Strength and Ductility of Concrete Confined by External Wrap

Unlike circular columns, jacketing of oblong or wall-type columns produces only marginal improvement in strength and ductility because of inadequate confinement and premature debonding of the wrap. Some possible ways to overcome this problem, at least partially, are to round the corners, to add a semi-circular segment at each of its shorter sides or to produce an elliptical shape enclosing the oblong columns. A total of 13 specimens of these cross sectional shapes were tested in direct compression to assess the enhancement afforded by external fiber wraps. It has been found that the modification of a rectangular section by including a semi-circular segment on each of its shorter sides or transforming the section to an ellipse before applying fiber wrap leads to a substantial improvement in strength as well as ductility. Of the two fibers used, the glass fiber composite proved to be more cost effective in terms of strength and ductility enhancement.