Weak‐Story Mitigation and Drift Redistribution in Moment‐Resisting Frames Using Stepping Rocking Walls

ABSTRACT This study investigates the seismic response of moment‐resisting frames retrofitted with a stepping rocking wall, with emphasis on weak‐story mitigation and residual drift reduction under both ordinary and pulse‐like ground motions. Nonlinear response‐history analyses are conducted on 9‐story and 20‐story SAC Los Angeles frames. The results show that the unretrofitted frames develop concentrated drift demands and significant residual deformations, particularly in the taller system. Introducing the stepping rocking wall modifies this behavior by enabling uplift and recentering, which promotes a first‐mode‐dominated response and suppresses higher‐mode‐induced drift concentration. As a result, story drift demands are redistributed along the height, reducing drift concentration and limiting the formation of weak‐story mechanisms. To quantify this effect, a drift concentration factor (DCF) is employed as a scalar measure of drift localization across ground motions, addressing the limitation of peak story drift as a global response metric. The results show consistently lower DCF values in the retrofitted systems, confirming reduced drift localization and improved deformation distribution. Additional analyses using pulse‐like ground motions scaled to the maximum considered earthquake (MCE) level show that these beneficial trends persist under increased shaking intensity, with substantial reductions in peak interstory drift, residual drift, and drift concentration in both buildings. The findings demonstrate that stepping rocking walls not only reduce peak and residual demands, but also fundamentally alter the distribution of seismic deformation, providing a mechanism for mitigating weak‐story behavior and improving post‐earthquake repairability.