This study presents a novel seismic control system, the Mega-Sub Controlled Structure System (MSCSS), to address vibration control challenges in tall and super-tall buildings under intense seismic excitations. The proposed hybrid VD-TFPB-controlled MSCSS integrates Triple Friction Pendulum Bearings (TFPBs) as base isolators with Viscous Dampers (VDs) between the mega frame and the vibration control substructure, enhancing damping and seismic performance. MSCSS without VD and MSCSS with VD models are established and verified using an existing benchmark. The hybrid VD-TFPB-controlled MSCSS is then developed to evaluate its vibration control response while considering soil-structure interaction (SSI). Numerical analyses with earthquake records demonstrate its superior performance compared to MSCSS without and with VD systems. Nonlinear dynamic analyses reveal that the hybrid system significantly improves vibration control. However, under SSI, increased structural flexibility leads to higher frame stress and more plastic hinges, particularly on soft soil, which amplifies vibrations. Despite these challenges, the hybrid VD-TFPB-controlled MSCSS effectively enhances seismic resilience, offering a robust solution for tall buildings.

Designers often assume a rigid foundation for buildings in seismic zones, believing it ensures safety during earthquakes. However, this assumption may neglect important factors, such as soil-structure interaction (SSI) and the potential for collisions between adjacent buildings. This study investigates the effect of dynamic SSI on the seismic pounding response of adjacent buildings. A nonlinear finite-element analysis was performed on three cases: bare buildings, buildings with linear fluid viscous dampers (LFVDs), and buildings with nonlinear fluid viscous dampers (NFVDs). The dynamic contact technique, in which contact surfaces with both the contactor and target, was employed to mimic the mutual pounding. Key seismic response parameters, including acceleration, displacement, inter-story drift, and pounding forces, were analyzed. The results showed that dynamic SSI significantly affects the seismic performance of adjacent buildings, altering the number, timing, and intensity of collisions. In some cases, SSI increased inter-story drifts beyond code-permissible limits, indicating that relying on a rigid foundation assumption could lead to unsafe structural designs. Additionally, SSI had a notable impact on the forces in NFVDs, highlighting the need for careful design considerations when using these devices. The study further investigates the effect of soil flexibility on the performance of nearby structures under different seismic excitations, focusing on the NFVDs case with a 10 % damping ratio. Incremental Dynamic Analysis (IDA) and fragility analysis were conducted to assess performance under seismic excitations, focusing on three performance levels: Immediate Occupancy (IO), Life Safety (LS), and Collapse Prevention (CP). While SSI had minimal impact on the more flexible buildings, it significantly affected the more rigid building, particularly at LS and CP levels, making it more vulnerable to damage compared to buildings on rigid foundations. These findings underscore the importance of incorporating SSI in seismic design to ensure structural safety.