Energy based methodology for ductile design of concrete columns

Potential plastic hinge zones in confined concrete columns require that sufficient transverse reinforcement be provided to avert undesirable. failure modes and to ensure dependable inelastic (ductile) behavior in earthquakes. Conventional code-based approaches for detailing confining reinforcement are founded on the premise of preserving axial load before and after spalling of the cover concrete. Such formulations account for neither the cyclic actions nor the duration effects of ground motions. This paper derives the amount of transverse reinforcement necessary so that hoop fracture and fatigue fracture of the longitudinal bars coincide for critical earthquake motions. An energy-based approach coupled with notions of low cycle fatigue are used for this purpose.