Concept and Behavior of a Steel Ring Restrainer with Variable Stiffness and Buffer Capacity

Abstract

In this paper, a novel restrainer called steel ring restrainer (SRR) is proposed to prevent the unseating of bridges. The restrainer is comprised of a steel ring, an upper guiding pulley, a downward guiding pulley, and two connections. The SRR can provide different stiffnesses under different seismic excitations. The SRR is not activated under daily load but provides smaller stiffness in small and medium earthquakes and even larger stiffness in strong earthquakes. The stiffness changes smoothly from small and medium earthquakes to strong earthquakes. This mechanism called buffer capacity reduces the impact on the connection between the SRR and structure. In order to study the effect of each design parameter on the mechanical properties of the SRR, 54 finite element (FE) models in four groups were established and analyzed. The results show that the diameter of the cross-section of the steel ring has an important influence on the initial stiffness, secondary stiffness, buffering capacity, and ultimate bearing capacity of the SRR, the radius of the curved part of the steel ring significantly affected the initial stiffness and ultimate displacement, the nonworking length of the SRR was decided by the length of the straight part of the steel ring, and the diameter of the guide pulley governed the ultimate bearing capacity and ultimate displacement. Additionally, the predicted formulas of the design parameters were derived and eight models were employed to investigate the effectiveness of the formulas, in order to be applied in the seismic design.