IIARD International Institute of Academic Research and Development

International Journal of Engineering and Modern Technology (IJEMT )

E-ISSN 2504-8848
P-ISSN 2695-2149
VOL. 11 NO. 5 2025
DOI: 10.56201/ijemt.vol.11.no5.2025.pg218.227

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Experimental Investigation of the Structural Performance of Circular Reinforced Concrete Columns Under Concentric Loading at Varying Slenderness Ratios

Damini Righteous Gilbert, Orumu ST, and John AT

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Abstract

This study experimentally investigates the structural performance of circular reinforced concrete (RC) columns subjected to concentric axial loading, focusing on the effect of varying slenderness ratios. A total of 54 columns were cast using three concrete grades M15, M20, and M25 and tested at six different length-to-diameter (L/D) ratios: 1, 3, 5, 7, 9, and 10. All columns were reinforced with 4Y8 longitudinal bars and tested under uniform loading conditions to evaluate axial load capacity, failure modes, and deformation characteristics. Results showed a significant reduction in axial load capacity with increasing slenderness. For M25-grade concrete, columns with an L/D ratio of 1 achieved a maximum axial load of 287.5?kN, while those with an L/D of 10 carried only 116.7?kN a 59.4% decrease. Similarly, M20 columns dropped from 266.7?kN at L/D 1 to 112.5?kN at L/D 10, reflecting a 57.8% decrease, and M15 columns decreased from 237.5?kN to 95.8?kN, a 59.7% reduction. This confirms that slender columns are more prone to buckling and instability under axial compression. Conversely, concrete grade had a positive influence on capacity. At constant L/D ratios, increasing concrete strength from M15 to M25 led to axial load capacity increases ranging from 15% to 26%, depending on the slenderness. For example, at L/D 5, the load capacity improved by 22.2% when upgrading from M15 (181.7?kN) to M25 (225.0?kN). Failure patterns further validated these results: stocky columns (L/D ? 3) exhibited crushing and ductile behavior, while slender columns (L/D ? 7) failed through buckling with minimal warning. The findings emphasize the critical role of slenderness and concrete grade in axial performance, providing practical insights for structural design and reinforcing the need for code provisions that accurately reflect slenderness effects in circular RC columns.

keywords:

Circular, columns, axial loading, slenderness ratio, structural performance

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