Thick Raft Foundation Interaction And The Punching Shear Capacity

With the development of the economy, the high-rise buildings and extre high-rise buildings come out. In order to make use of the underground space well, thick raft foundation is adopted more.Superstructure, raft and soil is an integrated structural system. Superstructure' s calculation is simple and muture. Interaction of raft and base is important. An approximately method is deduced and the free rectangular middle-thick plates on two-parameter foundation is analyzed. A program is developed to solve the bending plate. The computing results are well agreed with Winkler's elastic base. At the same time, the comparing this paper's solution with other's the method solution, it is proved that this approximately method is feasible.The punching shear strength of raft-column connections is a key to the raft's design. The author used finite element analysis calculated the stress of raft-column connections under vertical shear by ADINA program. Nonlinear material properties, connection of concrete and steel, the thickness of raft and different base are taken into account. Mechanism is analyzed by the results of effective stress and shear stress. Some results of finite element analysis are closed to those of the tests. If the base is too thin, it will break before raft-column connections; with the increasement of raft's thichness, capacity is increased; capacity is varied by different base model. How to select base model is important.At last, combined with the finite element analysis, theoretical studies and correlated references ,the paper put forward the design suggestions to raft-column connections.