Dynamic Properties Of The Foundation Of Three Platforms

As an indivisible part of Chinese civilization,ancient architecture embodies the wisdom of ancient craftsmen and carries the spiritual and material culture of human beings.At present,more and more attention has been paid to the protection of ancient buildings.In view of the impact of environmental vibration on ancient buildings,many scholars have put forward a series of reinforcement and protection measures.However,most of the existing researches only focus on the superstructure,and seldom involve the influence of the structure of foundation on the dynamic characteristics of the superstructure.Survey data have found that the foundation of the three platforms in the Forbidden City are composed of bricks,clay and pebble,and have obvious periodic characteristics.Unfortunately,the influence of the periodic characteristics of the foundation of the three platforms on the dynamic characteristics of the superstructure has received little attention in the existing studies.Therefore,based on the existing data,the relevant geometric and material parameters of the three bases are obtained.Then,based on the basic theory of periodic structure,the dispersion relation of the three bases is solved,and the attenuation domain is obtained.Therefore,the influence of parameters such as initial pressure stress on attenuation domain is studied,and the optimal design of the foundation is carried out.Finally,the frequency domain and time domain response analysis of the foundation of the three platforms is completed,and some meaningful conclusions and suggestions are given.The research contents of this paper mainly include:1.The research status of the periodic structure and the foundation of ancient buildings are briefly introduced.The calculation method of attenuation domain is summarized and the finite element method is introduced in detail.2.The geological conditions of the foundations are analyzed and a reasonable typical element model is proposed.The material parameters of the foundation are obtained by using the composite material theory.Combined with empirical formula and measured data,the actual initial stress of the foundation is determined.Through geological survey data,the depth of the foundation is determined.3.The numerical analysis model of typical element is established by using finite element software COMSOL and the correctness of the model is verified.Based on the model,the dispersion relation of the foundation is calculated,and the attenuation domain is obtained.The influence of parameters such as initial stress value on attenuation domain is discussed and an isolation vibration reduction foundation with low frequency attenuation domain is proposed.4.The finite element software COMSOL is used to analyze the traditional foundation and the new foundation separately in frequency and time domain.On this basis,the dynamic response analysis of the superstructure with different foundations is completed,and the influence of different foundations on the dynamic response of the superstructure is revealed.The results show that the new foundation has better dynamic characteristics than the traditional foundation.The research work in this paper provides a new method for foundation design.