Experimental study on integrated negative stiffness outriggers for high-rise buildings

This study proposes an innovative integrated negative stiffness outrigger (INSO) for high-rise outrigger-core tube structures. INSO incorporates negative stiffness devices (NSDs) arranged bilaterally on both sides of the outrigger truss while maintaining viscous damper arrangements in conventional damped outriggers. This configuration enables efficient integration into both new and retrofitted outrigger-core tube structures, providing a practical engineering solution for realizing negative stiffness damped outrigger systems. The feasibility of INSO is validated through dynamic testing of a conceptual prototype and quasi-static testing of a 1:8 scaled substructure specimen incorporating frame beams and a perimeter column. A simplified analytical methodology is developed to determine key NSD parameters. Results demonstrate that INSO offers a space-efficient layout with robust dynamic performance. The simplified formula for initial negative stiffness shows minimal error, while stiffness transition displacement errors (2–20 %) show an inverse correlation with spring pre-compression. Considering the NSDs’ influence on outrigger mechanical behavior and the requirement to maintain transition displacement errors below 10 %, a spring pre-compression ratio exceeding 0.25 is recommended. • A novel integrated negative stiffness outrigger (INSO) is proposed. • INSO layout avoids lever constraints and prevents extra forces on outer columns. • INSO shows inverse S-shaped hysteresis and remains stable under high-frequency loads. • Simplified formulas for NSD stiffness and transition displacement are proposed and verified for use.