Negative stiffness-enhanced seismic damping technology for an over-track complex with concrete-encased steel columns

The resilient transit-oriented model stimulates the necessity of seismic performance enhancement or retrofitting of over-track complexes with concrete-encased steel slender supporting columns. This study proposes a novel low-damping-ratio-based vibration control approach and easy-to-use design for over-track complexes by flexibly installing the negative stiffness amplification system (NSAS) at the multistory of the over-track building and lower podium. Moreover, a multilocationoriented design strategy and fitted formulae are developed for the NSAS-damped complex with enhanced energy-dissipation efficiency and an adjustable structural modal shape. By utilizing the negative stiffness device, dashpot, and tuning spring, the NSAS is theoretically constructed, and a simplified model of the NSAS-damped over-track complex is established. Stochastic response analysis and parametric investigation are performed to quantify the benefit of the NSAS-damped story over the conventional control method. Then, easy-to-use design formulae are provided in the initial design and parameter modification stages to realize the simultaneous control of the upper and lower structures. Based on a typical over-track complex with concrete-encased steel slender supporting columns, design cases are analyzed for the NSAS and conventional viscous dampers to verify the applicability of the proposed NSAS and design. The results indicate that the target-story located NSASs contribute a higher-efficiency approach to realize the significant performance improvement or retrofit of the over-track complexes without perturbing the daily function. Particularly, NSASs tailored for distinct stories in the over-track complex effectively satisfy the modification demand for structural modal shape and enhanced energy dissipation efficiency, which cannot be realized by conventional viscous dampers or the existing design of NSASs in normal buildings. In addition, the NSAS-damped story demonstrates a released stiffness abruptness and robust seismic performances against various earthquakes.