Seismic Response Analysis Of High-pier And Long-span Continuous Rigid Frame Bridge

With our country economic and construction rapid developing, large amounts of high-pier and long-span continuous rigid frame bridge have also been applied. Because of the excellent crossing ability of high-pier and long-span continuous rigid frame bridge, so it is favored by more and more mountain roads. At present, the seismic research of high-pier and large-span bridge structure is relatively weak in our country. Therefore, this paper has done some researches of the seismic response of high-pier and long-span continuous rigid frame bridge.The main research contents of this paper as follows:(1) Utilize the MIDAS/CIVIL to analyze the Xue Jia Ba 2# high-pier and long-span continuous rigid frame bridge’s dynamic properties of the structure, and analysis of the structural vibration regularity. On the basis of the results found that :①The first type of vibration mode is the whole structural vertical bending + longitudinal floating, there may be has plastic rotation at the bottom and top of the bridge pier, so enough attentions should be took to the bottom and top of the bridge pier,and strengthen design and reinforcement in the plastic hinge positions.②The second and third type of vibration mode are transverse bending.so, it may appear bigger transverse displacement because of the transverse stiffness is relatively low.③Higher vibration modes mainly influence the vertical seismic response of the bridge.(2) Utilize Response spectrum to analyze and research the high-pier and long-span continuous rigid frame bridge’s seismic response. By comparing the three directions’ seismic excitation contributions on the various structural internal forces and displacements in three conditions, determine the combination of seismic wave. On the basis of the analytic results found that: ① The combination of seismic wave should include longitudinal seismic excitation and transverse seismic excitation, and can ignore the vertical seismic excitation if the seismic fortification intensity is low. ② The pier’s intermediate diaphragms can heavily influence pier’s displacement, especially the longitudinal and transverse displacement. Therefore, by set the intermediate diaphragms in the reasonable positions, it can effectively reduce the displacement of pier when design the hollow pier.(3) Under the three seismic waves, analyze the structural seismic response to select the most compatible earthquake wave. By compare the results of structural seismic response of three seismic waves, it can found that although the peak acceleration of seismic wave is same, but the spectral characteristics of seismic wave can obviously effect the structural seismic response.(4) According to the analysis comparing results of the response spectrum and time history, select a satisfied code seismic wave.(5) Utilize analysis method of Dynamic time history to analyze the structural seismic respond when set up HDR bridge bearings on the top of side span piers. Under the effect of seismic force,we found that:①Bearing has little impact on longitudinal moment of beam, but can obviously decrease beam transverse shear;②Bearing has little impact on transverse shear of main piers, but it can obviously decrease the side span piers because that bearings are set on the top of side span pier, and it also proves that bearing can obviously reduce transverse shear;③Bearing can reduce longitudinal moment and shear at the bottom of main piers, but the longitudinal moment and shear of side span piers increase. This is conductive to overall structural force, and improve the seismic performance of the structure;④Bearing’s effect of displacement of beam and main piers can be ignored;⑤Under the seismic force, the maximal internal force of beam appear in the root of beam, and piers’ maximal internal force appear in the bottom and top of piers. Therefore, we need to pay particular attentions to the seismic design of these key positions.