EARTHQUAKE RESISTANT DESIGN OF RC BUILDING CONSIDERING EFFECT OF SOIL-STRUCTURE INTERACTION

Abstract

Reinforced Concrete (RC) buildings are conventionally analyzed and design for gravity loads and other imposed loads. Such buildings possess adequate strength and stiffness to resist these vertical loads but don't have adequate strength and stiffness when subjected to additional lateral loads. Incorporation of seismic forces in the design of RC building ensures greater safety levels for occupant in the advent of any seismic disturbance. The level of additional forces exerted on the building depends upon the seismic zones and the type of soil profile existing in that region. For a particular RC building, the magnitude of the lateral loads due to earthquakes will depend on the seismic zone in which the building is located and the type of soil upon which the building is supported, the importance factor and response reduction factor. The variation in these factors will influence the magnitude of lateral loads affecting the size of structural members like beams, columns and foundation, which in turn, will influence the response of the building during earthquake. When RC building is founded on the hard soil, the foundation is considered as fixed. However, when the same building is supported by either medium soil or soft soil, the foundation cannot be considered as fixed. In these cases, the flexibility of the foundation has to be considered through the Soil-Structure Interaction (SSI) effect. A four storey RC building has been analyzed and design for seismic zones IV and V supported by Type I, Type II and Type III soils [14]. The buildings are analyzed and designed with and without SSI effect. The structural cost, i.e., the cost of the structural steel and the cost of the concrete have been computed and the comparisons of the structural costs have been done. Ten RC buildings having the same plan geometry and the height have been analyzed and designed.