THE SEISMIC COEFFICIENT METHOD IS SIMPLER THAN THE MODAL ANALYSIS METHOD WHICH INVOLVES THE KNOWLEDGE OF STRUCTURAL DYNAMICS.

EARTH QUAKE LOADS :-- Earthquake or seismic load on a building depends upon its geographical location , lateral stiffness and mass, and is reversible. Its effect should also be considered along both axis of a building taken one at a time.However ,wind loads and earthquake loads are assumed not to act simultaneously. Therefore a building should be designed for only one of the two loads whichever is critical . The analysis of a building for earthquake loads is done in accordance with IS: 1893 --1984 .A building may be analysed either by seismic coefficient method method method or by response spectrum (or modal analysis or spectral acceleration) method .The seismic coefficient method is simpler than the modal analysis method which involves the knowledge of structural dynamics .The first step in the seismic analysis is to determine the horizontal shear at the base of a frame which is also known as a base shear .Any of the two approaches could be used for buildings not exceeding 40 mt in height .For taller buildings, water towers ,stacks and stack - like structures,the spectral acceleration approach is suggested.