Seismic Behavior of Shear Keys Enhanced with Novel Energy Absorption Devices in Immersion Joints Based on Pseudo-Static Tests.

Abstract

Shear keys are usually installed as crucial shear-resistant members of an immersion joint; thus, the mechanical behavior of the shear keys, especially under earthquake loading, deserves more attention. This paper presents a novel arc-shaped energy absorption device developed for shear keys. In order to verify the seismic performance of shear keys strengthened by the arc-shaped energy absorption devices, a series of pseudo-static tests were conducted, in which different axial pressures (300 kN, 400 kN) were also taken into consideration. The testing results indicated that failure mode of the shear key enhanced by the energy absorption devices was a synthesis of the oblique shear failure of the rubber blankets, the buckling of the energy absorption devices, and the concrete fracture of the shear key. In view of load-displacement hysteretic curves of testing specimens, loops of the reinforced shear keys were plumper than those from a traditional shear key. In addition, the load-bearing capacity (cracking load, yield load, peak load, and failing load) differences of the shear keys with and without energy absorption devices reinforcement under the same axial pressure were 33.0%, 36.7%, 26.0%, and 23.6%, respectively. The maximum equivalent viscous coefficient values of the shear keys with and without energy absorption devices reinforcement were 0.37, 0.38, and 0.32, respectively. The arc-shaped energy absorption devices can contribute to the hysteretic behavior of the shear keys. However, the axial pressure had a positive influence on the load bearing capacity, accumulated energy absorption capacity, and initial stiffness of the shear keys. In contrast to that, the axial pressure had negative influence on ductility ratio of the reinforced shear keys (equivalent viscous coefficient values of two enhanced shear keys were roughly equal). A reasonable stiffness scheme of an energy absorption device should be given attention during the anti-seismic design of an immersion joint. The study can provide scientific support for further study on the seismic responses of immersion joints and promote the application of earthquake control technology in immersed tunnels.