Structural Effects of Vertical Non‐Skeletal Elements (NSEs) With Rocking Mechanisms

ABSTRACT

This paper introduces the structural effects provided by vertical non‐skeletal elements (NSEs), such as claddings and partitions, with vertical slotted holes at their supports to enable rocking as the frame undergoes significant lateral deformation. Theoretical expressions for the recentring force provided by these rocking vertical NSEs, referred to as rocking elements or REs, were derived. A single‐storey model was analysed using cyclic push‐pull analysis considering different weight ratios, α , of the weight of REs to total system, and different RE installations, with and without the P‐ delta effect. The influence of these REs on drifts was investigated through time‐history analysis using a single ground‐motion record. Furthermore, parametric analysis using a suite of records was carried out to investigate the influence of the weight ratio, α , the post‐elastic stiffness ratio considering P‐ delta effect, r , and the lateral force reduction factor, R , on inter‐storey drift ratios (IDRs). Finally, the effects of REs in a practical five‐storey braced frame building were evaluated using cyclic push‐pull and time‐history analysis. It was found that the REs enhanced the performance by increasing the lateral strength and self‐centring tendency. Theoretical predictions of the effects of REs were consistent with cyclic push‐pull analyses. REs with higher weight ratios, α , and larger horizontal support spacing provided greater recentring forces. Time‐history analyses showed that structural peak and residual IDRs both decreased, especially in structures with a negative post‐elastic stiffness, such as may occur due to the P‐ delta effect. This reduction in IDRs was more pronounced with increasing weight ratio, α , and in those structures with more negative post‐elastic stiffness ratio, r , and higher lateral force reduction factor, R . For the five‐storey building with r = −0.018, the use of REs reduced median peak IDRs by over 25% and lowered median residual IDRs from 0.6% to below 0.04%, demonstrating a substantial enhancement in dynamic stability.