Evaluation of bridge load carrying capacity using updated finite element model and nonlinear analysis

The integrity of ageing bridges is in doubt because of increasing traffic loads, deterioration of materials, possible damage during service, and revised code requirements. Traditional methods in prediction of load varying capacity of bridges are usually based on the design blueprints and may not reflect the bridge condition as is. In this paper, the nonlinear finite element analysis, incorporating the model updating technique, is used to predict the behaviour of a 30-year-old slab-girder bridge. The original finite element model based on the design drawings is updated by modifying the stiffness parameters of the girders, slab, shear connectors and bearings so that the vibration properties of the model match the field vibration measurement data. The updated model represents the present condition of the bridge better than the original model that is based on the design blueprints. The load carrying capacity of the bridge is then calculated using the original and updated finite element models, respectively, with consideration of nonlinear material properties. The comparison shows that the bridge load carrying capacity under the present condition is lower than that under the design condition, whereas is still above the design requirement. The influence of the shear connectors on the load carrying capacity is specially investigated.