Seismic Performance Analysis Of Long-span Stiff-skeleton Arch Bridge

Over the past two decades,Stiff-Skeleton Arch Bridge has gained popularity in our country because of its advantages in superior structural quality such as its light weight,excellent spanning capacity,convenient construction along with good seismic performances.The structure stress of the bridge becomes complex along with the increase in the span of the bridge,thus the influence of an earthquake on the bridge is intensified.Furthermore,our country China is an earthquake-prone country,and there is no special seismic code for large-span bridges here.Despite rapid development in methods bridge construction,the research on the seismic performance of long-span stiff-framed arch bridges is still in its infancy.Therefore,it has realistic significance and practical values to study the seismic performance of long-span Stiff-Skeleton Arch Bridge.Based on a long-span Stiff-Skeleton Arch Bridge,the spatial finite element dynamic model was established by using the finite element software Midas/Civil.The main contents of which are as follows:(1)The dynamic characteristics of the bridge are analyzed by using the multiple Rize vector method,and the self-vibration frequency and vibration pattern of the bridge is given.Then,the influence of the superstructure and both sides of the bridge approach on the dynamic characteristics of Stiff-Skeleton Arch Bridge were studied by comparing the self-vibration frequency and vibration pattern of the arch,the main bridge and the bridge.The performed analysis suggested that the bridge model should be adopted to analyze the dynamic characteristics of the Stiff-Skeleton Arch Bridge,for the superstructure and both sides of the bridge approach has a great influence on the dynamic characteristics.(2)The response spectrum analysis of the Stiff-Skeleton Arch Bridge is carried out.According to the acceleration response spectrum curve,the analysis has founded that the internal forces and displacements variation of the key sections including:arch foot,1/8span,1/4span,3/8span,and 1/2span of the bridgeas,by using CQC to combine three-direction earthquake load.The main conclusions are as follows:The most severe seismic response of the internal force appears on the arch foot section and 1/2 span section,which is the control section of the internal force of seismic design.The axial force is the control internal force of seismic design for it has the most severe seismic response of all internal forces.The lateral displacement is mainly contributed by the lateral seismic input,independent of the longitudinal and vertical seismic input.The maximal displacement of the section appears inconsistent,mainly concentrated between the 1/4span and 1/2span section.(3)Three records waves were selected to analyze the seismic response of the bridge under uniform seismic excitation.Then,the effects of different seismic waves on the internal forces and displacements are studied.To study the difference between the results obtained by the two analytical methods,the results of time history analysis are compared with the results of the response spectrum.In addition,the paper will study the longitudinal,longitudinal and vertical seismic input mode on the impact of time-history results.The main conclusions are:the response under the excitation of three seismic waves show good agreement,which indicates that the three seismic waves are close to each other.Different seismic wave has great influence on the results of internal force and displacement.The results of response spectrum method cannot meet the requirement of the structure safety,and it is only the response spectrum method and time-history method when combined could obtain more reliable results when the seismic performance of the long-span Stiff-Skeleton Arch Bridge is analyzed.The influence of seismic input mode on the results is great,and the vertical seismic excitation should not be ignored when analysing the seismic of long-span Stiff-Skeleton Arch Bridge.