Dynamic Response And Probabilistic Demand Analysis Of RC Bridge Piers Under Vehicle Impact

In recent years,the sustained growth in world economy leads to the demand for infrastructure construction,and reinforced concrete(RC)structures have been employed extensively in actual projects due to their good stability and practicality.In such a general environment,RC structures while greatly contributing to the improvement of human living standards,its safety performance,especially the anti-collision performance,has received more and more attention.Especially in bridge structures,bridge pier columns are subjected to lateral impact in all directions in addition to the loading effect of the superstructure.In the past decades,bridge piers have been impacted by vehicles,scientists have carried out a lot of research in the field of vehicle impact on bridge piers,however,the existing research is still not in-depth analysis of the mechanism and dynamic response of RC piers under vehicle impact.Accordingly,the dynamic response of RC piers under vehicle impact,simplified analysis methods and probabilistic demand analysis are investigated in this paper by means of experiments,finite element analysis and theoretical analysis.The major achievements and conclusions are listed below:(1)The lateral impact test of the slide model vehicle of the full-scale RC bridge pier is carried out.For the complete full-scale RC bridge pier column left by the subject group in the previous test,the slide acceleration device and rigid model vehicle are designed and manufactured independently to conduct multiple impact tests on the full-scale RC column.The test obtain the impact force,lateral displacement and acceleration of the RC column,steel strain,vehicle acceleration and image data of the whole impact process.Through the analysis of the above test data,the results show that: the pier gradually appear horizontal bending cracks above and below the impact point and shear diagonal cracks below the impact point under multiple collisions,and eventually the shear diagonal cracks become the main cracks.(2)A refined finite element model of the full-scale RC column for vehicle collision was established.In order to realistically simulate the damage and response behavior of RC piers under multiple collisions,the simulation methods of continuous collision and single collision are proposed in this paper,and the results of each of the two methods are compared.The simulation showed that the finite element model(FEM)developed by this paper can generally simulate the damage pattern,peak forward displacement and self-oscillation period of the RC pier under multiple consecutive collisions more accurately.However,the K&C material model(with default parameters)used in the continuous collision simulation is not accurate enough to simulate the local impact damage of concrete,resulting in a large difference between the results of impact force in the continuous collision simulation and the test results and the single collision simulation;in addition,the material model is not accurate enough to simulate the crack closure behavior of concrete,resulting in a large difference between the simulation results of reverse displacement of the pier under impact and the test results.(3)Through the analysis of three existing finite element vehicle models,a general simplified mechanical model of vehicle impact on bridge piers is established.Finite element analysis found that the three types of vehicles impact the bridge pier have similar mechanism of action and mechanical characteristics,based on which the general mechanical model framework of the three types of vehicles is proposed,and the values of the parameters in the framework are explained.Moreover,in considering the validity of the proposed simplified model,it was compared with the rigid and elastic bridge pier simulations,and the results showed that: the proposed simplified mechanical model can match well with the rigid impact forces simulated by the vehicle finite element;when the simplified mechanical model is coupled with the beam unit elastic bridge pier,the specific values of the relevant vehicle impact-related strength parameters and structural response parameters can be calculated quickly,and the obtained results are in good agreement with the refined finite element analysis.(4)For the probabilistic demand analysis in earthquake engineering,a probabilistic demand model for vehicle impact on bridge piers is established and a fast calculation method for vehicle impact on bridge pier response is proposed.Referring to the idea of seismic demand analysis in earthquake engineering,the probabilistic demand model of vehicle impact on bridge pier is established by considering the applicability of vehicle impact intensity measures and structural response parameters through the index evaluation system of ground vibration strength parameters in earthquake engineering.The established vehicle demand model can well satisfy the log-linear relationship,which proves the reasonableness of the assumption.Lastly,base on the findings of the research group,a fast calculation method of the vehicle impact response is proposed,which can quickly solve the bottom shear response of the vehicle impacting the bridge pier.