Shear performance degradation of cold-formed steel shear walls sheathed with gypsum boards under multi-cycle reversed loading

摘要

Full-scale cold-formed steel (CFS) shear walls were tested. The effect of the fasteners? accumulative damage on the performance degradation of the walls was investigated. The differences in the walls with different amounts of stiffness under different loading processes were explored. The results show that, (1) The stiffness of C-section chord studs is low. The damage to CFS shear walls was serious. Under the longer loading process, the wall finally lost the ?diaphragm effect? between the steel frame and sheathings. The walls with concrete-filled steel-tubular struts bolted at both ends (RCFS shear walls) have larger stiffness. There was no obvious difference in the damage to RCFS shear walls under the different loading processes. (2) The damage level of a wall under horizontal load should be divided into five stages, including neglectable damage (I), repairable mild damage (II), moderate damage (III), irreparable severe damage (IV) and failure (V); under the same conditions, the longer the loading process is, the earlier a wall will enter the subsequent damage stage. Compared with the CFS shear walls, the RCFS shear walls had superior shear performance under long-term horizontal load. Considering the strength degradation and stiffness degradation at the same loading level, an improved piecewise function hysteresis model suitable for RCFS shear walls was established and compared with the test results. The results indicate that the proposed model can fully reflect the performance degradation of RCFS shear walls under long-term horizontal load. The relative errors between the calculated results and the test results are within 15%.