Design of confinement reinforcement for RC columns

摘要

Transverse reinforcements in columns in the form of hoops, cross-ties, or spirals play an important role in safeguarding the columns, especially when they are subjected to strong earthquakes or accidental lateral loads. They are required in any column-whether they are parts of a moment resistant frame or the gravity system in order for them to deform laterally and provide the required ductility. The current equations for confinement reinforcement in IS 13920 code do not provide consistent level of safety against deformation and damage associated with flexural yielding during earthquakes. Hence an equation for the design of confinement reinforcement for ductile earthquake resistant rectangular and circular columns is suggested for inclusion in the next revision of the code. These equations take into account the various parameters that affect the performance ofconfin ing reinforcemen t, such as effective confining pressure or ratio of concrete strength to tie strength, axial load level, unconfincd cover concrete thickness, longitudinal reinforcement and spacing, and curvature ductility factor. Some detailing of these reinforcements is also discussed.