Research On Interaction Between Superstructure Under Differential Load-foundation-soil

Highrise building system consists of superstructure, foundation and soil, which are interacted and affected each other in loading action. But the traditional designing method adopted in engineering field regards the superstructure, foundation and soil respectively and calculates them separately. Disregarding the interaction between them, this segregation could make the internal forces of the superstructure not conform to the reality, and the result of the designing method becomes either unsafe or wasted, and leads to economic loss. Hence, the reasonable and practical designing method of structure and foundation relies on the over-all understanding of the interaction. At present, although a few of qualitative conclusions have been drawn from study on interaction, so many questions should be discussed and studied because of the complex of interaction theory.To settle the mainly problems occur in foundation and soil design, based on the research method of the interaction between superstructure under differential load — foundation - soil, the finite element analysis of the interaction under the conditions of consent rigidity and variation rigidity is taken. The problems of the model establishment of the interaction system are settled properly, and the complete results of the system stress and displacement are obtained. The characteristic of the system force and distort under the condition of different pile-foundation rigidity is revealed. For the special load system of the superstructure under the differential load, the proper variation rigidity design of the raft foundation which could reduce the internal secondary forces of structure, prevent the damage of the raft-foundation, and reduce the differential settlement of the foundation couldn't be ignored. Meanwhile the distribution regularity of load on the heads of piles and soil pressure under raft is achieved, the method named Sparse Outside Dense Inside that can achieve the balance settlement optimum design is given. The factors that affect the ability of carrying load of the soil among piles and thesettlement are analyzed. The paper indicates that to exploit the potential load-carrying ability of soil under the foundation could improve the system behavior under the load, reduce the cost of pile-foundation and the thickness of the raft, and almost differential settlement is eliminated.