Numerical Simulation Research On Static And Seismic Performance Of Bifurcated And Separated Special-shaped Concrete Box Girder Bridge Structure

With the rapid development of China’s national economy and the rapid development of infrastructure in China’s transportation industry,bridges are an important part of transportation infrastructure.The static performance of the superstructure and the seismic performance of the substructure directly affect the use and working performance of the bridge,and determine whether the bridge can continue and reliably contribute to economic construction.In the existing bridges,the bridge structure of the transition part of the main line bridge and the ramp bridge should be more bifurcated special-shaped bridge.As an important part of the transition part,the static performance of the bifurcated special-shaped bridge structure in the ultimate state of the bearing capacity and the ultimate state of the normal serviceability under the persistent condition plays a decisive role.By using the existing finite element software to establish the finite element model of the bifurcated special-shaped bridge,it is of great significance to carry out accurate simulation of its construction and operation process,which can provide a basis for the static performance evaluation of the bifurcated special-shaped bridge structure under various limit states.Under seismic load,the bridge structure is subjected to the reinforcement of reciprocating load,and its weak parts are mainly concentrated in the lower structure.Under the action of reciprocating load,the stress of the longitudinal reinforcement at the bottom and top of the pier of the substructure of the bridge increases rapidly,and the tensile and compressive damage of the pier increases rapidly.The weak parts of the bridge gradually develop into plastic hinges.Based on this,the static load of the bridge substructure or structural components is applied to repeatedly load and unload the bridge substructure or structural components in both positive and negative directions,so as to simulate the stress characteristics and deformation characteristics of the bridge substructure in the reciprocating vibration under earthquake.The effect of structural vibration is obtained by static method,so as to obtain the hysteresis curve,skeleton curve and various seismic performance indexes,so as to evaluate the seismic performance of the bridge substructure under low cyclic loading,and provide the basis for the seismic design of the bridge substructure.Based on the design drawings of the bifurcated special-shaped concrete box girder bridge,this thesis uses Midas/Civil finite element software to establish the finite element model of the bifurcated special-shaped concrete continuous box girder bridge.According to the load and support constraints of the bifurcated special-shaped concrete box girder bridge in the construction and operation process,the construction and operation process of the bifurcated special-shaped concrete box girder bridge is more realistic and accurate simulated by adjusting the degree of freedom of the finite element model nodes and imposing loads on the corresponding nodes and units.Based on ABAQUS finite element analysis software,a full-scale finite element model of the substructure of the bifurcated special-shaped concrete box girder bridge is established.By applying the established low-cycle reciprocating load on it,the hysteretic curve,skeleton curve,energy dissipation curve,stiffness degradation curve,residual displacement curve and failure pattern cloud of the substructure of the bifurcated special-shaped concrete box girder bridge are obtained.By analyzing the development trend of different seismic performance indexes,curves,curve shape and failure pattern cloud,the seismic performance of the substructure of the bifurcated special-shaped concrete box girder bridge is studied.Under the action of reciprocating load,the hysteretic curve of the substructure of the bifurcated special-shaped concrete box girder bridge is relatively full,showing a relatively obvious bow shape,strong horizontal bearing capacity,and good energy dissipation capacity.The overall stiffness degradation trend is normal,and the residual displacement of the pier is large,and the deformation capacity is strong.Based on the full-scale finite element model of the substructure of the bifurcated special-shaped concrete box girder bridge,the ABAQUS finite element analysis software is used to analyze the axial compression ratio,the equivalent strength replacement of longitudinal reinforcement and the volume replacement of longitudinal reinforcement.By applying the same low-cycle reciprocating load to the finite element model of the substructure of the bifurcation separated-separated special-shaped concrete box girder bridge with different parameters,the hysteresis curve,skeleton curve,energy dissipation curve,stiffness degradation curve,residual displacement curve and failure pattern cloud chart of the substructure of the bridge under different parameters are obtained.Under reciprocating load,with the increase of axial compression ratio and longitudinal reinforcement strength,the horizontal bearing capacity of the lower structure of the bifurcated special-shaped concrete box girder bridge increases significantly,the energy dissipation capacity increases slightly,the residual displacement increases slightly,the deformation capacity increases continuously,the overall tensile and compressive damage of the pier decreases slightly,and the damage range decreases slightly.