Fibre-based model for dynamic analysis of high-rise mega-braced frame-core building systems

In this paper, a broad set of nonlinear dynamic finite element simulations is presented and discussed to highlight specific trends and behavioural aspects in the seismic response of modern high-rise mega-braced frame-core buildings, the slenderness of which plays a key role in structural design and performance. In this study, 45- and 75-storey 2D frames were extracted from 3D case-study structures featuring an internal symmetric two-way braced core. These frames were designed in accordance with European seismic provisions. The numerical analysis was performed using inelastic force-based fibre elements to model structural members. Additionally, mechanical idealisations were introduced to accurately reproduce the behaviour of bolted beam-to-column joints and welded gusset plate connections. Out-of-plane imperfections of braces were explicitly included in the simulation to permit potential buckling mechanisms in both braces and gusset plates. Overall performance of mega-frame systems and key structural components was investigated, and the effects of bracing systems and outriggers/belt trusses were quantified. Sensitivity to the height of the structure was explored, comparing the response of the two case-study archetypes examined, and a paradigm was developed to relate the behaviour observed using different types of analysis.