Enhanced Elongation Self-Centring Link with Variable Stiffness for Coupled Walls

This study develops an enhanced elongation self-centring link with variable stiffness (ESCL-VS) for coupled walls by combining disc springs and tendons in a series-like configuration to enhance deformation capacity and prevent tendons from prematurely entering plasticity. The constraint mechanism, which limits the deformation of the disc spring, induces stiffness hardening within the link system, thereby controlling the structural displacement response under large deformations. First, the structure and expected nonlinear behavior of the ESCL-VS are introduced. Subsequently, pseudo-static tests were conducted, revealing that the deformation capacity of ESCL-VS increased by 250% and 167% compared to self-centring link-1 (SCL-1) and self-centring link-2 (SCL-2), respectively. Furthermore, the ESCL-VS exhibited no residual deformation under large story drift, outperforming SCL-1 and SCL-2, which demonstrated considerable residual deformation. Finally, a comprehensive numerical study was conducted to examine various parameters affecting the behavior of ESCL-VS. The results indicate that the initial tendon stress, frictional slip force, and tendon material significantly influence the overall connection behavior. The stiffness ratio between the disc spring and the tendon affects the deformation capacity of the ESCL-VS, with a well-designed ratio providing sufficient deformation capacity while controlling displacement under large deformations.