It is well known that torsional oscillations during an earthquake may cause severe distress in a building structure that is unsymmetric. All seismic codes therefore include some provisions for the design of structures to resist the forces induced by torsional vibrations. The torsion design provisions of a number of codes are reviewed and compared with a new set of design proposals. Results of elastic and inelastic response studies of a single storey building model show that the provisions of all of the codes studied are conservative for the design of resisting elements on the flexible side of the building. However, in some cases the code provisions may be unconservative for the design of resisting elements on the stiff side, particularly for buildings with a low value of torsional stiffness. The new provisions are seen to represent an improvement.
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