Performance-based seismic analysis on a super high-rise building with improved viscously damped outrigger system

To investigate the seismic performance of a kind of improved viscously damped outrigger (IVDO) system, 6 elastoplastic models of a super high-rise building (729m) with multi-IVDOs located at different heights have been established using PERFORM-3D. Then, elastoplastic analysis on these models is carried out under 3 levels of earthquakes, namely, frequent, basic, and rare earthquakes. Comparison results of interstory drift, top displacement, base shear and overturning moment, additional damping ratio, maximum ratio of demand to capacity and other related indexes, and seismic performance assessments show that structure with IVDOs put at its lower height has larger additional damping ratio, smaller drift, and slighter degree of damage when it suffers from frequent and basic earthquakes. Reasonable damping ratio of building with IVDOs locating at lower height can also be achieved when rare earthquakes happen. Additionally, as belt truss is usually set at the same story where outrigger truss locates at to form closed spatial structure for better integrity, it is suggested belt truss at story where the IVDO locates or between 2 IVDOs should be optimized in case of premature bulking during earthquakes. It should also be noted that the IVDO can well reduce base overturning moment and have satisfactory control on base shear force and top displacement under basic and rare earthquakes, which is especially true in structure with IVDO installed at its lower height.