Shear-transfer mechanism and capacity mobilization of high-strength spiral-confined RC wall panels under shear loading

Reinforced concrete (RC) wall panels are important lateral-load-resisting components, yet the shear-transfer mechanism of panels reinforced with high-strength spiral reinforcement remains insufficiently understood. In this study, eight RC wall panels with a shear-span ratio of 1.0 were tested under monotonic loading using a four-corner loading system designed to generate a shear-dominated stress state. The effects of spiral reinforcement spacing, reinforcement configuration, and lap connection on cracking, shear deformation, reinforcement strain, and internal force transfer were investigated. Diagonal cracking developed along the tension diagonal, accompanied by a principal compression field along the opposite diagonal. Reducing the spacing of high-strength spiral distributed reinforcement improved post-cracking stiffness and restrained shear deformation. At test termination, most reinforcement had not yielded and no evident crushing of the diagonal concrete compression strut was observed. Because all specimens were ultimately controlled by premature failure of the corner connection components, the measured maximum force was defined as the test peak shear force rather than the intrinsic ultimate wall-panel shear capacity. Based on the observed force-transfer mechanism, a spiral-constrained strut-and-tie model (SC-STM) was developed to estimate the theoretical potential shear capacity and quantify its degree of mobilization before connection-controlled termination.