Research Projects

Most seismic standards recommend shifting the lateral load profile by an offset called 'accidental eccentricity' on either side of the floor center of mass (CM) to account for the contribution of torsional ground motion. However, dynamic analysis is felt mandatory for not-so-regular structures, as it invites directional coupling in mass participation and higher mode participation. None of the standards explicitly recommend the procedure for implementation for the accidental eccentricity in time history analysis. This proposal builds upon the principal investigator's alternate definition of accidental eccentricity and aims to develop design recommendations. A pair of horizontal components and a torsional component (referred to as 3-component) recorded over Kefalonia seismic array in about 150 events will form the basis of ground motion inputs in this proposal. Several one-story systems will be analysed with i) 3-component excitations and ii) horizontal pair of excitations with accidental eccentricity, which will be repeated with increasing accidental eccentricity until the seismic demand from the former is met. The required accidental eccentricity will also account for the directionality and aleatory variability of the ground motion. The proposal will extend the framework to multistorey systems using the principle of structural dynamics. Required accidental eccentricity for a given multistorey system can be extracted using its modal properties from the recommendations of the one-storey system. The proposal will also investigate the effect of yielding of structural system elements on the accidental eccentricity and its possible inclusion in the design recommendations.