Study On Interaction Of Pier And Water Under Earthquake Considering Fluid-Structure Interaction

In21stcentury, many large bridge projects have been in planning and construction,especially in cities along rivers more bridges will be built in order to form a round citycommunication. Moreover, earthquake happens frequently in China each year and the areawhose seismic intensity is above7degree should cover more than half of territory of our nation.In bridge seismic design field, further studies may be lacking on the problem of fluid-structure intereation (FSI for short). In lots of key projects, especially in long span bridgeconstruction, the effect of wave and fluid can not be dismissed. In this context, the study oninteraction of pier and water under earthquake is necessary.The work of this paper includes the following4aspects:(1) The paper summarized the development prospect of long-span bridge and the newrequest for deep water bridges in special environment and surveyed the development and statusof FSI problem. on basis of the above work, the problem in this field was pointed out.(2) This paper performed a comparative study on the calculation method of earthquakehydrodynamic pressure in seismic codes of bridge between China and Japan through acalculation example of a deep water pier, and analyzed the similarities and differences of bothmethods. The result showed that the calculated value of pressure according to Japanese codeswas three or four times more than that of Chinese codes.(3) Taking the Third Nanjing Yangtze River Bridge as a background, a pile-cap pier modelwas designed and built by using the similar principles with the scale factor of1:50. A shakingtable test of this pier model was carried out in two cases of model around water and around nowater. The differences of dynamic response, acceleration, stress,strain and hydrodynamicpressure in each case were obtained by analyzing the test data, and the characteristic of watereffect under earthquake was summarized. The natural vibration frequency of pier decreasedfrom9.16Hz to6.72Hz, and the phase difference was obvious between the water case and nowater case in sine wave load test and the largest rate of acceleration increase reached22.4%.And the rate for acceleration reached40.0%in earthquake wave and stress and strain increasedaccordingly. So the effect of earthquake hydrodynamic pressure was so evident thatmonographic study of the pressure is essential in aseismatic design of the bridges. (4) A numerical simulation of practical pile-cap pier of The Third Nanjing Yangtze RiverBridge around water was carried out under earthquake. And the dynamic response of this finiteelement model was analyzed. The simulation results matched well with the experimental resultsby comparing with the results of shaking table test.