Steel Coupling Beams with a Replaceable Fuse

Abstract

Steel coupling beams have emerged as a viable alternative to conventionally and diagonally reinforced concrete coupling beams because of their superior energy-dissipation characteristics, smaller member depth, and ease of construction, to name but a few advantages. Conventional steel coupling beams are designed to yield under design-level ground motions; hence, postevent repair requires replacement of the entire beam that is embedded into wall piers and interfaced with a significant amount of wall pier reinforcement. Such a repair will be costly, intrusive, and very likely impractical. A new system involving a replaceable midspan fuse located in the coupling beam was developed. In this system, the fuse acts as the primary energy-dissipating component, while the remainder of the beam span and its embedments into the wall piers remain elastic when the building is subjected to design-level ground motions. Hence, it is only necessary to replace the accessible damaged fuses since the rest of the beam and wall piers remain undamaged. This paper presents a design methodology for using steel coupling beams that have a replaceable fuse. Laboratory test data were found to validate the methodology. A 2-story prototype building was designed according to the proposed methodology and results from nonlinear static and dynamic analyses indicate that the building performed according to the objectives of the presented design methodology. That is, (1) the midspan fuses are the primary energy-dissipating components; (2) the fuses develop their capacity before the embedded beams reach their expected shear or elastic flexural capacities; (3) the wall piers experience little or no damage under design ground motions; (4) the wall piers maintain their integrity for maximum credible ground motions; and (5) residual deformations are small, permitting new fuses to be installed following design-level ground motions.