Circular high-strength concrete columns under concentric compression

Circular columns with concrete strengths in the range of 60 to 124 MPa (8.7 to 18.0 ksi) were tested under concentric compression. The columns were co nfined with different volumetric ratios, grades, and spacings of circular r einforcement. Tests included both poorly confined and well-confined columns . The results provided insight into the strength and deformability of circu lar high-strength concrete (HSC) columns and were used to generate design i nformation 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 confin ement pressure than those with normal strength concrete. The additional pre ssure required can be provided by increasing the volumetric ratio and/or th e grade of transverse reinforcement. The p(s)f(yt)/f(c)' ratio was found to be a suitable design parameter for confinement of circular high-strength c oncrete columns, up to a concrete strength level of 124 MPa (18.0 ksi). Tra nsverse spiral reinforcement of up to 1000 MPa (145 ksi) was observed to be effective in confining concrete. The results further indicated that circul ar hoops are as effective as circular spirals when the hoops are prevented from opening under lateral expansion.