Analysis Of Vehicle-pier Collision Based On LS-DYNA And Pier Reliability Research

In the process of daily transportation,the vehicle-pier collision accidents occur from time to time.Obviously,the structural reliability and operational life span of the bridge will be impacted to a certain degree after the vehicle collision.Therefore,it is of great significance to calculate the collision force accurately to master the effect imposed on the bridge from the damage after the collision and study the reliability of bridge under vehicle impact with the theory of reliability systematically both in theory and in practical application field.The primary work of this dissertation can be summarized as follows:(1)The FE model of vehicle-pier collision was established.The selection of material model,the definition of contact algorithm,the control of hourglass phenomenon,the division of mesh and the processing of boundary conditions were mainly studied.It proved the method of building model in the dissertation was correct and reliable,when the results of the FE simulation analysis comparing with the related literatures.The development rules of stress was studied by simulating a typical condition and it showed the shear failure was easy to occur in the impacted areas of pier while the bending failure was easy to occur in the bottom of pier.(2)On the basis of FE model of vehicle-pier collision,the method of calculating the equivalent static force corresponding to the vehicle impact force was firstly introduced,then the sensitivity analysis was conducted to find main factors about the vehicle-pier collision force.A series of samples were provided to build artificial neural network through a series of simulation conditions.Finally,a simple calculation formula was derived and compared with domestic and foreign specifications.(3)The reliability of RC columns subjected to centroid vehicle collision was studied based on the stochastic finite element method and the theory of structural reliability: the probabilistic model of column subjected to vehicle collisions was established,considering the effect of vehicle impacting.Then,a research about probability distribution for the bearing capacity in key section of the column including shear and bending and the column’s response with the collision force was made,using the method of the Latin hypercube sampling.Finally,the substructure of bridge was regarded as serial system and the method of design verification points was used to analyze the reliability.The reliability index of the column under vehicle impacting in the lateral and longitudinal direction of bridge was utilized to calculate the systemic failure probability.It proved the internal force in key section of the column under vehicle colliding followed the normal distribution and the shear failure was easy to occur,no matter under the effect of vehicle collision in the lateral direction of bridge or in the longitudinal direction of bridge.(4)Based on the theory of structural reliability,the reliability index of shear bearing capacity of column under vehicle impacting in the longitudinal direction of bridge was set as the control objective to investigate the sensitivity of relative variables.It indicated that the sensitivity to the reliability index of shear bearing capacity of column were the compressive strength of concrete,yield strength of stirrup,ring diameter of stirrup,stirrup spacing and bulk density of concrete.Comparing with the mean value,the change of coefficient of variation had much less influence on the reliability index among the random variables influencing the shear capacity.Among them,the coefficient of variation for the strength of concrete had more influence on the sensitivity to the reliability index of shear bearing capacity compared with the other random variables.