ACCIDENTAL TORSION ANALYSIS IN FRAMED BUILDINGS

Abstract

Building frames have to be designed to resist torsional moment that may arise during an earthquake. A structure may face torsional forces due to planned eccentricity or due to ecciden causes. This study predominantly focusss on later aspect. Many codes of practice incorporate accidental torsion by including an additional eccentricity in the design & eccentricity calculations.The analysis is then done using a purely state method. In this study a mass perturbation methodology is discussed and employed for anlysing buildings for accidental torsion. Mass perturbation alters the mass distribution thereby creating an additional eccentricity. The building is then analysed using a dynamic method. Two example buildings are analysed one symmetric and the other asymmetric. Comparisions are made using mass perturbation methodology and static torsional analysis. It is concluded that a static torsional analysis may not be good enough and the mass perturbation method should be used.