Multi-tower High-rise Structure With A Large Podium Raft-soil Interaction Analysis And Construction Process Monitoring

Multi-tower high rise buildings with a large podium which can make full use of underground space as a parking area, which also combine the commercial purpose and the residential purpose are built more and more.No permanent settlement joints are set for the usage of the underground parking, the way to release the differential settlement and to make sure the connection between the tower and podium is to set the post-cast strips.At the same time, the post-cast strip involve second time pouring concrete, the pouring quality is not easy to make sure,it also increases the construction procedures, the dewatering works, the cost of the construction, and the wast of the underground water. More and more requirements of setting no post-cast strips are proposed by the construction company, which becomes a technical problem needed to be solved.This require the possibility of the foundation settlement coordination between tower and podium and evaluating the effect between different towers.In the design procedure, the towers and the podiums are calculated separately,which means the design method have not considered the effect of different towers podium foundation and soil interactions.These problems involve the accuracy of calculating the foundation settlement in soil mechanics and evaluating the ability of superstructure dealing with differential settlement.All above can be summarized in the design theory problems of controlling the foundation settlement.In this paper, three dimensions finite element model is built by ANSYS program, which take the interactions between superstructure foundation and soil into account.The calculation considered the effect with superstructure stiffness and without superstructure stiffness,the effects of different parameters in the model on the foundation stress and displacement are also taken into account.The main conclusions1. The interaction influence is obvious at edge components of the first and second floor, the deformation of the tower base tend to be rigid base deformation,the reaction pression of the soil tend to be placid.2. The interaction between tower and podium result calculated by finite element method show that the local bend of the tower raft foundation is major, the curvature value is positive and small for the vertical stiffness of the tower is big. The curvature value of the podium raft foundation is negative,and the integral bend is major, because of the tower influence, the top curvature value is-0.2‰which appears at the middle of the podium raft foundation.The influence of the negative curvature value in podium raft foundation should be taken into account in design procedure.3. The result calculated from different elastic modulus show that the less compressibility of the soil is, the less differential deformation and curvature value will be. Which show that the integral connection raft foundation between the tower and podium could perform better from lower compressibility and instantaneous settlement soil groundwork.4. The test data show that the value of the steel stress detectors which were set in the tower and podium connection part is small on the whole. This show that the cracking possibility is low.These detectors value grow flatly after the structure floors were built at the second floor, therefor the post-cast strips can be closed after the second structure floor is constructed in the condition of better connection between newly and early poured concrete.