The Research On Key Technologies Of Seismic Suspension Bridge In High Intensity Earthquake Area

At present,there are few suspension Bridges built in high intensity earthquake area,however,because of its superior crossing performance,there are more and more suspension Bridges will be built in high-intensity areas,such as mountain areas.Therefore,it is significantly important to study the earthquake proofing technique of long-span suspension bridge in high intensity earthquake zone.This study is based on the engineering background of suspension bridge on a large highway and we use the response spectrum and nonlinear timepath analysis on the basis of comparative study of seismic response of high intensity seismic region to emphatically study the seismic mitigation measures of long-span suspension Bridges under the background of different design parameters of different central buckles and viscous dampers and different bridge towers so that we can provide reference for seismic design and analysis of large span suspension Bridges in high intensity seismic zone.The following are the main research contents of this study:(1)Firstly,we study the establishment and the analysis about dynamic characteristics of the finite element model of long-span suspension bridge.According to the structure design parameters of the bridge,we use the Midas Civil platform to establish the spatial finite element model and the multiple Ritz vector iteration method to calculate the modal parameters of the bridge.The results show that the long-span suspension bridge has some wonderful characteristics such as small vibration frequency and a long basic period,which is consistent with the trait of the general suspension bridge,that is,the Flexibility.(2)We secondly study the seismic response analysis of long-span suspension Bridges.According to the seismic parameters of seismic report,we use the response spectrum and nonlinear time analysis method respectively to comparatively analyze the seismic response of the structure with E1 and E2 earthquakes.The results demonstrate the significant difference of the seismic response of the bridge tower and the main girder under the effect of longitudinal and transverse earthquakes and the consistence of the seismic response of the bridge tower under E1 and E2.Because of the strong nonlinearity of suspension bridge,we consider more nonlinear factors for the nonlinear time analysis.Therefore,it is recommended to use nonlinear time analysis to calculate the structure of large span suspension Bridges in high intensity seismic zones.(3)Subsequently,we study the seismic response of suspension Bridges with different central clasps.We set up three different forms of central buckle in the mainspan span cable – beam to compare the influence to the suspension bridge' s displacement of the stiffening girder,internal force and displacement of the main tower and Stiffening beam stress produced by those forms.Our Study has shown that set of central buckle has a series of advantages: It can make the cable,beam and tower work together and reduce the bridge tower bottom shear and bending moment and the longitudinal displacement of the main beam.Moreover,the anti-buckling energy dissipation can be applied to the large span suspension Bridges of high-intensity seismic zones due to its better energy dissipation.(4)We also study the seismic response of suspension Bridges with different design parameters.After the viscous dampers are set in the tower-beam joints,the seismic analysis of suspension Bridges under uniform input is carried out.The results show that the viscous damper can effectively control the relative displacement of the tower beam.However,the change of damper parameters has an effect on the force of the tower: The bending moment and shear force of the bridge tower decrease with the increase of the damping coefficient C,and increase with the speed index.(5)In the end,we also study the seismic response of suspension Bridges in different bridge towers.The seismic response of concrete bridge tower,steel bridge tower and steel-concrete bridge tower suspension bridge is comparative analyzed.Due to the overall stiffness and the corresponding structure frequency of steel bridge tower suspension bridge are the smallest,at the same time,its shear force and bending moment of the tower are obviously smaller than others,so,its damping effect of the structure is the best.Therefore,the steel bridge tower suspension bridge is the best for the structure.