Novel external dissipative device for rocking bridge columns: Resilient rotational friction elements

Rocking columns with internal reinforcement face challenges such as inelastic buckling, fracture due to low-cycle fatigue, and complex repair processes, which can compromise their resiliency after seismic events. This paper introduces the resilient rotational friction element (RRFE), an innovative external dissipative device designed to overcome inherent limitations in these rocking columns. By integrating controlled rotational friction mechanisms and self-centering prestressed strands, the RRFE enables damage-free seismic energy dissipation with superior structural resilience. Experimental evaluation under monotonic and cyclic loading validated the RRFE's robustness and energy dissipation capabilities. Monotonic tests demonstrated the influence of torque levels on frictional resistance with friction energy increasing from 0.10 to 1.11 kips·in, reflecting an 11-time increase when transitioning from snug-tightened to a 40 lb·ft torque level. A mechanistic model developed from monotonic tests provides predictive accuracy for friction energy design. Additionally, a theoretical framework was established to derive the rotational moment (M_R) based on Coulomb's friction law and stress distribution principles. The developed equations, validated against experimental results, accurately capture the relationship between applied torque and axial post-peak behavior, providing a reliable tool for optimizing RRFE performance. Cyclic tests highlighted consistent energy dissipation and post-buckling performance across different specimens. Higher torque levels resulted in increased energy dissipation. The RRFE's adaptable design suits rocking systems such as concrete walls, steel columns, and mass timber walls, offering a cost-effective solution for new construction and retrofitting. This paper confirms the RRFE's potential as a transformative advancement in seismic-resistant design, addressing conventional system drawbacks and providing an efficient, repairable, and resilient solution for seismic-resistant structures.