PERFORMANCE BASED. DESIGN OF CONFINEMENT REINFORCEMENT FOR CIRCULAR RCC COLUMNS

Abstract

Despite these research efforts, how to design and detail confinement reinforcement remains a somewhat puzzling issue. The confinement requirements of the current ACI Code (ACI 318-02) and NZS code (NZS 3101-1995) are still based on the philosophy that the axial load carrying capacity of a column should be maintained after spalling of the cover concrete. In practice, however, the confinement is required to produce ductile behavior of the columns subjected to a combination of forces. Hence a rational design approach should relate the ductile behavior of a column to the confinement requirements, with due considerations given- to those factors that have significant effects on column ductility. In this dissertation, design equations given by ACI 318-02, NZS 3101:1995 and IS 13920:1993 for circular columns are studied with respect factors affecting the amount of confinement reinforcement and equations are proposed for amount of confining reinforcement for potential plastic hinge region of columns considering the factor curvature ductility which is not included in either of the equations. These design equations are given for normal strength as well as high strength concrete for normal to high strength transverse steel for circular columns: Ductility achieved is obtained from the moment curvature analysis of various columns using XTRACT software. Wide range of parameters which affects the amount of confining reinforcement for circular columns such as axial load level, strength of confining steel, percentage of longitudinal steel, curvature ductility, Ag/Ac ratio, compressive strength of concrete normal to high strength '(up to I OOMPa) are considered. Proposed equations are compared with existing equation for quantities of confining reinforcement.