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Deflection of Concrete Beams Prestressed by CFRP Bars
Background/Objectives: Carbon Fiber Reinforced Polymer (CFRP) is preferred due to its non-corrosive and high strength.The serviceability behavior of prestressed concrete beam changes due to the less stiffness and non-ductililty of CFRP.Methods/Statistical Analysis: An experimental investigation is carried out to study the deflection and crack width behavior of prestressed concrete beam using CFRP bars. Four rectangular beam specimens were considered forcasting, stressing by varying degree of prestressing of 35 to 70 % and tested. The moment curvature behaviors of experimental results were compared with various researchers’ recommendations. Findings: The deflection of CFRP prestressed concrete beam is by deformability of member. The deformability behavior depends on residual strain on CFRP bar after decompression of prestressing strain. The shift of moment of inertia and neutral axis of member are changing with respect to deformability behavior of member. The rate of shift of moment of inertia after first crack on member is faster for the low deformability member due to less residual strain only available in CFRP bar to deform which leads to faster rate of increase in deflection.The shift of neutral axis is due to crack on concrete leads to increase in prestressing moment of resistance. The rate of shift of neutral axis is slower for low deformability beam due to high degree of prestressing of member result in high tension stiffening at bottom of member. Reference recommendation of softening the moment of inertia by comparing modulus of elasticity of CFRP with steel is not realistic because the steel deform by ductility wherein FRP bar by deformability. Applications/Improvements: Proposed new deflection model is based on deformability behavior of CFRP prestressed concrete member, hence more number of experimental and numerical studies required validate the proposed model.
Deflection, Deformability, Moment of Inertia, Neutral Axis, Prestressing, Serviceability.
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