems, and the corresponding input loads for numerical simulation are obtained using the virtual work principle and shape functions. Then, an initial finite element model of a suspension bridge is developed considering the resistances of the expansion joints etc. Transient dynamic analysis is used to calculate the time history of the girder end displacement under the on-site vehicle load sequences. Subsequently, the longitudinal resistance parameters, for example, the spring stiffness, are selected as optimized variables, where the genetic algorithm is used to achieve the optimal values. Finally, the characteristics of the displacement at the girder end are examined in the context of the varying volume of traffic and proportions of heavy vehicles using the updated finite element model. As a result, the optimal spring stiffness, damping coefficient, and frictional force are 14,563.5 kN/m, 654,371 $\mathrm{N}·\mathrm{S}·m^{-1}$ and 0.0330256, respectively. Simulation results reveal that increases in both traffic volume and heavy vehicle proportion lead to greater cumulative girder end displacements, with the latter playing a dominant role in amplifying displacement magnitudes.