Pendulum column with inclined negative stiffness as a novel hybrid seismic isolation mechanism integrated into soil with pile-like characteristics

Earthquakes caused major structural damage, prompting the development of seismic isolation techniques. On the other hand, building structures on weak soils poses many challenges due to their lack of bearing capacity and inappropriate behavior in the long term and during earthquakes. This study introduces a new QZS device called the Pendulum Column with Inclined Negative Stiffness (PC-INS) which increases the system’s natural period, enhancing isolation performance. A key advantage of PC-INS is its cylindrical outer shell, which acts as a pile when embedded in soil. This feature significantly improves performance in weak or inappropriate soil. Overall, PC-INS offers a promising solution for effective seismic isolation in both standard and challenging geotechnical environments. A model was analyzed using multiple earthquake records in MATLAB and validated through finite element modeling in ABAQUS. The soil-structure interaction was studied and a 3D model was developed to investigate the stress distribution. Results demonstrate that PC-INS reduces both acceleration and displacement. The system also performs reliably with minimal damping (5%). FFT analysis confirmed the absence of resonance in almost all analyzed earthquakes. The input energy analysis demonstrated the effectiveness of the system. Proposed hybrid pile demonstrates a significant reduction in responses generated in the soil. The structural model revealed a considerable reduction in the structural response when the proposed hybrid pile-isolator were employed.