Research on the finite element simulation of and updating method for old riveted truss bridges

Finite element modelling to establish the actual mechanical performance of very old riveted truss bridges with complex configurations is essential for the sake of accurately assessing their remaining service life and their safety. This paper describes a study on finite element simulation and its updating for the 104-year-old Waibaidu Bridge in Shanghai. First of all, a solution is proposed for structural simulation problems as the shear deformation of built-up members, gusset plate rigid field and relevant cracks as well as the concrete slab's composite action. The area loss of the main truss members and the actual effective width of the concrete slab are identified as key factors after error analysis for actual performance modelling, considering several causes such as second-order effects, shear deformation, corrosion and the composite action of the concrete slab. Afterwards, the dual-stage model updating method is tailored to old riveted truss bridges, which modifies structural stiffness through static load testing in the first step and then calibrates mass distribution through vibration testing. The research shows that: 1) dual-stage finite element simulation is effective; 2) the shear deformation effect should be taken into consideration for latticed members, and the influence of second-order effects and shear deformation should be also taken into account when bridge lateral response is involved, while the errors of composite parameters of concrete slab can never be neglected; and 3) corrosion modelling for truss members and crack monitoring for gusset plates have little significance on the finite element simulation and updating of old riveted truss bridges.