Abstract
The objective of this study is to know how failures of columns develope or how ductility of columns is kept on the basis of experimental data. The various kinds of failure such as the failures of the plastic hinge at the ends of column or the failures at the center of column was presumed by the truss mechanism which varied with the progress of failure. Shear transfer mechanism was also studied by this mechanism. Columns which showed large ductilities fainally failed in the plastic hinges at the ends of the column. Those columns had not only sufficient shear reinforcement at the hinges, but also sufficient shear strength at the center parts of the columns. In such a column the strains of web reinforcements at ultimate condition showed large valure at the ends of the column, while the strains became smaller as nearer the center of the column. When the strains of a part of web reinforcements at the plastic hinge region of any columns reached yielding strain, load carrying capacity of column began to decrease until breakage. Average value of maximum strain of web reinforcements in the plastic hinge region of the column which showed excellent ductility, was about sixty percent of yield strain. It was recognized that shear force resisted by web reinforcements in plastic hinge region increased in proportion to the increase of deflection of the column. In addition to above items, transition of strain distribution and average bond stress distribution of main bars were also examined.
