Study On Simplified Model Of Partially Concrete-filled Steel Tubular(PCFST) Piers Subjected To Vehicle Collisions

In recent years,there are many accidents of vehicle collision with various kinds of bridges and piers,and the research on this kind of collision has gradually attracted the attention of scholars.In this paper,the problem of Partially Concrete-filled Steel Tubular（PCFST）Piers subjected to vehicle collisions is studied based on LS-DYNA finite element analysis（FEA）software,further improves the simplified model of vehicle,and provides theoretical support for the design of bridge pier against vehicle impact.（1）On the problem of small vehicles impacting on piers,the simplified vehicle model（SVM）and refined vehicle model（RVM）are established respectively.It is found that taking the finite value of K₂ in the spring stiffness curve of SVM can more accurately simulate the response of RVM model impacting on bridge piers than the infinite value.In order to facilitate the calculation of K₂,the SVM stiffness amplification factor is introduced.Considering the frontal impact and 45°angle impact,the influence of relevant parameters on the value of the SVM stiffness amplification factor is studied,and the calculation formula of the SVM stiffness amplification factor is derived.The formula and its derivation process provide methods and ideas for using SVM to better analyze vehicle-pier impact problem.（2）On the problem of truck impacting on bridge pier,it is found that the Equivalent Truck Frame Model（ETFM）can simulate the response of F800 impacting bridge pier more accurately by increasing the limit deformation of deformation energy dissipation structure to 2800 mm and considering the impact of the geometric size of the impacted object on the limit internal energy of truck extrusion.Through parameter analysis,it is found that the ETFM can still simulate the response caused by F800 impacting the bridge pier after changing the concrete filling rate,initial impact velocity,truck mass and pier axial compression ratio,especially simulate impact impulse and truck internal energy more accurately.（3）The simplified vehicle model is compared with the results of rigid punch impact on bridge pier.The response includes deformation mode,impact force,displacement and energy relationship.The results show that it is safe to use rigid punch instead of actual vehicle to study the anti-collision performance of the pier.From the point of view of energy,the safety factor of the rigid punch compared with the simplified vehicle model is proposed.Through using the research results of this paper,the method of using SVM and ETFM to evaluate the impact effect of the rigid punch is obtained.