Abstract
This study was performed with the objective of improving ealthquake-resistant behaviors of reinforced concrete columns. Columns often develop shear failure, bond-split failure, or flexural compression failure without showing sufficient ductility after flexural yielding. In this study, it was tried to make clear experimentally the relationship between ductility and structural details such as the arrangement of main bars and axial load levels. The experiment covered the range of 1 to 2 in shear span ratio, and 0.34〜1.44 percent in tensile reinforcement ratio. From the test results of nineteen columns subjected to bending moment, shear force and axial force, concluding remarks are induced as follows : i) To provide many thin main bars and to envelope them with hoops is not effective for the prevention of bondsplit failure, if tensile reinforcement ratio is as high as about 1 percent. On the contrary to provide thick main bars at the corner of welded or rectangular spiral hoops improves the behaviors a little for the prevention of bond-split failure. ii) To restrain all main bars with either welded hoops or rectangular spiral hoops and supplementary ties together is effective especially for the prevention of the bond-split failure and improve the ductility. iii) In circular columns with circular spiral hoops, even when axial stress coefficient N/bDF_c is in the order of 1/2, 1/3, flexural compression failure is prevented and columns showed very large ductility. Circular spiral hoops are effective for the prevention of bond-split failure too.
