Analysis Of Mechanical Behavior And Dynamic Response Of Long-span Concrete-filled Steel Tube Arch Bridge After Cavitation

Concrete-filled steel tube structure not only has the advantages of both steel tube and concrete,but also improves the stability and corrosion resistance of steel tube as well as the compressive performance of concrete,so the composite structure has the advantages of high bearing capacity and good durability.With the above characteristics,concrete-filled steel tube structure is widely used in the construction process of arch bridge,but for in-service concrete-filled steel tube arch bridge,due to its own structure and external factors and other reasons,concrete-filled steel tube with arch ribs will mostly occur void disease.Therefore,taking Tuzha Bridge as the engineering background,this paper studies the influence of arch rib void on the mechanical performance and dynamic response of concrete-filled steel tubular arch bridge.the main research contents and results are as follows:(1)Firstly,the material constitutive relation is introduced,including the unified theoretical constitutive relation of concrete filled steel tube,the constitutive relation of secondary plastic flow of steel tube and the constitutive relation of core concrete considering hoop effect.Among them,the load eccentricity and void rate reduction coefficient are introduced into the hoop coefficient.On the basis of verifying the correctness of the constitutive relation and modeling method,the effects of concrete void ratio of arch rib core and steel content of concrete filled steel tube on the stiffness of concrete filled steel tube arch ribs and the ultimate bearing capacity of the whole bridge are discussed.the influence of the void position of arch ribs and the mode of load on the ultimate bearing capacity of the whole bridge is also considered,which has a certain practical value forjudging the bearing capacity of concrete-filled steel tubular arch bridge during operation.(2)Based on the unified theoretical constitutive relation of concrete filled steel tube,the finite element analysis model of complete bonding of arch ribs is established,and the changes of first-order vibration modes and frequencies of in-plane and out-of-plane of concrete-filled steel tubular arch bridges are compared between complete bonding and complete debonding.In-plane mode is more affected by the bonding state of arch ribs than out-of-plane.(3)The general vehicle-bridge coupling vibration equation is established,and the code for solving the vehicle-bridge coupling vibration equation is compiled by Newmark-βiterative method combined with MATLAB,and four kinds of bridge deck irregularity grades are generated according to the trigonometric series method combined with MATLAB,based on which the dynamic responses of bridges and vehicles are analyzed.(4)According to the different bonding states of concrete-filled steel tubular arch ribs,the effects of bridge deck irregularity and vehicle speed on the dynamic response of the bridge at the middle of the bridge span and at the position of L/4 are analyzed.The impact coefficients of the bridges obtained by dynamic responses are compared with those obtained by different codes,which provides a certain reference for the value of impact coefficients of this kind of bridges.(5)According to the different bonding states of concrete filled steel tubular arch ribs,the effects of bridge deck irregularity,vehicle speed and vehicle load on vehicle dynamic response are analyzed,which provides some reference for the limitation of vehicle speed and vehicle weight when crossing the bridge.