On the Characteristics of an Off-centre Bracing System

摘要

A particular off-centre bracing system (OBS) is introduced. In this system the tensile diagonal strut is not straight. Once the load is applied, the original geometry changes and, therefore, the load-deflexion of such a system becomes geometrically non-linear. An iterative method of analysis has been developed to study the non-linear load-deflexion behaviour of off-centre bracing systems (OBS). The results indicate that the stiffness increases with load and that the load-deflexion characteristics can be similar to that of hardening springs. The degree of non-linearity mainly depends on the eccentricity of the tension diagonal and the relative stiffness of bracing members. The non-linear characteristics of OBS were then considered as an effective expedient for mitigation of seismic loads. A non-linear program was developed to analyse seismic response of off-centre bracings subjected to various collapse-level earthquakes. The results indicate that OBS behave generally like base isolated systems and that the response may be reduced remarkably by pre-adjustment of eccentricity and relative stiffness of bracings.