SEISMIC ANALYSIS OF MULTISTOREYED BUILDINGS

Abstract

Earthquakes are catastrophic events ' that bring loss of lives as well as wealth. The structures that are designed without considering the effects of earthquakes, in earthquake prone zones, are dangerous ° in this respect. The analysis of structures considering the earthquake loading = becomes a little more costlier than the static analysis. But this is only a small price that is to be paid for the safety of structures and their users. Multistoreyed buildings are of prime importance among the structures that have to be designed for the dynamic loading. Keeping this point in view in this thesis, the static and dynamic analyses have been carried out on the mathematical models of taking into account the flexibility of the soil. (i.e., soil-structure interaction). It has been found from the analyses that the time periods of the buildings increase when the flexibility of soil is taken into account, in comparison of fixed base analysis. The damping of the structure is very less of the order of 5% to 10%. But the damping of the soil is very high, generally 20% to 50%. In soil-structure interaction method of analysis a realistic damping factor for the soil-structure combination is considered in the form of weighted damping ratio. This way the analysis of the structure becomes more reasonable and reliable. The study also indicates that structures designed on soil with lower shear wave velocity, will behave in more flexible manner and for the shear wave velocity (z 600 m/s) the structures behave in a rigid manner. (iv) P