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Coupled core walls utilizing steel coupling beams are effective structural systems for resisting earthquake demands that a building might experience in a seismically active area. Superior strength, stiffness, and hysteretic behavior are all advantages these systems provide. Research conducted at the University of Cincinnati has led to the development of a new, innovative type of steel coupling beam with a replaceable, weak-link section at the center of the coupling beam clear span. Inducing a weak-link, called a steel fuse, in a coupling beam provides a means by which damage may be localized and controlled, providing advantages such as post-event repairability and preserved integrity of reinforced concrete walls and embedded beam sections, which are costly to repair.Presented herein is a detailed design procedure for a Steel Fuse Coupling Beam (SFCB), including the careful detailing concerns necessary to achieve the performance desired, the design and analysis of a twenty story coupled core wall system utilizing SFCBs, and an experimental observation of a SFCB subjected to cyclic loads to simulate earthquake forces on such a system. Both linear-elastic and nonlinear analyses were completed on the twenty story prototype structure in order to provide a global picture of the performance of this new type of coupling beam system as it relates to a building structure. The experimental evaluation of a SFCB consisted of a single, half-scale subassembly consisting of two wall piers and a SFCB. Two steel fuses were fabricated for the coupling beam. As part of the experimental program, the concept of replacing the weak-link section, i.e., the fuse was demonstrated through the testing of the first fuse installed in the assembly, and then the removal and installation of the second, identical fuse. The second fuse assembly was tested using an identical loading sequence as the first fuse, and then to demands surpassing the first test. Comparisons have been made for the two SFCB assemblies, evaluating the integrity of the repaired system in terms of overall ductility and energy dissipation capacities.Prototype structure modeling provides a means to assess the condition of coupled walls using SFCBs, particularly with post-event condition in mind. The results from a push-over analysis are used to examine sequence of plastic hinge formation in SFCBs as well as structural integrities for embedded beams and reinforced concrete wall piers. A parametric study is also included, looking at the scenario of the same prototype structure model designed with conventional steel coupling beams (SCBs) in place of SFCBs. Comparisons are drawn as to building economy and performance, and conclusions are made as to the overall effectiveness of steel fuse coupling beams with respect to steel coupling beams. Overall, the adequacy of the SFCB methodology is presented and discussed.It is concluded that the replacement methodology and protection of permanent elements within steel fuse coupling beams is achievable, and that the performance of structures utilizing SFCBs is desirable for applications to earthquake engineering. |
