Studies on the Provisions of Confining Reinforcement for High-strength Concrete Column

It is general knowledge that the design of earthquake-resistant structures for high-strength concrete columns requires confining-reinforcement with a relatively high volumetric ratio to ensure the ductility of the structure. This implies that the mechanical behavior of high-strength concrete differs significantly from the behavior of normal-strength concrete. However, the provisions on the minimum volumetric ratio of confining-reinforcement contained in the Indonesian Concrete Code (SNI 2847-2013) is essentially derived from the test results for normal-strength concrete. This paper studies the confining-reinforcement provisions used in several standards, i.e., SNI 2847-2013, ACI-2011, NZS-2006 and CSA-2004, to determine the ductility of the concrete columns. The case study is based on the analysis of the cross-section of high-strength concrete columns, the parameters that affect the strength, and by evaluating the value of the column's cross-section curvature ductility. The study results showed that the equation for confining-reinforcement adopted in the SNI 2847-2013 is very conservative compared to other codes when applied to low axial load levels (≤0.2), but is relatively less conservative if the axial load level is greater than 0.3.