Seismic Response Analysis Of Deep-water Rectangular Hollow Pier

In recent years, along with the rapid progress of traffic construction, deep-waterbridge which is of generally large span and deep water level is introduced in large res-ervoirs in southwestern China. Meanwhile, hollow piers which are lighter and able toreduce the bearing capacity of foundation are significantly applied in deep-water bridgeconstruction. Moreover, due to the complicated geological environmental conditionsand frequent earthquakes caused by potentially active fault zone, affected by seismicwaves, In the5.12wenchuan earthquake, caused the zipingpu bridge across10T beamfalling and5main pier is broken, researches on the rules of dynamic response fromdeep-water rectangular hollow pier is of great realistic meaning.In this paper, referring to finite element calculation method of fluid-structure in-teraction the5#Pier of Zipingpu Bridge as the basic mode, with three factors of waterlevel, water area (internal and external) and diaphragms taken into account, an analysison the self-vibration characteristics and dynamic response of deep-water rectangularhollow pier when affected by earthquake is made with results indicating that:(1) Water area has reduced the natural vibration frequency of pier, which becomesmore significant along with the increase of reservoir water level. Internal water plays amore significant role in reducing low-order modal frequency while external water ismore effective on high-order modal frequency; in water, diaphragm may reduce thenatural vibration frequency of pier significantly;(2) Spectrum characteristics analysis and baseline adjustment have been done onWenchuan seismic wave, after which, Wenchuan seismic wave’s fourier spectrum fallsin the lower range of0.5Hz~5Hz in vibration frequency, close to the natural vibrationfrequency of deep-water rectangular hollow pier when it trends to low-frequency stage;(3) Water level has greatly increased the dynamic response of rectangular hollowpier and both internal and external waters impose the similar influence on pier top dis-placement and acceleration, but external water has a large influence on the dynamicresponse of internal force and stress in pier, They were13.2%and19.7%respectively.Inwater, diaphragm affects the pier top displacement and acceleration insignificantly, Iton the pier internal force and stress increase by27%and18%,but internal force andstress obviously. Meanwhile, internal force and stress mutation take place at where adiaphragm is set up, making stress concentration easier, It will lead to the dynamic re-sponse amplitude increase;(4) Water level has a significant influence on the dynamic response of hollow pier, internal and external waters dramatically change the natural shape of vibration and theinternal force of pier while a diaphragm increases the stress concentration in hollowpiers. The three factors affect each other so as to increase the dynamic response of deep-water rectangular hollow piers;5Rectangular hollow structure of bridge pier and outland water caused by thenatural vibration characteristics and dynamic characteristics of bridge pier has a greatinfluence, Therefore when calculating the deep rectangular hollow pier’s vibration char-acteristics, so in deep water when calculating the vibration characteristics of rectangularhollow piers, should not simply use the simplified method to calculate the added mass,It makes small calculation results,It should be fully considered due to their structuralhollow pier pier dynamic characteristics change.