Seismic behaviour of offcentre bracing systems

A geometric and material nonlinear model has been applied to the analysis o f a particular offcentre bracing system (OBS). The introduction of an off-d iagonal eccentricity in these systems results in a geometrically nonlinear behaviour. A displacement based iterative approach has been devised and imp lemented for hysteretic analysis of OBS with geometrical and material nonli nearities. The results of the analysis indicate that the load-deflexion beh aviour of OBS follows a nonlinear stiffness-hardening pattern with two yiel ding points, which reflect the tensile failure of different bracings. This analytical algorithm was incorporated in a dynamic programme, used for the dynamic and seismic analysis of single-storey and multistorey OBS. The resu lts indicate that OBS can be designed to behave like a base isolation syste m, with adequate reserved strength, to safeguard against instability in col lapse level earthquakes. (C) 1999 Elsevier Science Ltd. All rights reserved .