Study On Dynamic Response Of Continuous Rigid Frame Bridge With High Piers Considering Terrain Effect And Oblique Incidence Of Seismic Waves

In recent years,the frequency of earthquakes has brought life and property threats,bridges as an important transport hub once the consequences will be disastrous.This paper studies the seismic response of high pier continuous rigid frame bridge under the consideration of terrain effect and oblique incidence,in order to provide reference and reference for the seismic design of this kind of bridge in the future,this paper mainly do the following research work and draw the relevant conclusions:Firstly,this paper introduces the method of seismic wave oblique input based on viscoelastic artificial boundary and establishes two-dimensional rectangular finite element model based on Abaqus viscoelastic artificial boundary for the calculation of P wave and SV wave oblique incidence.Based on the viscoelastic artificial boundary,seven two and three dimensional site models are established by Abaqus finite element software,which include flat land,concave valley and convex ridge.The seismic response characteristics of P wave and SV wave at different incident angles are studied by comparing the seismic response values of surface observation points.The results show that the seismic response time of each site should lag behind the vertical incidence,the larger the incident angle,the more obvious the lag phenomenon is,and the more obvious the effect of valley and ridge topography on the ground motion is,compared with the flat terrain,the seismic response time of each site should lag behind the vertical incidence.Earthquakes on the surface of valleys and ridgesThe response value increases with the increase of elevation,and the seismic response at the top of the slope is the largest,and the magnification effect of the earthquake is more obvious when the slope height(slope gradient)of the valley and ridge is larger.The horizontal seismic response values of the left surface observation point(near the side of the incident wave source)on the left side of the valley site are larger than the oblique incident wave of 15 and 30 on the right side of the P wave and SV wave.It shows that the valley topography has a certain shielding effect on the horizontal seismic wave propagation,and the calculated results of the seismic response value of the 3D model are slightly larger than that of the two-dimensional model.Taking a practical bridge as an example,the finite element model of three-dimensional continuous rigid frame bridge with high piers is established by Abaqus,and the acceleration time history of each observation point on the ground surface is applied to the bridge model as ground motion.The influence of concave valley site on the seismic response of bridge(longitudinal bridge)is analyzed with different waveforms and incident angles.The results show that the seismic response of bridge is obviously different when P wave and SV wave are incident vertically and oblique.The seismic response results of different piers are different under the same seismic waveform and incidence angle.In general,the seismic internal force response of the low pier near the top of the slope is obvious.The higher the high pier at the bottom of the slope,the larger the pier height,the greater the seismic response value of the horizontal direction(longitudinal bridge direction)when the source of the incident wave is closer to the incident wave source;The local slope gradient is changed for the valley site where the bridge is located,and compared with the original model,the results show that the change of local slope gradient in the valley terrain has little effect on the seismic response of the bridge.In order to study the influence of different parameters of pier on seismic performance of continuous rigid frame bridge with high pier under the seismic wave oblique incidence under topographic effect,the seismic behavior of continuous rigid frame bridge with high pier is studied.The linear elastic analysis of continuous rigid frame bridge model with high piers with different piers cross-section and tie beam setting parameters is carried out under the oblique incidence of P-wave.The results show that the solid pier can reduce the pier stress more effectively when the section area of the pier is the same.When the section size and longitudinal stiffness are the same,the hollow pier can effectively reduce the stress of the pier,and considering the dynamic factors,the more the stiffness of the piers is,the more the earthquake resistance is.