Seismic Performance of an Axial‐Released Outrigger System to Reduce the Effects of Core Wall Elongation on Damper Demands in Reinforced Concrete Buildings

In damped outrigger buildings, the intended lateral mechanism relies on balanced tension and compression forces in opposing dampers. However, axial elongation of reinforced concrete (RC) shear walls under cyclic lateral loading can disturb this balance and alter the lateral response mechanism. This study proposes an axial‐released outrigger system (AROS) to mitigate the undesirable effects of wall elongation in tall concrete buildings. In the AROS configuration, vertical compatibility between the core wall and the outrigger truss is released, allowing wall elongation to occur without imposing additional vertical deformation and unintended demands on the dampers. A 40‐story building representative of Vancouver practice is designed, and a parametric study is conducted using fourteen prototypes that consider different core wall nonlinear mechanisms, damper capacities and outrigger system types (conventional damped outrigger system, CDOS, and AROS). Detailed nonlinear models are developed in OpenSees, and the prototypes are assessed using pushover analysis and nonlinear time‐history analysis (NLTHA) at serviceability and design hazard levels. Results show that AROS maintains more balanced forces in opposing dampers and reduces excessive tensile demands, which in turn significantly lowers the likelihood of damper rupture. Compared with CDOS, AROS demonstrates more stable and predictable nonlinear behaviour, improved damper utilisation and better control of serviceability‐level responses. The findings also indicate that comparable global seismic performance can be achieved with smaller damper capacities when AROS is used, highlighting its potential for improved design efficiency. Overall, the proposed AROS configuration provides a practical solution for mitigating wall elongation effects and achieving behaviour closer to the intended lateral mechanism in damped outrigger buildings.