This study proposes innovative multi-spiral confinement for reinforced concrete columns. The proposed confinement schemes include of seven-spiral for oblong columns, six-spiral and eleven-spiral for rectangular columns. Three series of test were conducted to investigate the cyclic performance of columns with proposed innovative multi-spiral confinement. The shear and flexural behavior of the multi-spiral columns with 1/3 scale were examined in Phase I and Phase II, respectively. The seismic performance and construction cost of a large-scale rectangular column with six-spiral reinforcement was investigated in Phase III to compare with those of a corresponding rectangular column with conventional tied reinforcement. Test results showed that the columns with proposed innovative multi-spiral reinforcement exhibited better performance in both shear and flexure than the corresponding tied columns, even with less amount of transverse reinforcement. In addition, based on automation technology, multi-spiral columns have lower construction cost and construction time compared with tied columns. Multi-spiral confinement worked very effectively without any separation among the spirals. Multi-spiral columns with H-shaped as longitudinal reinforcement showed significantly higher ductility and energy dissipation, but lower overstrength than columns with deformed bars.
The discrete computation shear strength (DCSS) models were proposed to calculate shear strength provided by multi-spiral transverse reinforcement. Examination of the difference between the DCSS models and integral averaging method shows that the error of the later increases with increasing ratio of spacing to diameter of spirals. The limiting values of spacing to diameter ratios were proposed to control the error of integral averaging method to be equal or less than 10%. Plot of modification factors were proposed to be used with the simplification calculation when the spacing to diameter ratio is large.
Moreover, in term of shear failure point prediction, both Caltrans SDC and Sezen models are good to provide close estimates of experimental behavior. To predict the maximum probable moment strengths, only the Caltrans SDC method produced conservative result for all columns tested.

This study proposes innovative multi-spiral confinement for reinforced concrete columns. The proposed confinement schemes include of seven-spiral for oblong columns, six-spiral and eleven-spiral for rectangular columns. Three series of test were conducted to investigate the cyclic performance of columns with proposed innovative multi-spiral confinement. The shear and flexural behavior of the multi-spiral columns with 1/3 scale were examined in Phase I and Phase II, respectively. The seismic performance and construction cost of a large-scale rectangular column with six-spiral reinforcement was investigated in Phase III to compare with those of a corresponding rectangular column with conventional tied reinforcement. Test results showed that the columns with proposed innovative multi-spiral reinforcement exhibited better performance in both shear and flexure than the corresponding tied columns, even with less amount of transverse reinforcement. In addition, based on automation technology, multi-spiral columns have lower construction cost and construction time compared with tied columns. Multi-spiral confinement worked very effectively without any separation among the spirals. Multi-spiral columns with H-shaped as longitudinal reinforcement showed significantly higher ductility and energy dissipation, but lower overstrength than columns with deformed bars.
The discrete computation shear strength (DCSS) models were proposed to calculate shear strength provided by multi-spiral transverse reinforcement. Examination of the difference between the DCSS models and integral averaging method shows that the error of the later increases with increasing ratio of spacing to diameter of spirals. The limiting values of spacing to diameter ratios were proposed to control the error of integral averaging method to be equal or less than 10%. Plot of modification factors were proposed to be used with the simplification calculation when the spacing to diameter ratio is large.
Moreover, in term of shear failure point prediction, both Caltrans SDC and Sezen models are good to provide close estimates of experimental behavior. To predict the maximum probable moment strengths, only the Caltrans SDC method produced conservative result for all columns tested.

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