Abstract

A procedure is developed for including the effects of accidental torsion in seismic design of buildings. It has four steps. First, the ratio between the fundamental frequencies of uncoupled torsional and lateral motions of the building is computed. This ratio and plan dimensions are then used to estimate the increase in displacements at the edge of the building resulting from all sources of accidental torsion. Third, from these edge displacements the increase in displacements at the location of interior resisting planes are estimated. Finally, the design forces in structural members are computed by amplifying the forces ignoring accidental torsion by the increase in building displacements determined previously. This procedure has several advantages over the code-specified static and dynamic analysis procedures to include accidental torsion, such as: (1) The elimination of cumbersome static or three-dimensional dynamic analyses to account for accidental torsion effects in building design; and (2) the inclusion of the effects of all sources of accidental torsion. Two building examples are presented to illustrate these advantages as well as the computational steps required to implement the new procedure.