Shear behavior of oblong bridge columns with innovative seven-spiral transverse reinforcement

An innovative seven-spiral transverse reinforcement is proposed for oblong reinforced concrete bridge columns. Compared to conventional single-spiral or two-spiral transverse reinforcement, the proposed scheme reduces the size of the spirals and hence improves the constructibility of spirals for large bridge columns. Four seven-spiral columns were tested under high shear stress to assess their performance. Comparable conventional tied and two-spiral columns were also tested. Test results showed that spirals in the proposed seven-spiral columns remained interlocked. With less transverse reinforcement, the seven-spiral columns achieved similar or better shear performance compared to the tied columns. The seven-spiral column exhibited the highest effective shear coefficient, followed by the two-spiral column and the tied column. Comparison of shear-strength predictions with the test results shows that the ACI 318 model generally provides conservative estimates, and the Caltrans SDC and Sezen models provide reasonable estimates of experimental behavior in terms of failure point prediction.