Soil-structure Interaction Analysis Based On The Combining BEM And FEM

Based on combining BEM and FEM, the groundsill is molded, and the soil-frame structure dynamics interaction is studied. The main contents are summarized as follows: First, a groundsill model is proposed here by combining the BEM and FEM. In this model, the complexity of near field soil can be considered by using finite elementand the hemi-infinity of far field can be taken into account by using boundary element to simulate far field. Based on this, the soil-structure dynamic interaction equation is set up. The boundary element procedure and the finite element procedure are programmed. The numerical calculation demand is increased because of the overmuch soil elements. To simplify the analysis, the boundary element and finite element procedure, using the DOF reduction method what is the idea of statically equivalent of substructure, was programmed. Then, the static stiffness of the groundsill is got by the procedure and compared with the results obtained from the approximate method that described in the 2nd chapter. Because of the adoption of FEM, the proposed method to calculate the static stiffness of groundsill is suited and accurate more than the approximate method. After getting the relatively accurate static stiffness of groundsill, the soil-frame structure dynamics interaction is studied by the simplified method in the 4th chapter. Second, under the earthquake action, the structure will come into the elastic-plastic phase. Adopting the beam element model and Wilson- 9 integration algorithm, the frame structural time history response procedure is programmed. Third, many frames examples are analyzed. The effects of different site and seismic wave on the structural seismic response are discussed. Due to the soil-structure dynamic interaction, the dynamic characteristic of structure is changed, and the cycle is mount up. The value of this mounting up gradually reduces with the increase of cut wave velocity. Furthermore, on account of the soil-structure dynamic interaction, the structure response, not as the case when the groundsill is assumed to be rigid, contains slip and rock. When the soil is soft, the structural rigid motions affect the displacement remarkably. Especially, for the tall building, the P-effect is larger than that when the soil is assumed to be rigid. Under the action of various seismic waves, the rules of structural response are not same with the variation site. In the example analysis, the attribute of site affects little on elastic analysis but big on elastic-plastic analysis. The displacement of structure in non-linear analysis islarger than that in elastic analysis, and this trend increases with the softer soil. At the same time, the cycle of whole system increases, too.