Dual Transitional Floors and Soil-Structure Synergy: A Paradigm Shift in Seismic Resilience for Hybrid High-Rise Systems

Hybrid high-rise systems combining steel and concrete components offer enhanced seismic resilience, yet the interplay between transitional floors and soil-structure interaction (SSI) remains underexplored in design practices. This study evaluates the seismic performance of 20- and 25-story hybrid structures with dual transitional floors, integrating steel-braced upper sections and reinforced concrete lower floors, while accounting for SSI effects. Linear and nonlinear dynamic analyses, including incremental dynamic analysis (IDA), were conducted using ABAQUS and ANSYS to assess lateral displacement, base shear, and stress distributions. Results demonstrate that dual transitional floors reduce lateral displacement by about 20% compared to single-transition systems, attributed to improved load redistribution and energy dissipation. However, SSI amplified roof displacements by up to 40% and reduced base shear by 12%, underscoring its critical role in seismic assessments. Stress concentrations at transitional joints increased by 5.5%, highlighting vulnerabilities requiring retrofitting. Finite element analysis revealed SSI amplifies plastic-region displacement demands, emphasizing the need for nonlinear modeling. Optimal transitional floor placement in the upper third of the structure balanced axial forces and minimized shear stresses, enhancing overall stiffness. The study concludes that dual-transition systems improve seismic resilience, but SSI necessitates probabilistic assessments and advanced damping strategies in design codes. These findings advocate for integrating SSI and transitional floor optimization in hybrid structural frameworks for seismically active regions.