Conventional fixed-base analysis ignoring the effect of soil-flexibility may result in unsafe design. Therefore, to evaluate the realistic behavior of structure the soil structure interaction (SSI) effect shall be incorporated in the analysis. In seismic analysis, provision of bracing system is one of the important option for the structure to have sufficient strength with adequate stiffness to resist lateral forces. The different configuration of these bracing systems alters the response of buildings, and therefore, it is important to evaluate the most effective bracing systems in view point of stability against SSI effect. In present study, three RC building frames, G+3, G+5 and G+7 and their respective scaled down steel model with two types of steel bracing system incorporating the effect of soil flexibility is considered for experimental and analytical study. The analytical study is carried out using Elastic continuum approach and the experimental study is carried out using Shake Table. The influence of SSI on various seismic parameters is presented. The study reveals that, steel bracing system is beneficial to control SSI effect and it is observed that V bracing is more effective, in resisting seismic load considering SSI.

Seismic Response of Steel Braced Building Frame Considering Soil Structure Interaction (SSI): An Experimental Study

Study and analysis of pile foundation supported on sandwich soil strata under dynamic condition

The significance of incorporating soil-structure interaction (SSI) effect in the analysis of building frames is increasingly recognized but, still not penetrated to all the level owing to various complexities involved in the modeling of SSI. The SSI effect considerably influences the design of multi-storey buildings situated in the seismic zone. Hence, there is a need to incorporate certain elements in the structure which will counterbalance the effect of SSI. The provision of shear walls is one of the potential option as these acts as major earthquake resisting element and also, increases the overall stiffness of the structure. The geometrical configuration of these shear walls alters the response of buildings, and therefore, it is important to evaluate the most beneficial locations of the shear walls. In present study, multi-storey reinforced concrete framed buildings of different heights with shear wall at five alternate locations in the building incorporating the effect of soil flexibility is considered to investigate the effectiveness of shear walls to control SSI. The study is carried out using Winklerian approach. The study reveals that, shear walls play important role to control SSI effect and very effective when placed centrally, near to centroid of building in resisting seismic load.

http://inpressco.com/wp-content/uploads/2015/10/Paper513372-3377.pdf

Effect of Shear Wall in the Seismic Analysis of Building Frames Considering Soil Structure Interaction-A Study by Winklerian Approach

The effect and behaviour of soil - framed-structure interaction (SSI) under dynamic load conditions are presented in the paper. All civil engineering structures involve various types of structural elements that are in direct contact with soil. Hence, a new thin-layer interface element, based on the concept of the finite element method, is formulated. The formulation is elaborated using a combination of degrees of freedom of the top and bottom sides of the interface elements. The compatibility conditions of displacements between beam elements and quadrilateral soil elements are applied. Thus, a numerical program integrating the thin-layer interface element is developed for this purpose. The obtained results show that interaction between the soil and a framed structure has a considerable influence on the structural dynamic response of system components. Additionally, a parametric study has been elaborated to quantify the significance of interface behaviour on the soil and on the framed structure under dynamic load.

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Effects and dynamic behaviour of soil - framed structure interaction

The response of a structure under earthquake loading is directly associated with the response of soil to ground shaking. Thus, the extent and degree of damage during an earthquake is mainly influenced by the response of soil to ground vibrations. Therefore, it is vital to evaluate the response of soil due to ground vibration. Though the structures are supported on soil, most of the designers do not consider the soil structure interaction and its subsequent effect on structure during an earthquake. Different soil properties can affect seismic waves as they pass through a soil layer. When a structure is subjected to an earthquake excitation, it interacts the foundation and soil, and thus changes the motion of the ground. It means that the movement of the whole ground structure system is influenced by type of soil as well as by the type of structure. The present study is an effort towards analysis of the structure during the earthquake. G+10 stories residential building is considered. To study various parameters such as shear force, bending moment, storey drifts, storey shear, lateral displacement.

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Seismic Response of Multistoried Building Considering Effect of Cohesive and Non-Cohesive Soil

The seismic response of a structure is greatly influenced by Soil Structure Interaction (SSI). In this study the effect of soil flexibility on the performance of building frame is investigated. Two SSI modes are considered for the analysis; one is replacing soil by spring of equivalent stiffness (Discrete Support) and second by considering the whole soil mass (Elastic Continuum). Symmetric space frames resting on isolated footing of configurations 2 bay 2 storey (2X2X2), 2 bay 5 storey (2X2X5) and 2 bay 8 storey (2X2X8) are considered with fixed base and flexible base. The spring model is developed by using stiffness equation along all 6 DOF and elastic continuum model is developed by Finite Element Method using SAP-2000. For SSI study three types of soil are considered i.e. Hard, Medium Hard and Soft Soil. The dynamic analysis is carried out using Response Spectrum, given in IS1893-2002. The influence of soil structure interaction on various structural parameters i.e. natural time period, base shear, roof displacement, beam moment and column moment are presented. The study reveals that the SSI significantly affects on the response of the structure. Finite Element Method has proved to be the effective method for consideration of elastic continuum below foundation.

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S. A. Halkude

Papers

Soil Structure Interaction Effect on Seismic Response of R.C. Frames with Isolated Footing