Abstract:
Simplifying the 3D model into a 2D model for analysis is a method to improve the computational efficiency, but there is a certain deviation from the actual situation, especially in the complex terrain conditions, ignoring the out-of-plane terrain features may have a great impact on the 2D analysis results.This paper aims to discuss the difference of ground motion analysis between 2D model and 3D model. A 2D cross-section model and a 3D regional model are established based on the terrain of Moxi Platform, and the seismic response of the terrain in this region is analyzed. The surface GMAF distribution and acceleration spectrum curves of 2D model and 3D model are compared to obtain the difference between them. The variation law of ground motion under different incidence orientations of seismic waves is discussed. The results show that: for the 3D model, the seismic wave will be reflected by the surface of the complex terrain for many times, and the incident wave will cause a more obvious vibration phenomenon in outward direction, but the 2D model is easy to ignore this phenomenon. The seismic wave incident from different directions will change the values of in plane slope and out-of-plane slope of the ground surface, which will affect the reflection and scattering law of the seismic wave, and lead to the change of the vibration amplitude of each point. If this factor is ignored, it may be difficult to accurately assess the complex ground motions.