Behavior and design of eccentrically compressed
\nhybrid steel and GFRP reinforced concrete
\ncolumns at elevated temperature
\nHaitham Al-Thairy1,2
\n1Civil Engineering Department, College of
\nEngineering, University of Al-Qadisiyah,
\nAl-Diwaniyah, Iraq
\n2College of Engineering, University of
\nWarith Al-Anbiyaa, Karbala, Iraq
\nCorrespondence
\nHaitham Al-Thairy, Civil Engineering
\nDepartment, College of Engineering,
\nUniversity of Al-Qadisiyah,
\nAl-Diwaniyah, Iraq.
\nEmail: haitham.althairy@qu.edu.iq
\nAbstract
\nThis study presents analytical model for the analysis of hybrid (steel and fiber
\nreinforced polymers (FRP)) reinforced concrete (RC) columns at elevated temperature
\nunder eccentric compressive loads. The bending moment resistance
\nof the (RC) columns at elevated temperature is formulated based on force
\nequilibrium and strain compatibility of the concrete column section under
\ncombined bending moment and axial force. Deterioration the mechanical
\nproperties of concrete, steel, and FRP bars due to the rise of temperature has
\nbeen taken into account using equations proposed by previous studies. Validating
\nthe suggested model was carried out by comparing the analytical results
\nwith corresponding experimental and numerical results in terms of axial loadlateral
\ndisplacement relationships, axial load-bending resistance interaction
\ndiagrams, and failure modes. Validation results have shown the accuracy of
\nthe suggested analytical model. A parametric study has also been conducted
\nusing the proposed analytical model to investigate the effect of some parameters
\non the axial load-bending resistance interaction diagrams of hybrid steel
\nand FRP-RC columns under elevated temperature. These parameters include
\nthe effect of higher temperature values, the effect of reinforcement material,
\nand the effect of reinforcement configuration. Parametric study results have
\nrevealed some interesting conclusions that may be implemented in the design
\nof hybrid RC columns at fire.
\nK E YWO R D S
\nelevated temperature, FRP bars, hybrid reinforcement, interaction diagrams, RC columns
\n1 | INTRODUCTION
\n1.1 | Review of literature
\nOver the past two decades, using fiber reinforced polymers
\n(FRP) bars in reinforced concrete industries has
\nhighly increased due to the attractive mechanical characteristics
\nof FRP bars compared to the ordinary steel bars
\nsuch as the high strength-to-weight ratio and the
\ncorrosion resistance. Therefore, a demand of the FRP
\nbars in design and construction of concrete structures has
\nbeen growing nowadays, particularly at harsh environments
\nsuch as marine structures, large span bridges, and
\nbasement parking garages. However, FRP bars implicate
\nspecific drawbacks which could limit the scope of implementation
\nin concrete design such as low modulus of
\nelasticity and low fire endurance compared to that of the
\nconventional steel bars. Consequently, using hybrid
\nReceived: 1 September 2023 Revised: 1 February 2024 Accepted: 4 April 2024
\nDOI: 10.1002\/suco.202300734
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