The Study On Transient Response And Natural Vibration Characteristics Of Damped Planar Structure

Pile foundations are playing an increasingly important role in the field of civil engineering. The most typical and common forms are the pile embedded wholly in soil, the pile embedded partially in soil, the frame structure embedded wholly in soil and the frame structure embedded partially in soil. Currently, the transient response research is relatively little and the natural frequencies and modes of pile foundations mainly adopt the finite element method to solve. But the finite element method is just an approximate solution, and the results are different with the different cell types, cell sizes and solving methods. Therefore, the research of transient response, natural frequencies, modes and critical damping has an important guiding significance in quality test of pile foundation and earthquake-resistant, anti-vibration designs.This paper sets up the basic equations of axial and flexural wave transmission above ground and below ground, introduces the basic principle of transient response, natural frequencies and modes, studies the natural frequencies, modes and critical damping of the one-dimensional single pile embedded wholly in soil in detail, and discusses the influence factors of natural frequencies, modes and critical damping. The study shows that the soil damping and soil hardness have a great influence on the natural frequencies of the one-dimensional single pile embedded wholly in soil, and the pile bottom soil hardness have a great influence on the modes of one-dimensional single pile embedded wholly in soil.Based on the method of reverberation-ray matrix, this paper studies the natural frequencies and modes of the two-dimensional pile embedded wholly and partially in soil, analyzes the factors, soil damping, soil hardness and other factors, how to influence the natural frequencies and modes, introduces the method for solving the critical damping of the two-dimensional pile embedded wholly and partially in soil. It is concluded that the soil damping and soil hardness have a great influence on the natural frequencies of the two-dimensional pile embedded wholly and partially in soil, and the soil hardness have some influence on the modes of the two-dimensional pile embedded partially in soil.The method of reverberation-ray matrix is applied to the frame structure, this paper studies the natural frequencies and modes of the frame structure embedded wholly in soil and the transient response, natural frequencies and modes of the frame structure embedded partially in soil. And it also discusses the factors, soil damping, soil hardness and other factors, how to influence the transient response, natural frequencies and modes in detail. The study shows that the soil damping and soil hardness don't affect the modes of frame structure embedded wholly in soil, however, they have a great influence on the modes of frame structure embedded partially in soil.This paper further studies the natural frequencies and modes of the single pile with different cross sections embedded wholly in soil and the frame structure with different cross sections embedded partially in soil, analyzes the natural frequencies and modes of the single pile embedded wholly in the two layers of soil and the frame structure embedded partially in the two layers of soil, and compares with the finite element method(SAP2000). It is found that the attenuation coefficient of different section is different in the same soil layer, and the attenuation coefficient of the same section is different in different soil layers.Finally, main conclusions are draw and some suggestions for further research are proposed.