SEISMIC ANALYSIS OF BUILDINGS INCLUDING TORSIONAL EFFECTS

Abstract

Torsional forces may be induced in a building during earthquake when the centre of mass does not coincide with the centre of rigidity. Torsion may occur in symmetric buildings also due to torsional component of ground motion, torsional mode of vibration of the building or non-uniform yielding of elements in inelastic range. The seismic codes of many countries have recognised the importance of torsion and made the necessary provisions. Provisions of accidental eccentricity even for symmetrical buildings have also been made in the seismic codes of several countries. IS 1893-1984 stipulates that design eccentricity shall be taken as 1.5 times the computed eccentricity and negative torsional shears shall be neglected. The comparison of codal provisions of various countries shows that the design eccentricity as proposed by the Seismic Code of the Federal Republic of Germany is the highest whereas the design eccentri-city as proposed by the IS code is the lowest . The provi-sion for accidental eccentricity is there in various countries while it is missing from the Indian code...