Dynamic Response Analysis Of Superstructure Of Steel-concrete Composite Beam Bridge In Rockfalls Impact

Rockfall disasters are the most common natural disasters,which occur quite frequently during the rainy season in mountain areas.Since the implementation of "The great western development strategy",both expressways and railway networks have entered remote mountainous areas,and bridges on lines have been increasingly hit by Rockfalls.Once the bridge on the traffic line is hit by rockfall,it will directly affect the operation of the relevant traffic line and the normal production and life of local residents,and cause huge economic losses.The steel-concrete composite beam bridge has been developed in recent years,and it has been accepted by many designers because of its own advantages.Therefore,the research on the superstructure of steelconcrete composite beam bridge has some engineering significance.The paper takes a steel-concrete composite beam bridge as an example,uses explicit dynamic analysis methods,studies the dynamic response of steel-concrete composite beam bridge superstructure under rockfall impact,analyzes the stress situation of bridge deck and I-beam under different influencing factors.The main research contents of the paper are as follows:(1)The severity of the rockfall disaster was explained through statistics and examples,and the significance and necessity of this study wes clarified;the current research status of rockfall movement characteristics and rockfall impact at home and abroad was analysed.(2)The four typical movement forms of falling stones during the falling process was summarized,and the movement formulas of the four movement forms according to the principles of kinematics and dynamics was derived;the rockfall trajectory analysis software was introduced and it was used to investigate the rockfall movement trajectory of a high-risk slope,and obtain the rockfall movement trajectory and speed variation law;the existing calculation methods of rockfall impact force was summarized,the finite element method was selected as the calculation method in this paper.(3)The types of elements,the material constitutive models of four materials(concrete,steel,ordinary steel bars,falling rocks),the mesh division,the types of contact between components,and the evaluation of the stability of the results which is used in the model modeling process of this paper were described in detail to ensure the accuracy of the model calculation results.(4)The two positions of the steel-concrete composite beam bridge(the center of the deck and the top of the I-shaped steel beam)were numerically simulated.The dynamic response of the superstructure of the steel-concrete composite beam was analyzed from the aspects of impact velocity,impact area,and quality of rockfall;and the relevant laws of dynamic response of steel-concrete composite beam bridges under falling rock impact was summarized.