Seismic Response Analysis And Seismic Isolation Technology Research Of Long-span Concrete-Filled Steel Tubular Arch Bridge

Since the beginning of the new century,the state has made great efforts to build infrastructure projects.Under the background of the national vigorous promotion of the overall transportation network planning,the bridge structure forms keep pace with the times and are widely used.The concrete-filled steel tube arch bridge is widely used because of the advantages provided by its material combination and beautiful structural form.Because of the perfect fusion of steel tube and concrete,the core concrete is wrapped with steel tube to make the core concrete more compact,and the core concrete can improve the stability of the steel tube and make the span of the arch bridge larger and larger.In the past decade,with people’s increasing expectations for a better life and the country’s higher requirements for social stability,concrete-filled steel tubular arch Bridges have gradually developed towards a trend of smaller width-span ratio and larger frame-span ratio.However,the plate movement has become more and more severe,and the number of earthquakes and seismic intensity have increased,making the bridge in the construction process.Therefore,it is of great significance to study the seismic response of CFST arch Bridges under construction or in service as well as the effect of seismic isolation devices.Based on Tuzha Bridge in Baojing County,Xiangxi Tujia and Miao Autonomous Prefecture,the following work has been done:(1)Review the development history of concrete-filled steel tubular arch Bridges,introduce the development situation of concrete-filled steel tubular arch Bridges at home and abroad,and introduce the main research content of this paper by combing the research status of seismic response of concrete-filled steel tubular arch Bridges.Since the foundation of the subsequent analysis is the finite element model of Tuzha Super large bridge established by the general finite element software Midas/Civil,Therefore,the basic finite element method and seismic analysis method are briefly introduced,and the basic meaning and equation of natural vibration characteristic analysis theory are introduced.The dynamic characteristics of the bridge are calculated and analyzed.It is known that the bridge has a small fundamental frequency and the first mode of vibration is transverse bending of the arch beam;The transverse stiffness is weak,and the bending deformation of the columns on the arch does not occur until the sixth stage,indicating that the columns on the arch of the bridge have good stability and can play a good role in connecting the preceding and the following.(2)Using the response spectrum method and time history analysis method to calculate the bridge seismic response results,the location of the record data unified selected downstream of the arch rib inside bottom chord as record object,considering the consistent excitation,the uniform excitation and traveling wave effect on the impact of the seismic response of the bridge,and analysis of the response spectrum method and input Taft classic under the seismic time history analysis method of seismic response results.The results of the two seismic analysis methods show that the lateral displacement is much less affected by the seismic load along the bridge than the longitudinal displacement and vertical displacement,and the axial force is the most affected by the internal force,followed by the vertical moment and the transverse moment.The transverse shear force at the arch foot is larger than that at the rest of the main arch ring.When the transverse displacement is affected by the transverse bridge earthquake,the seismic effect is the largest,and the axial force is the most affected internal force.The influence of the vertical displacement on the displacement of the vertical bridge is small,and the influence of the vertical displacement on the displacement of the three bridge directions is larger.The axial force is the most affected internal force,so it can be seen that the axial force is the most affected under any earthquake load.In cis,horizontal,vertical three bridge under the seismic wave input,comparing the calculation results of two methods,the results from different seismic wave to the bridge is not consistent,along the bridge seismic response to the earthquake under the action of both results close to the earthquake response of the transverse bridge to the earthquake under the action of the former result is greater than the latter,vertical bridge seismic response to the earthquake under the action of the latter result is greater than the former.(3)The influence of traveling wave effect on structural seismic response is closely related to seismic wave velocity,and the change of wave velocity will greatly affect the internal force and displacement of the bridge structure;Compared with the structural response of the bridge under the uniform excitation,it can be concluded that under the influence of the traveling wave effect,the displacement of the bridge structure in the vertical and vertical directions increases greatly,except the axial force,transverse shear force and vertical bending moment decrease,the vertical shear force,torque and transverse bending moment all increase greatly.When the bridge span is constant,the wave velocity determines the time hysteresis effect of the structure.(4)The working principle of several commonly used seismic isolation devices is briefly introduced,and the seismic performance of the two kinds of commonly used seismic isolation devices on the bridge is analyzed,and the vibration isolation effects of the two are compared and analyzed.The effect of lead core seismic isolation rubber bearings and friction pendulum seismic isolation bearings on the displacement isolation of the bridge is not obvious.The lead core isolation rubber bearing has better isolation effect on internal force,and the static performance of lead core isolation rubber bearing is better.The overall period of the friction pendulum isolation bearing and the bridge structure is larger than that of the lead core isolation rubber bearing and the bridge,so the friction pendulum isolation bearing is better in terms of dynamic performance.