Behavior of Square RC Columns Confined with Interlocking Square Spiral Under Axial Compressive Loading

– Failures in building structures due to the earthquake occurred more frequently in columns than in beams, mainly when they have not been designed to comply with the strong column-weak beam concept, even though the columns have been designed to have enough ductility. However, the lack of confinement in columns plays an important role in the collapse of the columns. Up to the present, many design engineers have used square columns with traditional confinement in their designs. There has been no significant innovation in the confinement system in the past few decades. The only research known to the author has been an investigation of columns with circular spiral confinement. This paper presents a new confinement system for square columns with square spirals and interlocking combinations, which performs better than the traditional confinement. This type of confinement is adaptable to the column size and shape, efficient in manufacture and installation, and free from seismic hook congestion during concreting. The study aims to obtain the behavior of square columns with square spiral confinement with or without interlocking by investigating their stress-strain relationships compared with traditional confinement. Then the square column specimens have been tested under axial compression to failure in order to obtain the axial compressive behavior. From the test results, it can be concluded that the column specimen with square spiral and interlocking combination has indicated higher axial compressive strength and strain ductility rather than the traditionally confined column specimen.