| The seismic wave is mainly composed of body wave and surface wave.Rayleigh wave is a kind of surface wave.Compared with other types of seismic waves,Rayleigh wave accounts for the highest proportion of ground motion energy,and the influence of different types of seismic waves on the ground motion of the valley is also different.In view of this,this thesis takes a long-span concrete-filled steel tube arch bridge across the V-shaped valley as the research object,and establishes a valleyarch bridge system model.The influence of Rayleigh wave incidence on the ground motion law of valley and the seismic response of arch bridge structure,and the influence of valley depth on the ground motion law of valley and the seismic response of long-span arch bridge structure are studied.This thesis mainly carried out the following work :(1)The effects of Rayleigh waves on the ground motion of a two-dimensional Vshaped valley site model with a valley depth of 250 m are studied by inputting P-SV waves and Rayleigh waves.The results show that the PGA(Peak Ground Acceleration)of Rayleigh wave on one side of the valley is larger,while the PGA on the other side is smaller.The PGA at the top of the incident side and the top of the outgoing side when the Rayleigh wave is input is 1.70 times and 0.40 times that of the P-SV wave,respectively,showing a strong non-uniform characteristic.(2)P-SV wave and Rayleigh wave are input into the free field model and the two-dimensional V-shaped valley site model with valley depth of 50 m,150 m and 250 m respectively to study the influence of valley depth on the ground motion of valley site.The results show that when the P-SV wave is incident,the horizontal PGA of the valley terrain area is smaller with the deepening of the valley depth.Taking the incident condition of seismic wave RSN1484 as an example,the horizontal PGA at the bottom of the valley with depths of 50 m,150 m and 250 m is 0.52,0.67 and 0.58 times that of the free field PGA,respectively.Under the incidence of Rayleigh waves,the non-uniform characteristics of both sides of the valley become more significant with the deepening of the valley depth.When RSN1484 is incident,the PGA amplitude ratios on both sides of the valley with depths of 50 m,150 m and 250 m are 1.14,1.84 and 3.26,respectively.(3)The P-SV wave and Rayleigh wave are input to the model of the river valley arch bridge system with a depth of 250 m,and the seismic influence of Rayleigh wave on the structure of the river valley arch bridge is studied.The results show that compared with P-SV wave,Rayleigh wave has obvious amplification effect on the internal force response of the main arch ring of arch bridge.The extreme values of axial force,bending moment and shear force of the main arch ring are enlarged by 1.81 times,1.62 times and 1.38 times respectively.This amplification phenomenon is mainly caused by the high-order vibration mode induced by Rayleigh wave.At the same time,the location of the extreme value of the axial force response of the arch ring under the action of Rayleigh wave and P-SV wave and the change rule of the peak value along the arch axis are obviously different.The axial force response of arch foot and vault is larger when Rayleigh wave is incident.When the P-SV wave is incident,the arch foot is larger but the vault is smaller.Taking the input condition of RSN1484 as an example,the ratio of axial force at the arch foot and the vault is 1.89 and 1.60 respectively.(4)The P-SV wave and Rayleigh wave are input into the free field model and the valley arch bridge system model with the valley depth of 50 m,150 m and 250 m respectively,and the seismic influence of the valley depth on the arch bridge structure across the valley is studied.The results show that the valley depth does not change the location of the extreme value of the axial force and bending moment response of the arch ring and the change law of the peak along the arch axis.With the deepening of the valley depth,there is an amplification effect on the internal force response of the arch ring,and this amplification effect is more significant when Rayleigh wave is incident.When RSN3495 is incident,compared with the free field response,the axial force and bending moment response of the upper chord of the arch ring under P-SV wave are amplified by 1.25 times and 1.20 times respectively in the 250 m deep valley,and the axial force and bending moment response of the upper chord of the arch ring under Rayleigh wave are amplified by 1.56 times and 1.52 times respectively. |
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