Cyclic Behavior of Replaceable Steel Coupling Beams

Abstract

For improving the seismic resiliency of coupled shear wall systems, a type of replaceable steel coupling beam was developed, which consists of a central “fuse” shear link connecting to steel beam segments at its two ends. Inelastic deformation is concentrated in the shear link during a severe earthquake, and the damaged links can be replaced easily as specialized link-to-beam connections are adopted. This paper presents a series of quasi-static tests conducted to examine the seismic behavior and replaceability of the replaceable coupling beams. A total of four large-scale specimens were designed and tested, where different types of beam-to-link connections were adopted, including end plate, splice plate, bolted web, and adhesive web. All specimens fully developed the shear strength of the fuse links and showed large inelastic rotation capacity of no less than 0.06 rad, except for the specimen with the adhesive web connection, which failed at an early stage. The specimen with the end plate connection had inelastic deformation concentrated in the shear link, showing very stable hysteresis behavior. Slippage of high-strength bolts was observed at the splice plate and bolted web connections, which led to increased deformation and “pinching” in hysteresis loops of coupling beams. Interestingly, at a coupling beam rotation exceeding 0.01 rad, a large axial force developed in the steel coupling beams, the maximum value of which reached approximately a quarter to half of the axial yield strength of the shear link. In addition, on-site replacement of shear links was demonstrated after the coupling beam specimens experienced 0.02-rad rotation. The end plate connection was replaced within the shortest time, whereas the bolted web connection was able to accommodate the largest residual deformation.