In the realm of structural engineering, a profound understanding of the behavior of reinforced concrete (RC) columns under various loading conditions is paramount for ensuring the safety and stability of structures. The study by Basyaruddin et al., titled "Cyclic Behavior of Steel Tube Confined Circular RC Columns under High Axial Load," presents a significant contribution to the analysis of the cyclic response of these columns, particularly those under high axial loads. This study's findings will undoubtedly enlighten and inform structural engineers, researchers, and professionals in the field of civil engineering.

Concrete filled steel tubes on-site.

This study, published on July 31, 2024, in the Journal of Structural Engineering by ASCE, investigates the cyclic responses of steel tube-confined RC columns. Eleven column specimens were tested under lateral displacement reversals and axial loads of either 0.3𝐴𝑔𝑓𝑐⁢𝑚, 𝑐 or 0.5𝐴𝑔𝑓𝑐⁢𝑚, 𝑐, where 𝐴𝑔 represents the concrete cross-section area and 𝑓𝑐⁢𝑚, 𝑐 is the tested concrete strength. Three specimens represented conventional RC columns; the remaining eight were steel tube-confined circular RC columns.

The critical test parameters included:

- Amount of longitudinal reinforcement.

- Axial load level.

- Continuity of the confining steel tube.

- Clear cover of the longitudinal reinforcement.

Test results showed that all steel tube-confined RC specimens sustained the target axial load and maximum lateral strength up to 10% drift ratio. Additionally, a simple strength model was proposed to reasonably estimate the maximum strength of the steel tube-confined RC columns.

A critical aspect of the study was the analysis of flexural rigidity, represented by the ratio (𝐸⁢𝐼)𝑡⁢𝑒⁢𝑠⁢𝑡/𝐸𝑐⁢𝑚, 𝑐⁢𝐼𝑔. For conventional RC specimens and those confined by a continuous steel tube, this ratio ranged between 0.6 and 0.8. However, specimens confined by a cut-off steel tube showed a significantly lower ratio, between 0.3 and 0.6.

This study significantly enhances the understanding of the cyclic behavior of steel tube-confined RC columns under high axial load. Moreover, it provides a practical model for estimating their maximum strength, which can be directly applied to structural design in civil engineering. The findings of this study are not just informative, but also highly relevant and applicable to the work of structural engineers, researchers, and professionals in the field.

Reference

Cyclic Behavior of Steel Tube-Confined Circular RC Columns under High Axial Load | Journal of Structural Engineering | Vol 150, No 10 (ascelibrary.org)