The Effect of Seismic Design Methods on Design Eccentricities in Building with Planar Irregularities

Seismic provisions have utilized design eccentricities to reduce planar irregularities in lateral stiffness of buildings. In calculating a design eccentricity, the dynamic amplification factor may be applied either to accidental eccentricity or to both inherent and accidental eccentricities according to design codes. In this paper, different code provisions and their impact on torsional responses of buildings are investigated using example buildings with various aspect ratios and eccentricities. It was found that dynamic amplification is underestimated if the inherent eccentricity is small, when buildings are designed by seismic provisions using dynamic amplification factors for both to inherent and accidental eccentricities. On the other hand, the design eccentricity determined by applying the dynamic amplification factor only to accidental eccentricity reflects torsional amplification accurately.