Gravity well-inspired double friction pendulum system for bridges under pulse-like near-fault earthquakes

Abstract

When a coin is tossed to a gravity well, it will spiral instead of falling directly to the center. Inspired by this phenomenon, a gravity well-inspired double friction pendulum system (GW-DFPS) is developed to extend the length of sliding trajectories of bridge superstructures during pulse-like near-fault earthquakes. As a result, a greater amount of energy will be dissipated due to the frictional sliding of the isolators. The GW-DFPS consists of a spherical surface and an outer surface described by a 1/x or logarithmic function to build gravity well. Full-scale isolators were fabricated and their response was characterized considering various parameters such as the friction material of slider, surface roughness of sliding surfaces, and applied vertical loads. Additionally, a finite element model of the isolator was created using the experimental test data. Numerical simulations were performed on a case-study bridge structure isolated using both a conventional DFPS system and the proposed GW-DFPS systems. The experimental results reveal that the proposed isolators exhibit stable response under vertical loads varying from 200 kN to 1000 kN with a negative stiffness response when the isolator slides at the outer sliding surface. The numerical simulations of the selected bridge structure demonstrate that the GW-DFPS significantly extends the sliding trajectory lengths of the superstructure during half of the earthquake pulses, resulting in increased energy dissipation during this interval. The kinetic energies of the bridge isolated by GW-DFPS are consistently lower than those of the bridge isolated by the other two kinds of isolators, resulting lower shear forces on the bridge.

Keywords

Friction pendulum bearing / Gravity well / Trajectory / Earthquakes / Bridges

Relevance to resilience

The proposed Gravity Well-inspired Double Friction Pendulum System (GW-DFPS) has the potential to significantly enhance the seismic resilience of bridges, particularly under pulse-like near-fault earthquake conditions. This innovative system offers several key advantages: it maintains comparable self-centering capabilities to conventional DFPS with smaller radii, effectively reduces internal stresses within bridge substructures during moderate seismic events, and demonstrates superior energy dissipation performance specifically during the critical half-pulse phase of near-fault earthquakes.

Data availability statement

All data, models, and codes generated or used during the study appear in the published article.

CRediT authorship contribution statement

Sasa Cao: Writing - original draft, Software, Data curation, Conceptualization. Osman E. Ozbulut: Writing - review & editing, Conceptualization.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgments

This work was financially supported by the National Natural Science Foundation of China (Grants 52178124, 52478151).

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