The Effects of Transverse Reinforcement on the Strength and Deformability of Reinforced Concrete Elements

Post-earthquake examinations of reinforced concrete structures often show structural damage resulting from bond and shear failures. Such failures typically occur in reinforced concrete elements with details known to cause problems, such as widely spaced transverse reinforcement and/or lap splices located in regions of flexural yielding. These details are common in older reinforced concrete buildings (built before 1970) that have reinforced concrete columns with longitudinal reinforcement spliced just above the floor level, and transverse reinforcement spaced at a distance of d/2 or longer. This investigation focused on means to increase the deformability of existing reinforced concrete elements susceptible to bond and shear failures during a seismic event or other applications requiring toughness. The effects of confinement provided by epoxied anchors, spiral transverse reinforcement, and post-tensioned external clamps were investigated. Emphasis was placed on producing a strengthening device that can be sized, fabricated, and installed with ease because most of the existing strengthening techniques require specialized labor, tools, and materials. The observations collected support the idea that active confinement provided by post-installed and post-tensioned transverse reinforcement was the most effective method to improve structural deformability among the methods studied and within the ranges considered.