Analysis On Seismic Performance Of Long-span Bridges With High Piers In Deep Water Considering Pile-soil Interaction

With the continuous development and improvement of China's public transport infrastructure,the number of long-span bridges with high piers in deep water is increasing day by day.Although there have been many previous studies on the seismic performance of long-span bridges with high piers,most of them have ignored the influence of pile-soil interaction or hydrodynamic pressure.Furthermore,the research on the combined effect of the two is still not deep enough in particular,which leads that the current seismic resistance design specification of bridges lacks definite guidance and explanation on the simulation methods for hydrodynamic pressure and pile-soil interaction.Therefore,it is necessary to further conduct systematic research in this field.Taking a long-span continuous rigid-frame bridge with high piers in a deep reservoir area as engineering background,and considering the influence of pile-soil interaction and hydrodynamic pressure as well as combined effects of the two,this thesis aims to carry out qualitative and quantitative aseismic research respectively based on source code analysis platform OpenSEES.The main contents and conclusions of this study are as follows:(1)Based on OpenSEES software,the codes for a finite element model of nonlinear benchmark of the bridge are compiled concerning a typical long-span bridge with high piers of deep water in the highly seismic region.On the ground of finite element analysis model of nonlinear benchmark,six types of analytical models are established respectively:? Neither hydrodynamic pressure nor pile-soil interaction is considered;? only considering the hydrodynamic pressure;? the consideration of pile-soil interaction based on "m" method;? the consideration of pile-soil interaction based on "p-y curve" method;? "m" method +hydrodynamic pressure;?"p-y" curve method + hydrodynamic pressure.By inputting two sets of seismic waves' time-history excitations,the effects of hydrodynamic pressure and pile-soil interaction on the dynamic properties and seismic response of bridges are analyzed qualitatively.The study shows that considering the hydrodynamic pressure and the pile-soil interaction both reduces the vibration frequency of the bridge structures.However,the effects of hydrodynamic pressure and pile-soil interaction on the seismic response of bridge are not to promote or counteract,but are related to the characteristics of the input of seismic waves.(2)100 sets of random seismic waves are selected to consider the uncertainty of the earthquake,and the probability seismic demand model(PSDM)of different components of bridge is established respectively by using the peak ground velocity(PGV)as the intensive parameter of seismic ground motion.Then the corresponding seismic vulnerability curve is set up with the curvature of the pier top,the bottom of pier as well as the displacement of the support as the damage index respectively,and the seismic performance of bridge in deep water is quantitatively analyzed and evaluated.The results show that both pile-soil interaction and hydrodynamic pressure increase the failure probability of pier top along the direction of bridge;the effect of hydrodynamic pressure will increase the failure probability of seismic damage at the bottom of pier,but the effect of pile-soil interaction is just the opposite.