Composite floor slab effect on seismic performance of steel-framed-tube structures with shear links

High-strength steel-framed-tube structures with low-yield-point shear links (SFT-RLYPSL) exhibit exceptional lateral and torsional stiffness, coupled with significant energy dissipation capacities. This study aims to investigate teh influence of composite floor slabs on the seismic performance of these structures. Expanding on previous research concerning SFT-RLYPSL, this paper presents a simplified numerical model for the SFT-RLYPSL, incorporating the influence of the composite floor slab. The developed model employs the steel4 constitutive relation to accurately depict the behavior of low-yield-point steel. Furthermore, the simplified numerical model utilizes two-node link elements to simulate shear links and integrates composite beams to represent the influence of the composite floor slab. Using this simplified model, elastic-plastic pushover analysis is performed on five distinct SFT-RLYPSL structural cases, and nonlinear time-history analysis is conducted on three structural configurations. The investigation explores various aspects of the seismic performance of SFT-RLYPSL, including modal behavior, pushover curves, progression of overturning failure, time-history roof displacements, inter-story drift angles, base reactions, inter-story shear, failure modes, residual inter-story drift angles, and the manifestation of shear lag phenomena. The findings suggest that incorporating the composite floor slab effect enhances initial stiffness and peak load capacity in pushover analysis, leading to distinct three-stage pushover curves. During nonlinear time-history analysis, the composite floor slab effect increases structural stiffness, decreases roof displacements and inter-story drift angles, while simultaneously increasing base reactions, worsening component damage, and raising collapse risk. Nevertheless, its influence on residual inter-story drift angles remains relatively minor, with a mitigating effect on the shear lag phenomenon. Importantly, the degree of this impact varies with alterations in floor slab thickness and seismic intensity, highlighting the critical importance of considering the composite floor slab effect in structural design deliberations.