Investigation of the structural performance of reinforced concrete long slender columns strengthened with stainless steel, galvanized steel, and aluminum sheets

Abstract

This study presents experimental and numerical investigations into the structural performance of long slender reinforced concrete columns strengthened with externally bonded stainless steel, galvanized steel, and aluminum sheets. Twelve full-scale columns (100 mm in diameter cross-section and 1000 mm height) were tested under monotonic axial compression loading to evaluate improvements in load-carrying capacity, ductility, and energy absorption. The specimens were divided into four groups: unstrengthened columns with varying internal stirrup spacings (150 mm, 120 mm, and 90 mm), and columns externally confined using stainless steel, galvanized steel, or aluminum sheets with different widths (55 mm, 83 mm, 100 mm) and spacings (110 mm, 166 mm, 200 mm), ensuring a consistent volumetric reinforcement ratio of approximately 0.5 %. Reducing stirrup spacing improved the axial behavior, increasing load capacity by up to 16 % and energy absorption by 93 % compared to the reference. Columns strengthened with stainless steel sheets achieved up to an 80 % increase in peak load and a 4.5-fold increase in energy absorption compared to unstrengthened columns. Aluminum sheets also showed substantial improvements, with up to a 55 % increase in strength and nearly a 3.8-fold increase in energy dissipation. In addition to higher capacity, the strengthened columns exhibited a distinct shift from brittle to ductile failure modes. In addition, a Finite Element (FE) modeling approach was developed using ABAQUS to simulate the tested specimens. The model was validated against experimental results and subsequently employed to perform a comprehensive parametric study. The FE model showed close agreement with experiments, with load ratios of 0.96–1.05. Parametric analysis revealed that full wrapping improved capacity by up to 28 %, while increasing stainless steel thickness to 0.3 mm enhanced axial resistance by 77 % before plateauing.