Flexural Behavior of Reinforced Concrete Columns with Supplementary V-Shaped Ties

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Title: Flexural Behavior of Reinforced Concrete Columns with Supplementary V-Shaped Ties

Author(s): Keun-Hyeok Yang, Min-Kyoung Kwak, and Jae-Il Sim

Publication: Structural Journal

Volume: 114

Issue: 05

Appears on pages(s): 1177-1188

Keywords: columns; crossties; flexural ductility; V-ties

Date: 9/1/2017

Abstract:
This study examined the flexural behavior of reinforced concrete (RC) columns with V-shaped ties as an alternative to the conventional crossties specified in ACI 318-14. Ten columns were tested to failure under constant axial loads and reversed cyclic lateral loads with the aim of exploring the potential for practical application of the proposed V-tie arrangement for enhancing column ductility. The parameters investigated were the axial load level, the compressive strength of concrete, and the column section size. The backbone curves of columns obtained from the reversed lateral load-displacement relationship were compared with predictions derived using a nonlinear two-dimensional (2-D) lamina method. Test results ascertained that the conventional crossties with a 90-degree hook are unfavorable to the enhancement of the flexural ductility of columns and prevention of the premature buckling of longitudinal bars, particularly under high axial load levels, owing to the opening of their 90-degree hooks. Meanwhile, the extraction of V-tie legs from the core concrete was not observed until the columns failed. As a result, higher displacement ductility ratio and work damage indicator were obtained for V-tie columns than for crosstie columns, indicating that the superiority of the V-ties to the conventional crossties in enhancing the flexural ductility of columns becomes more pronounced as the axial load level and concrete compressive strength increase. The flexural behavior of RC columns with V-ties could be accurately evaluated using the proposed 2-D lamina approach. However, the slope at the descending branch of the lateral load-displacement curve of the crosstie columns was lower than the corresponding prediction results owing to the opening of the 90-degree hooks.