Research On Single Tower Cable-stayed Bridge's Seismic Response Crossing Faults

Near-fault ground motions are often accompanied by surface rupture,velocity pulse and permanent ground displacement,which are significantly different from general ground motions and far-field ground motions.With the construction of the Sichuan-Tibet Railway and the vigorous investment in the construction of highways and railway bridges in areas with high seismic intensity in southwest China,the total number of bridges will increase significantly.Due to the influence of objective conditions such as topography,route planning,and engineering cost,many bridges will have to be built near active faults or even directly across faults.In addition,because some active faults at the site of existing bridges have not yet been discovered at the beginning of the design,the bridges are currently facing potential near-fault damage risks.Multiple strong earthquakes at home and abroad also show that the surface rupture is uncertain,and the bridge structure far away from the fault cannot completely avoid the risk of near-fault earthquake damage.In order to research the impact of this special type of ground motion,the main contents of this paper are as follows:(1)For three common types of faults,the causes of ground motion characteristics such as directional effects,slippage effects,wall effects and vertical effects are analyzed from the perspective of fault rupture mechanism;based on the PEER ground motion database,a large number of actual earthquakes are selected to research the four effect characteristics.The correlation between structural seismic response,pulse period and ground motion parameters and strength index,and the characteristics of pulse response and non-pulse earthquake and seismic response spectra of different pulse periods were analyzed.(2)The single-tower cable-stayed bridge structure is used to cross the fault,the main beam and the tower are simulated separately,and a simplified mechanical model is established;the single-tower cable-stayed bridge model of the floating system is established based on ANSYS finite element software.In dynamic time history analysis method,according to the type of fault and different research purposes,a variety of ground motion input methods were respectively adopt,and seismic waves with different nearfault ground motion characteristics was input for calculation and analysis.Effects of traveling wave effect,velocity pulse,pulse period,pulse number and fault crossing angle on the seismic response of the structure were researched.(3)According to the above research results,the single-tower cable-stayed bridge with floating system crossing faults has been designed for shock absorption.The longitudinal viscous dampers and transverse E-shaped steel dampers was adopt for antiseismic design scheme.The parameter sensitivity of the damper coefficients was analyzed.The dynamic characteristics and seismic response of the single-tower cable-stayed bridge before and after the seismic design were compared and analyzed.Reference for seismic design of bridge structures across faults was provided.