Circular High-Strength Concrete Columns under Concentric Compression

Circular columns with concrete strengths in the range of 60 MPa to 124 MPa were tested under concentric compression. The columns were confined with different volumetric ratios, grades, and spacings of circular reinforcement. Tests included both poorly confined and well-confined columns. The results provided insight into the strength and deformability of circular high-strength concrete (HSC) columns and were used to generate design information for confinement of these columns. The test data indicate that HSC columns exhibit extremely brittle behavior unless confined by lateral reinforcement. The columns require higher confinement pressure than those with normal strength concrete. The additional pressure required can by provided by increasing the volumetric ratio and/or the grade of transverse reinforcement. The p(sub s)f (sub yt)/f'(sub c) ratio was found to be a suitable design parameter for confinement of circular high-strength concrete columns up to a concrete strength level of 124 MPa. Transverse spiral reinforcement of up to 1,000 MPa was observed to be effective in confining concrete. The results further indicated that circular hoops are as effective as circular spirals when the hoops are prevented from opening under lateral expansion.