Abstract
A series of structural vulnerability analyses are conducted on a reinforced cold-formed steel (RCFS) shear wall system and a traditional cold-formed steel (CFS) shear wall system subjected to earthquake hazard based on forms in order to investigate their failure mechanisms. The RCFS shear wall adopts rigid beam-column joints and continuous concrete-filled CFS tube end studs rather than coupled-C section end studs that are used in traditional CFS shear walls, to achieve the rigid connections in both beam-column joints and column bases. The results show that: the RCFS and traditional CFS shear wall systems both exhibit the maximum vulnerability index associated with the failure mode in the first story. Therefore, the first story is likely to be a weakness of the CFS shear wall system. Once the wall is damaged, the traditional CFS shear wall system would collapse because the shear wall is the only lateral-resisting component. However, the collapse resistance of the RCFS shear wall system is effectively enhanced by the second defense, which is provided by a framework integrated by rigid beam-column joints and fixed column bases. The predicted collapse mode with maximum vulnerability index that was obtained by structural vulnerability analysis agrees well with the experimental result, and the structural vulnerability method is thereby verified to be reasonable to identify the weaknesses of framed structures and predict their collapse modes. Additionally, the quantitative vulnerability index indicates that the RCFS shear wall system exhibits better robustness compared to the traditional one. Furthermore, the “strong frame weak wallboard” and the “strong column weak beam” are proposed in this study as conceptional designations for the RCFS shear wall systems.
Highlights
In recent decades, cold-formed steel (CFS) shear wall systems are considered to be one of the most feasible approaches for constructing residential and commercial low-rise and mid-rise buildings because this system has numerous benefits such as environmental-friendly and recyclable materials, lightweightness, high performance, cost-effectiveness, dimensional modularity and stability, and convenience for construction
The reason for the safety is that the collapse resistance of the whole structure can be effectively enhanced due to the second defense line in addition to the sheathings, structure can be effectively enhanced due to the second defense line in addition to the sheathings, which is provided by the framework integrated by beams and end studs under rigid connection which is provided by the framework integrated by beams and end studs under rigid connection conditions
reinforced cold-formed steel (RCFS) shear wall systems may have a total collapse mode caused by end stud failure, which is disadvantageous to the collapse resistance of the structure
Summary
Cold-formed steel (CFS) shear wall systems are considered to be one of the most feasible approaches for constructing residential and commercial low-rise and mid-rise buildings because this system has numerous benefits such as environmental-friendly and recyclable materials, lightweightness, high performance, cost-effectiveness, dimensional modularity and stability, and convenience for construction. Ye [13,17] proposed a reinforced cold-formed steel (RCFS) shear wall system, in which a concrete-filled CFS tube was used as an end stud to prevent local buckling, and a reinforced block beam-column joint was presented in order to achieve a rigid connection. Shaking table tests were performed on low-rise CFS shear walls [23,24,25]; the test results revealed that sheathing failure along with the end studs losing their axial load-bearing capacities in succession were the typical failure modes of those structures. The failure mechanism investigations were performed mainly by cyclic testing of CFS shear walls and shaking table test of CFS structures, and macro-indexes (such as inter-story drift and force) were used to reveal the failure process by analyzing the typical failure modes of the structures.
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