Theoretical Analysis And Experimental Research For Contact Stresses Between Large Size Flexibility Foundation Slab And Base

In the Foundation Design Code, there only has the provision of the bending moment calculation formula when the aspect ratio of the steps is less than or equal to 2.5, but when the aspect ratio is greater than 2.5, there have not calculation basis. Now, the flexible foundation design of transmission line are calculated by 2.5 control plate aspect ratio, however, this limitation makes the floor thickness is big, also increased is the material consumption of foundation slab. The key of the bending moment calculation method is to determine the contact stresses between foundation slab and base. In the traditional calculation method and design code of building foundation, the contact stresses was considered to be linear distribution. Actually, the contact stresses between foundation slab (especially large flexibility foundation slab) and soil tend to present nonlinear distribution, its distribution form is mainly composed of the type of foundation soil and the rigidity of the foundation slab. So it is a complex and practical work to analyze the distribution of contact stresses between foundation slab and base.On the basis of the experimental results, this paper constructed the distribution function of the nonlinear contact stresses on square foundation slab, analyzed the influence of bending moment calculation in the existing specification by the nonlinear contact stresses. Introducing symmetry conditions of foundation slab, meanwhile, this paper get the displacement function when symmetric loading based of the displace-ment function with complement remainder raised by Yanzongda. Through Fourier series expansion on the load applied to square foundation slab and the polynomial of displacement function, and according to bending equation and boundary conditions of the plate, we can get those undetermined coefficient of the displacement function when contact stresses is a nonlinear distribution. Then according to symmetrical load act on the square board, we can get the analytical solution of the displacement and internal force of foundation slab on elastic foundation with four edges free.In order to verify the accuracy of the nonlinear contact stresses distribution function, this paper simulated the interaction between foundation slab and base under the symmetrical load by using the finite element analysis software ANSYS, and compared the result with the distribution function. Meanwhile, this paper designed a series of different aspect ratio of the base plate model, and used pressure membrane systems and soil pressure box to determine the contact stresses distribution forms between foundation slab and base with different soil types, different aspect ratio, different loads, finally, this paper compared the results of the measured contact stresses to the analytical solutions and the finite element analysis.