Practical calculation of the torsional stiffness radius of multistorey tall buildings

Abstract

The present paper refers to the definition of the torsional stiffness radii of multistorey tall buildings using both the continuous and the discrete model of the structure. The magnitude of the torsional stiffness radius of a building is the most important structural characteristic in order to explain the torsional behaviour of a building during an earthquake as it directly affects the building's torsional flexibility. The importance of the torsional flexibility of buildings is recognized by contemporary Seismic Codes that propose a grid of torsional provisions in order to avoid soft-storey operation due to floor torsional vibrations around a vertical axis. However, contrary to single-storey buildings, the torsional stiffness radius of multistorey buildings is not defined directly because both the translational and torsional stiffness of these buildings are expressed in matrix form. In the present paper, this weakness has been overcome using the continuous model of the structure, from which the torsional stiffness radius of a general monosymmetric multistorey tall system arises via a closed mathematical equation. The discrete model of the structure has numerically verified this closed mathematical equation. Copyright © 2007 John Wiley & Sons, Ltd.