COMPARATIVE ANALYSIS OF VERTICALLY IRREGULAR STRUCTURES IN DIFFERENT SEISMIC ZONES”- A LITERATURE REVIEW

Abstract

Past earthquakes in India have revealed that majority of the buildings are not designed to be earthquake resistant. Generally, buildings are designed taking into account only the gravity loads. Also, the current design seismic codes are not fully practiced while designing a building. Hence, a higher degree of damage may be expected during an earthquake if the seismic resistance of the building is inadequate. This work is concerned with the effects of various vertical irregularities on the seismic response of a structure. Study of the comparison of the results of analysis of irregular structures with regular structure was done. The scope of the project also includes the evaluation of response of structures subjected to high, low and intermediate frequency content earthquakes using response spectrum analysis. Different types of irregularities namely mass irregularity, stiffness irregularity and vertical geometry irregularity were considered. Tall structures were found to have low natural frequency hence their response was found to be maximum in a low frequency earthquake. It is because low natural frequency of tall structures subjected to low frequency earthquake leads to resonance resulting in larger displacements. If a high rise structure (low natural frequency) is subjected to high frequency ground motion then it results in small displacements. Similarly, if a low rise structure (high natural frequency) is subjected to high frequency ground motion it results in larger displacements whereas small displacements occur when the high rise structure is subjected to low frequency ground motion. The complex shaped buildings are now days getting popular, but they carry a risk of sustaining damages during earthquakes. Therefore, such buildings should be designed properly taking care of their dynamic behaviour.