Bending and Buckling Behavior of Hollow-Core FRP-Concrete-Steel Columns


This article presents a numerical study on the behavior of hollow-core fiber-reinforced polymer-concrete-steel (HC-FCS) columns under combined axial compression and lateral loadings. The investigated HC-FCS columns consisted of an outer circular fiber-reinforced polymer (FRP) tube, an inner square steel tube, and a concrete wall between them. The HC-FCS column has several advantages over RC columns. The tubes act a stay-in-place formwork, providing continuous confinement and reinforcement. The concrete shell prevents the outward buckling of the steel tube, which improves the column strength. Three-dimensional (3D) numerical models were developed and validated against experimental results. The models subsequently were used to conduct a parametric finite-element (FE) study investigating the effects of the concrete wall thickness, steel tube width-to-thickness (B/ts ) ratio, confinement ratio, concrete strength, applied axial load level, and buckling instabilities on the behavior of the HC-FCS columns, with a particular emphasis on local buckling of the inner tube. This study revealed that the behavior of HC-FCS columns is complicated due to the interaction of the stiffness of the three different materials: concrete, steel, and FRP. In general, in the HC-FCS columns with square steel tubes, failure was triggered by local buckling of the steel tube followed by FRP rupture. The presence of the concrete wall restrained by the outer FRP and inner steel tubes significantly affected the steel tube buckling. Expressions were also developed to predict the local buckling stresses and strains of the square steel tube.


Civil, Architectural and Environmental Engineering

Keywords and Phrases

Beams and girders; Columns (structural); Composite structures; Elasticity; Fiber reinforced plastics; Optical fibers; Reinforced concrete; Reinforced plastics; Reinforcement; Structural design; Tubes (components); Tubular steel structures, Buckling behaviors; Buckling instabilities; Confinement ratio; Fiber reinforced polymers; Hollow core fiber; Parametric finite elements; Square steel tube; Three dimensional (3D) numerical models, Steel fibers

International Standard Serial Number (ISSN)

1084-0702; 1943-5592

Document Type

Article - Journal

Document Version


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© 2019 American Society of Civil Engineers (ASCE), All rights reserved.

Publication Date

01 Aug 2019