| Engineering structures such as bridges and tunnels that crossing the fault zone face a greater risk of damage under the effect of earthquakes.The pulse effect and the permanent displacement caused by fault rupture are the main causes of structural damage across the fault.The existing seismic codes lack the corresponding design theory,so it is very important to research the seismic response of fault-crossing bridges and take corresponding seismic fortification measures.Moreover,the seismic analysis of structures requires the selection of reasonable input ground motion,which is the basis for explaining the seismic damage mechanism of fault-crossing structures.However,there is currently a lack of actual fault ground motion records across both sides of the fault,and various specifications have not provided a reasonable simulation method for input ground motion for fault-crossing engineering.as input ground motions of fault-crossing bridges.Therefore,in order to solve the above problems,based on the existing methods,a hybrid simulation method for input ground motion of fault-crossing bridges is proposed using the theory of combining the physical model of faults and the equivalent pulse model,and seismic response analysis is performed.The main work is as follows:1.This paper summarizes several simulation methods of the ground motions in the fault region.the commonly used methods based on pulse function and fault physical mechanism are introduced in detail,and their characteristics and problems are analyzed.And the seismic response characteristics of beam bridges and cable-supported bridges fault-crossing under fault ground motion excitation simulated by the above method are summarized to provide reference for their earthquake protection.2.In order to solve the problem of input ground motion of bridges fault-crossing,this paper proposes a hybrid simulation method combining an equivalent pulse model and physical model of faults based on the existing methods,constructs a corresponding fault model based on the geological survey data of the bridge site and the method of determining the input parameters of the fault model,and generates high-frequency ground motions at the target points on both sides of the fault by an improved stochastic finite fault method.According to the characteristics of the ground motion of the strike-slip fault,the equivalent pulse model is used to simulate the low-frequency pulse characteristics of the fault normal and parallel ground motion respectively,and the spatial variability of the ground motion on both sides of the fault is realized by constructing a conversion matrix considering the spatial variability of the ground motion.The high-frequency and lowfrequency ground motions on both sides of the fault are superimposed at the cut-off frequency after high and low-pass filtering to obtain broad-frequency ground motions.Finally,the simulation results were compared with the GMPE ASK14 ground motion prediction model and near-fault ground motion records to prove the reasonableness of the simulation method.3.Based on an actual suspension bridge of fault-crossing,a 3D finite element model of the whole bridge is established based on OpenSEES.The simulation method proposed in this paper is used to generate the ground motion time interval at the bridge site as the input ground motion of the suspension bridge across the fault,and the dynamic time analysis is performed accordingly to obtain the seismic response characteristics of the bridge.The effects of fault span angle,permanent displacement amplitude and high and low frequency components of ground motion on the seismic response characteristics are analyzed to reveal the seismic response characteristics of the fault-crossing suspension bridge.In order to further prove the rationality and effectiveness of the simulation method,several existing simulation methods are compared with the simulation method proposed in this paper,and the effectiveness of the method is verified by the seismic response of the bridge. |
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