IIARD International Institute of Academic Research and Development

RESEARCH JOURNAL OF PURE SCIENCE AND TECHNOLOGY (RJPST )

E-ISSN 2579-0536
P-ISSN 2695-2696
VOL. 8 NO. 5 2025
DOI: 10.56201/rjpst.vol.8.no5.2025.pg77.84

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Experimental Study on the Influence of Length-to-Depth Ratio on the Axial Load Capacity of Reinforced Concrete Square Columns at Varying Concrete Grades

Orumu S.T., Damini Righteous Gilbert, and John A.T.

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Abstract

This experimental study investigates the influence of length-to-depth (L/D) ratio on the axial load capacity and failure behavior of reinforced concrete (RC) square columns constructed with varying concrete grades (M15, M20, and M25). A total of 54 column specimens were tested under axial compression, each with a constant cross-section of 100 mm × 100 mm, a fixed reinforcement ratio of 2.8%, and varying L/D ratios ranging from 1 to 10. The results revealed a strong inverse relationship between L/D ratio and axial load capacity across all concrete grades. Columns with lower L/D ratios exhibited significantly higher axial load capacities due to their reduced susceptibility to buckling, with specimens at L/D = 1 demonstrating up to a 293% increase in axial load capacity compared to those at L/D = 10. Additionally, the concrete grade had a pronounced effect on axial performance: at an L/D ratio of 1, M25-grade columns (RC-A1-25) achieved axial loads 10.2% and 26.4% higher than M20 (RC-A2-20) and M15 (RC-A3-15) grades, respectively. At the slenderest ratio (L/D = 10), M25 columns maintained capacities 11.1% and 22.8% greater than M20 and M15 columns. Failure modes were strongly influenced by slenderness; slender columns (L/D ? 9) predominantly failed by buckling, while shorter columns (L/D ? 7) exhibited crushing failure. These findings highlight the critical importance of both L/D ratio and concrete strength in optimizing the structural design and axial load capacity of reinforced concrete columns.

keywords:

Concrete Grade, Columns, Length-to-Depth Ratio, Failure Modes, Axial load

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