Investigation on seismic damping effect of an innovative amplified viscously damped outrigger for super high-rise structures

AN innovative amplified viscously damped outrigger (AVDO) is newly proposed to improve the seismic damping effect of conventional viscousl damped outrigger (VDO) on super high-rise structures by mechanically increasing the displacement of the viscous damper (VD). To investigate the advantages of the damping effect on AVDO over VDO, the dynamic cyclic tests on VDO and AVDO were conducted to verify the feasibility of AVDO and superiority of AVDO over VDO. On this basis, six finite element models of a 258 m-high building with two types of damped outriggers placed at different heights were established and analyzed by dynamic time-history method. By comparing the seismic responses of numerical models, it is shown that upgrading VDO to AVDO can improve the damping efficiency of VDs and effectively expand the applicable damping placement in structural height, thus, the structure can achieve a better damping effect. An equivalent theoretical model of AVDO was established and validated by numerical analysis, which contributes to facilitating the modelling work and analysis of AVDO. However, experimental results showed that the outrigger deformation reduced the working displacement of VD seriously, indicating that the stiffness of the outrigger should be designed reasonably to withstand the damping force in motion. On this basis, the relationship between the working efficiency of VD and the stiffness ratio of outrigger to VD was derived and verified. To ensure the high work efficiency of the damper, the recommended stiffness limit of the outrigger supporting nonlinear VD was put forward, which fills a gap in the specification for practical applications.