Effects of loading protocol on the cyclic response of woodframe shearwalls

Standard construction 2.4 mx 2.4 m woodframe shearwalls were tested using different loading protocols. The CUREE-Caltech protocols, recently developed by Krawinkler in 2001, were compared with other, previously used protocols. The following protocols were considered in the study: monotonic, CUREE-Caltech standard (CUREE), CUREE-Caltech near-fault, sequential phased displacement (SPD), and international standards organization. Findings from the research indicate that loading sequence has a significant influence on shearwall performance. Protocols with a large number of cycles (SPD) tended to produce nail fatigue fractures, which were not nearly as prevalent in protocols with lower numbers of cycles (CUREE). The research clearly showed that the nail fatigue fractures were associated with a large energy demand related to the number of cycles, which resulted in a reduced ultimate strength and deformation capacity. The initial stiffness of the specimens was relatively unaffected by the loading protocol used; however, there was significant variation in the stiffness values obtained depending on the stiffness definition used.