Seismic Performance Analysis Of Curved Box Girder Bridge With Small Radius Based On Pile Soil Structure Interaction

Curved bridges have emerged in large numbers in traffic networks due to their unique and beautiful lines and good adaptability.However,the irregularity of the curve bridge causes its internal force distribution under the action of earthquake to be more complex and the epicenter is more vulnerable.The bridges damaged by previous epicenters are frightening.Many experts and scholars have proposed many reasonable seismic design suggestions by investigating the principle and process of the destruction of the curve bridge,which has improved the seismic performance of the bridge structure to some extent.However,how to effectively alleviate or even avoid the bridge damage in the epicenter is still an urgent issue to be solved in the field of earthquake resistance.This paper uses a small radius curved box-girder bridge as the engineering background to carry out the response analysis under the action of earthquake.The details are as follows:(1)Analyze the dynamic characteristics of pile-soil structure under the change of radius of curvature of curved bridge.The results show that with the increase of radius of curvature,the fundamental frequency of structures is decreasing,regardless of the effect of pile and soil.The amplitude of change is not obvious.When the pile-soil interaction is not considered,the frequency change amplitude is as high as 17.91%,but only 7.45%when considering the situation;after considering the pile-soil interaction,the overall rigidity of the structure decreases,and the system becomes soft;The structure of curvature radius has the same frequency amplitude after considering the action of piles and soils.The fundamental frequency is the most affected,the increase is close to 60%,and the smaller the radius of curvature is,the larger the degree of influence is;the radius of curvature mainly affects the frequency and the effect of pile and soil.It has a great influence on the vibration mode of the structure.(2)Based on the response spectrum theory,the internal forces and displacements of the curve bridge considering the pile-soil interaction under the four excitation modes of the Shun-bridge,the cross-bridge,the bridge-to-vertical,and the cross-bridge to the vertical are analyzed.The results show that:Under the lateral-bridge excitation,the bending-torsional coupling of curved bridges results in a displacement response perpendicular to the direction of excitation;under lateral excitation,the lateral displacements of the main bridges and piers of curved bridges are larger than those of longitudinal ones;and the piers are more prone to lateral shear under horizontal bridge excitation.Cut damage.(3)Based on the response spectrum theory,the influences of curvature radius,direction of excitation,bearing restraint method,and eccentricity on curved box girder bridges were analyzed.It was found that the support methods for the combination of one-way movable bearings and pier girders for intermediate piers were better than single ones.The method of consolidating the movable support or the pier beam is reasonable;the reasonable eccentricity of this curve bridge is 0.15m.(4)Based on the nonlinear dynamic elasto-plastic theory,the time history analysis of the curved box-girder bridge subjected to rare earthquakes was conducted using the time-history curve of the San Fernando seismic acceleration corresponding to the site conditions and amplitude modulation to investigate the response status.The results show that:Under the rare earthquake of 7 degrees,the risk of falling beams of the curved bridge is small,the fixed pier is more vulnerable,and the plastic hinge appears at the top of the pier or the bottom of the pier.The damage of the pier considering the pile and soil is more serious.(5)Comparing the differences between the response spectrum method and the elasto-plastic method,the results obtained by the elasto-plastic method are larger than the response spectrum method.The error between the bridge-to-axis excitation and the bridge-to-excitation is as high as 55.05%and 28.34%,respectively.Elasto-plasticity method is used for calculation.