Evaluation Research Of Existing Multi-span Concrete Continuous Beam Bridge Vehicle Load Effect

Vehicle load is one of the most important design load for bridge structure. With the phenomenon of vehicle overloading worsening, the safety of the existing bridge faces enormous challenges. This paper takes a multi-span concrete continuous beam bridge-Aofeng Bridge in Fuzhou as engineering background, in order to improve the assessment of the vehicle load effect of this bridge, help to ensure the security of bridge structure and decide the strategy of maintenance and strengthening scientifically, the primary tasks of this paper are as follows:(1) On the basis of the ambient vibration testing, the single objective function based on frequency is used to update the bridge finite element model so as to establish the baseline finite element model for the purpose of follow-up assessment.(2) According to the existing traffic survey information, with the probability of specific vehicle convoy passing the bridge based on equilibrium renewal stochastic process, probability density function of the total weight of vehicle convoy and maximum data points of influence line area under the vehicle convoy, the vehicle load model is established, and the maximum probability distributions of vehicle load effect of different assessment reference period under the normal and abnormal operation state are obtained, then an evaluation of the distributions in comparison with the design load effect as well as the specification limit is conducted.(3) By using the IBIS-S monitoring system to monitor effects and comparing the fitting maximum probability density function and distribution function of the measured effects with the above theoretical probability density function and distribution function, the vehicle load model is verified. Maximum probability distributions of measured effects of different assessment reference period are evaluated comparatively with the design load effect and theoretical evaluation results.The research results are listed in the following:(1) The single objective function based on frequency can be used to finite element model updating, the calculated frequencies from finite element model after updating agree well with measured frequencies and theoretical calculation results of dynamic characteristics are greatly improved.(2) The maximum probability distributions of vehicle load effect of different assessment reference period are as the law of extreme value type I distribution, and 0.95 quantiles of the distributions don’t exceed the design load effect and the specification limit, bridge can meet the deformation requirement of serviceability limit state during re-service period. When considering abnormal operation state, under certain damage and overloading conditions, the 0.95 quantiles will exceed the design load effect, but always satisfy the code requirement.(3) The existing monitor data shows that the maximum probability distributions of measured effects obey normal distribution and bridge can meet the deformation requirement of serviceability limit state during re-service period. Combined with the contrast results of the theoretical and measured tail distribution, applying equilibrium renewal stochastic process to acquire the tail quantile of effect distribution is rational to some extent.