Simplified relations for the application of rotational components to seismic design codes

In this paper, after reviewing the characteristics of earthquake rotational components, the acceleration response spectra of rocking and torsional components are presented. In addition, the proposed relations in the author’s previously published paper on the rotational loading of structures are extended, and application of the new relations is examined. The numerical results of this study show that the contribution of earthquake rocking components to the rotational loading of multistory buildings is strongly sensitive to structural irregularity, structural height and seismic excitation. The rocking component contribution to story shear can be one-third of the horizontal component contribution, and should be included in seismic design codes. Further, the value of the eccentricity of 0.05 plan dimension, which is prescribed in the most current seismic design codes for accidental torsional effects, is not a conservative approximation for the accidental eccentricity caused just by the influences of the torsional component, particularly in symmetric, torsionally stiff, multistory buildings.