Study On Damage And Protection Of Double-column Pier Bridge In Western Mountainous Area Impacted By Rockfall

In recent years,one has been developing the one’s own economy and one’s own “one belt,one road” strategy.However,due to the abundant rainfall in the west of China,it is the source of many rivers,and the large and high mountains on the banks of the suspended rivers in this area,with steep cliffs,are very prone to landslide,debris flow,collapse and rockfall and other geological disasters.Therefore,in the western mountainous area of China,the highway along the valley often has rockfall impact on the bridge,which greatly affects the daily operation and maintenance of the mountain bridge.At present,rockfall and bridge collision has become a key link in bridge planning in mountainous areas.Due to the high cost of rockfall impact test,there are only a few full-scale rockfall bridge impact tests at present.Some scholars adopted simplified scale model or equivalent rockfall model to carry out experimental study.Most researchers mainly use the finite element method to study the problems of falling rocks and bridges.Generally speaking,because the problem of Falling Rock and bridge collision is more complex,and most researchers have not selected enough parameters in the analysis process,the impact position of rockfall,reinforcement ratio of bridge pier and axial compression ratio are not analyzed comprehensively,which is worth further study.In this paper,a bridge in the west of China is taken as the research object,and the nonlinear contact finite element method is used to study the dynamic response,damage law and failure form of the bridge under the impact of falling rocks,based on the research results,a safer and more economical protective device is explored.The main research contents are as follows:1.First of all,this paper summarizes the numerous bridges in western China,then the frequent geological activities in western mountain areas,and then collates the cases of large-scale rockfall disasters in China.It is found that most of them occur in Western mountain areas of China,this leads to the research background and significance of the paper.This paper introduces and analyzes the general situation of research on rockfall at home and abroad,including research on rockfall impact force,rockfall disaster risk,dynamic response and damage of bridge pier under rockfall impact,and protection measures against rockfall impact.Then the LS-DYNA program and the nonlinear contact finite element method theory are introduced in detail and the material constitutive equation involved in this paper is introduced in detail.2.The numerical simulation method is validated based on the impact test of reinforced concrete beam,and the finite element model material and contact algorithm are verified by the energy conservation theorem.Then,based on the theory of nonlinear contact finite element method,the finite element numerical model involved in this paper is established.3.Based on a two-column bridge in western mountainous area,a high-precision three-dimensional solid impact finite element model is established by Ls/dyna,and the influence of rockfall parameters on dynamic response and damage of the bridge is analyzed,the impact force time-history curve of bridge pier is compared with the equivalent impact force formula given by various national codes.4.Based on the basic theory of structural dynamics,a high-precision finite element model of rockfall-bridge collision is established,and the whole process of bridge collapse is simulated by ANSYS/LS-DYNA.The failure process and collapse mode of the bridge under different parameters are compared,and the failure mode and vulnerable position of the bridge pier under the impact of high energy rockfall are analyzed.5.A three-dimensional nonlinear simulation model considering the diameter,impact velocity,impact position,reinforcement ratio and axial compression ratio of piers is established.Under the influence of different parameters,the influence mechanism and damage evolution rule of rockfall impact on bridge pier are studied.6.Four kinds of common anti-collision facilities for bridge piers are introduced in detail,and then the collision analysis of three kinds of common anti-collision facilities is carried out.Finally,four kinds of anti-collision facilities and the situation of no protection are compared and analyzed,and the displacement and damage volume of pier top under five working conditions are analyzed.