Axial Compression Performance of Reinforced Concrete Short Columns with Supplementary V-Shaped Ties


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Title: Axial Compression Performance of Reinforced Concrete Short Columns with Supplementary V-Shaped Ties

Author(s): Keun-Hyeok Yang and Won-Woo Kim

Publication: Structural Journal

Volume: 113

Issue: 6

Appears on pages(s): 1347-1356

Keywords: axial load; columns; confined concrete; crosstie; ductility ratio; supplementary transverse reinforcement; V-tie

Date: 11/1/2016

This paper presents a relatively simple V-shaped tie arrangement approach as an alternative to the conventional crossties for seismic design of reinforced concrete (RC) columns. For easy and quick installation of the individual V-ties, a connector that assembles the V-tie onto a longitudinal bar was also devised. The mechanical contribution of the V-tie was characterized regarding the confining core concrete and preventing the premature buckling of the longitudinal reinforcement. To determine the minimum extension length of V-tie legs into the core concrete, an equivalent lateral force was derived based on the transverse displacement due to the buckling of longitudinal reinforcing bars. Fourteen columns were tested to failure under concentric axial load to investigate the performance and shortcomings of the proposed V-tie approach. Test results showed that a 90-degree hook of crossties was gradually opened beyond the ultimate strength of columns. In contrast, no V-ties were extracted from core concrete during the period of tests, even for high-strength concrete columns under a compressive strength of 105 MPa (15.2 ksi). As a result, higher ductility ratios were observed in V-tie columns than in crosstie columns. The stressstrain curves of confined concrete obtained from the V-tie columns agreed well with prediction model proposed by Kim et al., indicating that the developed V-tie arrangement effectively confines the core concrete. In summary, the V-ties possess significant potential to provide supplementary transverse reinforcement of RC columns.