Research on Seismic Input Method of Layered Ground Foundation

Zhonghui Bi,Binghui Cui,Yafei Zhai

doi:10.1109/access.2021.3070479

Abstract

The seismic input of layered foundation is an essential part of seismic analysis of structure- foundation system. Most of the traditional seismic input methods only consider the first reflection process of seismic waves at the interface of different media, ignoring the subsequent reflection and refraction propagation process, which can not truly reflect the wave propagation process in the layered foundation. This paper proposes a new seismic input method for layered foundation, considering all reflected and refracted waves. Firstly, the viscous-spring artificial boundary model of the layered foundation is established, which can simulate the absorption of scattered waves and the elastic recovery capacity of semi-infinite foundation at the same time. Then, based on the wave mechanics theory, the equivalent nodal force calculation formula is derived to realize the vibration input of layered ground. Finally, the calculation results of the layered foundation and two-way surge tower engineering are verified. The results show that: compared to the traditional input method, the method proposed in this paper has a significant influence on the seismic response of layered foundation, and the method in this paper can better meet the accuracy requirements of engineering earthquake resistance, which provides an effective and practical calculation method for seismic analysis of layered foundation structure.

Highlights

In the past few decades, there have been hundreds of severe earthquake disasters globally, which have caused significant losses to people’s lives and properties
A viscous-spring artificial boundary was applied to the two-layer horizontal finite foundation model’s truncated boundary to simulate the two-layer infinite foundation’s radiation damping effect, and equivalent nodal forces were applied on the truncated boundary, which verified the accuracy and effectiveness of the method
It is applied to the layered foundation-tower-water dynamic interaction

Summary

INTRODUCTION

In the past few decades, there have been hundreds of severe earthquake disasters globally, which have caused significant losses to people’s lives and properties. VOLUME 9, 2021 a viscous-spring artificial boundary model considering the direct reflection of the wave on the top of the layered foundation and applied it to the seismic analysis of gravity dams on the layered foundation. In this paper, based on the previous research results, a new seismic input method for the layered foundation is proposed, combining the viscous-spring artificial boundary theory and the wave propagation law in layered soil. The method considers the refraction and reflection characteristics of elastic waves in different layered media and simulates the radiation damping effect of infinite foundation on the seismic wave. It is necessary to intercept the finite near-field foundation from the natural foundation for calculation, and apply the artificial boundary model on the foundation’s truncated boundaries to simulate the radiation damping effect of infinite foundation on the seismic wave [27], [28]. When P-wave and S-wave are vertically incident into layer L from layer L − 1, the amplitude ratio of the reflected wave to incident wave in layer L − 1 is αrP(L−1)L and αrS(L−1)L , respectively, and the calculation formula is shown in (5) and (6); The amplitude ratio of refraction wave to incident wave in layer L is αtP(L−1)L and αtS(L−1)L , respectively, and the calculation formula is shown in (7) and (8); When P-wave and S-wave are vertically incident into the L − 1 layer from the L layer, the amplitude ratio of the reflected wave to the incident wave in the L − 1 layer is αrPL(L−1) and αrSL(L−1), and the calculation formula is shown in (9) and (10); The amplitude ratio of the refracted wave to the incident wave in the L − 1 layer is αtPL(L−1) and αtSL(L−1), and the calculation formula is shown in (11) and (12)

EQUIVALENT NODAL FORCE

ENGINEERING EXAMPLE

Findings

CONCLUSION