Seismic Response Analysis Of CFST Stiff-Skeleton Arch Bridge And Study On Bearing Capacity Of Its Component

CFST stiff-skeleton arch bridge is a bridge structure that formed by the application of steel tubes filling and outsourcing concrete structure in the arch bridge.The excellent mechanical properties and construction technology have made some successful cases of its application in the highway engineering in our country,and the application in Railway Engineering in our country is still less,research object is limited,the results are not many.Meanwhile,the design content of the steel tubes filling and outsourcing concrete structure is not yet appeared in China's Present railway engineering specifications.Therefore,exploring its structural response under earthquake and whether it has reached its ultimate bearing capacity,providing reference for seismic design and structural design for the construction of more railway bridges of this type in the future becomes very important and very necessary.In this paper,seismic response analysis and bearing capacity study were proceed relied on an extra-long span CFST stiff-skeleton arch bridge in the construction of Chongqing Guizhou Railway,the main research contents are as follows:(1)After an overview of the theory of dynamic characteristics,model building and the analysis of natural vibration characteristics of the bridge were proceed by the finite element program MIDAS.(2)The seismic response of the bridge under the action of the standard design response spectrum was analyzed.At the same time,the internal force of the structure and the stress of component under the action of dead load,train load and temperature load were also analyzed.(3)The time history response of the bridge under the action of E1-centro seismic wave and Wenchuan Wolong seismic wave was analyzed.The calculation results of the two methods are compared and analyzed,and the influence of traveling wave effect on the bridge was also analyzed.(4)The force conditions of outsourcing concrete,filling concrete and steel pipe were analyzed.According to the allowable stress method used in Railway Engineering,the stress state of each material was judged.(5)The most disadvantageous section of actual stress of the bridge structure was determined,and was constructed as steel tubes filling and outsourcing concrete short column.Based on ANSYS,this thesis built the model of the complement and figured out the complement's ultimate bearing capacity and safety factor under vault practical internal force conditions of this bridge structure.Comprehensive results of this analysis,we can see:The first order frequency of the main beam is 0.652 Hz,the fundamental frequency of the whole bridge is 0.593 Hz,they have little difference,it shows the stiffness of main beams is relatively large;the bandwidth of the first 15 order natural frequencies of the bridge is 1.466 Hz,it shows the vibration of this bridge is intensive;response spectrum analysis and time-history analysis show that the seismic performance of the bridge is good,the calculation results of the two methods are not quite different,and have the same patterns and trends,consider traveling wave effect on the bridge forces is unfavorable,and along the bridge to the traveling wave effect is greater than the transverse traveling wave effect;the stresses of outsourcing concrete,filling concrete and steel pipe under various loads are within the scope of the material allowable stress,the structural stree is in a safe state;the most disadvantageous section of actual stress of the bridge structure is the crown section,which has good stress state under various loads,and the value of its internal force is much less than its ultimate bearing capacity,so it can be considered that this kind of CFST stiff-skeleton arch bridge has high bearing capacity and good structural safety.