Comparative Research Of The Different Pile－tall Building Structures System In Dynamic Interactions

High-rise building with characteristics of high, heavy, large, deep basic calls for the base to assume a huge load of superstructure and overturning moment caused by the earthquake in order to ensure sufficient stability of the building. As a more advanced form of pile,branch pile has become a new hotspot of engineering field. In practical engineering, the branch pile has been more widely used because of its high bearing, pullout resistance and better economic returns. But comparing to sthaight pile,what action does the branch pile has and what problem we should pay attention to when it used as the base of high - rise building? So the comparison of different pile-high rise building structure's interaction is quite necessary.To study the dynamic characteristics of different piles under the earthquake and the law of the pile - soil - structure interaction system, the research group made a shaking table test called "research of pile - soil - structure of interaction"in the laboratory of Tongji University in January 2009. In addition, using the finite element software MARC, structure of both the process of the dynamic interaction of two system has been simulated under the same conditions.Shaking table test results can be used to verify the accuracy of numerical simulation.By comparing the digital simulation results of two kinds of structure system (including the maximum deformation, top acceleration composition, floor shear force and overturning moment, the local stress picture, etc), we got the following conclusions:Under the level earthquake waves, it has a clear separation between the cap and soil in the sthaight pile system and the pile has a greater degree of uplift to make a serious tilt and the movement upward. In the branch pile system, although the upper structure also has a tilt, the range is much smaller. And the cap and the soil contact well. The branch effectively prevents the deformation of the structural system. Branch pile system has a larger floor shear and overturning moment than the straight pile system,and with the input stimulus increasing, the rule remains. Stress picture also shows that at each floor, branch pile system's shear stress is greater than the straight pile system; the stress at the top of branch pile is evident less than the straight pile and there is also the stress concentrating on the branch that ensuring the structural stability. The branch piles at the corners played a more important role.The results show that the branch pile can reduce the deformation of the upper structure, but may cause local stress concentration in the superstructure. The results provide an effective foundation for the pile and tall buildings design to prevent and relieve the earthquake.