Study On Site Reaction Method Under Non-Perpendicular Incident Wave

In the previous field reaction study, the seismic waves from the bedrock are generally assumed to be vertically propagating body waves, and then the seismic response research work is carried out according to this assumption. However, with the development of new technologies and new methods, the research of site reaction is deepening, and it is found that when the source is relatively close to the field, the seismic wave is not propagated vertically,but is propagated upwards at an angle. Therefore, it is more realistic to carry out the study of site response under non-perpendicular incident seismic waves.In order to find a theoretical calculation method of site response under the action of non -vertical incident seismic wave, the earth surface is covered with soil layer as the object of study,and the soil layer is regarded as horizontal infinite viscoelastic medium. According to the seismological principle, Based on the propagation characteristics of the seismic wave, the characteristics of the propagation path of the non-perpendicular incident seismic wave to the same observation point are deduced, and the seismic wave is calculated according to the propagation characteristics of the seismic wave and the incident wave. Finally, the relationship between the damping ratio and the ground motion is obtained by studying the energy attenuation characteristics of the seismic wave during the propagation process by referring to the shear layer method in the dynamic response analysis of the soil. Based on the above results,the superposition principle is used to calculate the ground motion time. The calculation results show that the proposed method has the advantages of high computational efficiency, high precision and good reliability, which can overcome the shortcomings of conventional numerical calculation results and poor stability, and obtain the following understanding:(1) The traditional method of analyzing the site response is often only the case when the seismic wave is incident vertically. According to the principle of seismology and the propagation characteristics of seismic waves, a new method is proposed, which can be used to study the effect of non-vertical incident seismic wave Under the site reaction.(2) The feasibility of the method is verified by the theoretical model and the engineering example, and it is used to calculate the site response analysis when the body wave is calculated,and the method can be applied to the reaction analysis of the multi-storey site.(3) The advantage of this method is that it is not limited by the thickness of the soil layer,and the adaptability is strong. In order to overcome the shortcomings of the conventional numerical calculation results, it is necessary to avoid the calculation of all the wavefields without numerical processing, unconditionally stable , The accuracy of the calculation is not controlled by the shape and size of the network. When the seismic wave is large, it still has good calculation precision, the operation is simple and convenient, the reliability is good, the calculation precision is high and it is easy to be applied to the project.(4) This paper focuses on the influence of the incident angle on the site response, the incidence angle of the ground motion is different, and the displacement time is different. When the incident angle changes, the variation of the peak value of the displacement of the different types of incident waves is different. The incident angle is different, which causes the ground motion energy to be redistributed. With the increase of the incident angle, the fluctuation intensity decreases and the fluctuation duration is shortened, The arrival time of the interface is increased, the distance of the propagation path in the layer increases, and the propagation time is prolonged, which leads to the arrival point of the calculation point. The first wave of time delay phenomenon. In addition, the damping ratio is different, the resulting ground motion intensity is also different, the greater the damping ratio, the more serious displacement attenuation.(5) When the real seismic wave is input, the spectral acceleration of the different seismic waves is different, which causes the peak acceleration of the calculation point to be different. It is pointed out that in the general engineering seismic design, the incident seismic wave is simplified as a vertical upward In practice, it is necessary to study the effects of seismic wave oblique incidence.