Cyclic Shear and Axial Strength of Lightly-Confined Concrete Columns

Before the introduction of special requirements in the 1970s, reinforced concrete building frames constructed in zones of high seismicity in the US had details and proportions similar to frames designed solely for gravity loads. Columns generally were not designed to have strengths exceeding beam strengths, so column failure mechanisms often prevail. Relatively wide spacing of transverse reinforcement was common, such that column failures may involve some form of shear or flexure-shear failure, in some cases followed by loss of axial load capacity. This study examines laboratory behavior of columns with light transverse reinforcement and proposes models for shear strength and subsequent axial load failure that may be suitable for evaluation of existing building frames.