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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.

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 GradeColumnsLength-to-Depth RatioFailure ModesAxial load

References

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