Many researchers have studied the natural
torsion of buildings subjected to earthquake ground motions, but only a few of
them studied the accidental torsion. The increase in response in the flexible
and the stiff edges of the building due to accidental torsion is investigated in
this study, using both static and time history analyses. The accidental torsion
is introduced by the accidental eccentricity provided in the Moroccan seismic
code: RPS2000 version 2011. Based on the results of the time history analyses,
a new practical method is proposed to assess the maximum increase in response
due to accidental torsion. This method is generalized to a certain category of
multi-storey buildings and presents the main advantage to avoid performing many
extra seismic analyses as required in the current method of the Moroccan
seismic code. The new proposed method is limited to the elastic domain to be
compliant with the design procedure of the Moroccan seismic code. Further
studies have to be performed to assess the efficiency of the elastic seismic
design procedure that guaranties that the building will reach the required
seismic level of performance by inelastic deformations.
Keywords: Accidental torsion, eccentricity, frequency ratio, earthquake, Morocco.