Dynamic Characteristics and Responses of Damped Outrigger Tall Buildings Using Negative Stiffness

By introducing negative stiffness devices, this study further improves the maximum achievable damping ratio of conventional damped outrigger (CDO) structures with flexible perimeter columns. Dynamic characteristics of tall buildings with this novel negative stiffness damped outrigger (NSDO) are parametrically studied by solving the transcendental characteristic equations. An NSDO is able to improve the maximum achievable damping ratio to about 30% with less consumption of an outrigger damping coefficient (or a less amount of a viscous damper) as compared with a CDO. Numerical results showed that the NSDO is effective for both winds and earthquakes. For instance, an NSDO further decreases the maximum seismic interstory drift by 18.9% and reduces the total-wind-excited acceleration by 34.9%, with only a 20% outrigger damping consumption, as compared to a CDO. Because neither an NSDO nor CDO provides extra stiffness at low amplitudes of motion, an extra conventional outrigger (CO) is suggested to be placed at the top of a tall building when applying an NSDO in practical applications, and the effectiveness of an NSDO is also not compromised when an extra CO is placed.