This paper deals with the modeling of the plane frame structure-foundation-soil system. The superstructure along with the foundation beam is idealized as beam bending elements. The soil medium near the foundation beam with stress concentrated is idealized by isoparametric finite elements, and infinite elements are used to represent the far field of the soil media. This paper presents the modeling of shear wall structure-foundation and soil system using the optimal membrane triangular, super and conventional finite elements. Particularly, an alternative formulation is presented for the optimal triangular elements aimed at reducing the programming effort and computational cost. The proposed model is applied to a plane framecombined footing-soil system. It is shown that the total settlement obtained from the nonlinear interactive analysis is about 1.3 to 1.4 times that of the non-interactive analysis. Furthermore, the proposed model was found to be efficient in simulating the shear wallfoundation-soil system, being able to yield results that are similar to those obtained by the conventional finite element method.

Structural integrity and seismic protection of the buildings against earthquake have been challenging among structural engineers. Many studies have been devoted to development of seismic isolators to improve the seismic behavior of civil structures. This study presents the analysis of building structures with SAP2000 considering soil structure interaction and base isolation effects under El Centro. Four different models are analyzed including fixed base structure, base isolated structure, frame supported by spring representing the soil and structure with combined base isolation and spring. The seismic results are investigated in terms of displacement, shear force, axial force, moment and drift of the columns and beams. It was observed that the soil structure interaction provides some flexibility to the structure by increasing the displacements of the structure and imposing internal forces variation to the system. Therefore, modeling base isolation together with consideration of soil structure interaction leads to better prediction of structural response.

In urban construction with the presence of tall buildings adjacent to short buildings, civil engineers have tried to connect low-rise rigid buildings to tall buildings in order to enhance the rigidity of the towers and decrease seismic response induced by earthquake excitation. From recent developments in earthquake energy dissipation systems, the application of viscous dampers for coupling of parallel and adjacent buildings to reduce earthquake effect has been considered by civil engineers, and many investigations have been conducted. In the present study an attempt has been made to evaluate the effect of connecting reinforced concrete towers to short rigid building through viscous damper devices. For this purpose, a 10-story RC tower connected to two short RC buildings by viscous damper was modeled and analyzed under Elcentro (1940) earthquake record excitation by using the finite element technique. In addition, the effect of various viscous damper damping coefficients on seismic response of the tower was evaluated by analyzing the aforementioned tower with various damper damping coefficient to the short building. The results showed improvement of seismic response of the tall building which was supported by short RC buildings through viscous damper device during earthquake. Moreover by increasing damper damping coefficient response of the tower structure the displacement was effectively reduced.