Shaking Table Test Of Pile And Composite Foundations’ Dynamic Behavior In Layere D Soils Subjected To Earthquake Excitation

China is earthquake-prone countries. Frequently occurred earthquake hazards caused huge casualties and property losses. Seismic performance of foundation is one of the key factors in seismic design of buildings and thus raise us a crucial topic on studying the seismic performance of foundations; since however strong and safe the super-part is, the structure could also be damaged or destroyed provided that the sub-part, namely the foundation, fails. Shaking table test is a important method to study the seismic performance of buildings. According to the shaking table test of pile and composite foundations in layered soils, this paper investigates the dynamic characteristics and the respond law of structure and soil, also compares and analyzes the result of numerical simulation and experimental, gained some valuable reference for the actual project resultsThis work mainly consists of three parts shown as follows:1. A large laminar shear soil container was developed. The shaking table test of pile and composite foundations in the layered soil was carried out within this container. In order to better imitate field testing, layered soils were used:sand, soft clay, and sand for the upper, middle and bottom layers, respectively. Two different types of foundations were considered including the pile and the composite foundations. The Shape Acceleration Array (SAA) was used for data collection.2. Based on the large amount of data obtained by the shaking table test, this paper analyzes the acceleration responses, displacement responses and strain responses respectively of the pile foundation, the composite foundation, the superstructure and the soil, under horizontal seismic excitation. The response mechanism of foundation-soil-structure interaction was also studied.3. The commercial finite element method (FEM) software ABAQUS6.10was used for numerical simulation. A3D model was developed and the nonlinear dynamic interaction between the foundation, the soil and the superstructure was analyzed. The effectiveness and the rationality of numerical simulation was finally validated via the comparison with the experimental results.Through the model test and numerical analysis, draw some reference value and practical significance of the conclusions:1. Experimental results show that the border effect of the soil container is small, can be an ideal way to eliminate boundary seismic reflection and scattering phenomena, a better simulation of soil shear movement.2. Acceleration dynamic factor magnifies in the sands, decreases in the soft soil. In the soft clay the peak of acceleration and the power factor was significant. 3. As the input peak ground shaking increases, the acceleration power factor of measuring points at different depths is reduced,namely, in the cumulative effect of the earthquake, soil nonlinearity is significant, the ability of the soil to pass seismic waves is weakened, acceleration dynamic coefficient of soil decreases.4. In the same conditions, the peak acceleration of soil is slightly larger than the pile of each point corresponds to the same measuring point; composite foundation pile is slightly larger than the peak acceleration of pile each point corresponding to each pile.5. Acceleration peak of measuring point at shaking table superstructure is greater than pile and composite foundation with superstructure at the measuring points; peak acceleration of pile measuring points at the top of the superstructure is greater than the peak acceleration of upper structure of composite foundation. With the increase of the peak ground shaking, the upper structure acceleration amplification factor decreases.6. The bending moment’s maximum amplitude of composite foundation and pile are at the interface of hard and soft soil, at the top of the pile, the moment of pile is much larger than the pile of composite foundation.7. The displacement reaction of composite foundation pile cap is greater than the pile cap of pile. On different conditions, displacement amplitude of composite foundation pile cap is approximately twice the displacement amplitude of pile.8.On the same condition, the pile displacement of composite foundation is greater than the pile displacement of pile. Under the small peak conditions (0.1g), the displacement of soil is greater than the displacement of pile, under the large peak conditions (0.2g,0.4g,0.8g), the situation is the opposite.