82-1 7 th International Specialty Conference on Engineering Mechanics and Materials Growing with youth – Croître avec les jeunes Laval (Greater Montreal) June 12 - 15, 2019 FLEXURAL BEHAVIOR OF RECTANGULAR CONCRETE FILLED FRP TUBES (CFFT) BEAMS POST TENSIONNED WITH STEEL TENDONS Asmaa Abdeldaim Ahmed 1, 3 , Mohamed Hassan 1, 2, 4 , Radhouane Masmoudi 1, 5 , 1 Department of Civil and Building Engineering, University of Sherbrooke - Sherbrooke, QC, Canada 2 Department of Civil of Engineering, Helwan University, Cairo, Egypt 3 Asmaa.Abdeldaim.Ahmed@USherbrooke.ca 4 Mohamed.Hassan@USherbrooke.ca 5 Radhouane.Masmoudi@USherbrooke.ca Abstract: The growth in the demand for prestressed concrete (PC) in the construction industry has steadily increased with time due to the superior performance and economy offered by PC over conventional reinforced concrete (RC) in a large number of structural engineering applications. Introducing prestressing for the concept of concrete-filled fiber-reinforced polymer (FRP) tube (CFFT) can provide this system many unique advantages, which makes it a good alternative for innovative sustainable and high-performance structures. This paper reports the test results of an experimental investigation aimed at evaluating the effect of longitudinal prestressing on the flexural performance of rectangular CFFT beams. Three full-scale beams were constructed and tested under a four-point bending over a span of 3.00 m. Of the three, two were reinforced CFFT beams with and without prestressing strands and one conventional prestressed (PRC) beam for comparison. All beams had identical cross-sectional of 305×406 mm 2 . The test results confirm the feasibility of prestressing for rectangular CFFT as flexural members. Prestressed rectangular CFFT beam show excellent load- deflection behaviour with high inelastic deformation and ultimate capacity compared to their counterparts CFFT with no prestressing and PRC beams. Prestressing could enhance the confinement effect of the concrete core under bending, which, in turn, improves the prestressed CFFT beam performance in deflection, strength, stiffness and ductility. The promising results can provide impetus for constructing prestressed rectangular CFFT under bending and constitute a step forward towards sustainable and high-performance hybrid structural elements. 1 INTRODUCTION Constructed infrastructure is aging with time and deteriorated due to a number of attributes such as corrosion, moisture, and chemical incompatibility. Thereby, the longevity of structural members is reduced. Corrosion damage is recognized as a crucial factor affecting the performance of concrete structures and corresponding consequences are significant. Although concrete cover retards the ingress of harmful matters into the structure, the occurrence of corrosion is inevitable in most reinforced or prestressed concrete members. The use of fiber-reinforced polymer (FRP) composites as a confining material for concrete has received significant research attention. Concrete-filled FRP tubes (CFFT) became a popular form of hybrid structural elements in rehabilitation or in new construction. Filling the FRP tube with concrete can provide compressive resistance and prevent local buckling of the thin tube (Roeder et al. 2010). The CFFT system can be also internally reinforced with steel reinforcement, as the tube can protect the steel from water infiltration and corrosion, while the steel reinforcement can provide ductility and additional strength as well as minimize slip of the tube relative to the concrete core, which can be a major factor in the loss of composite action (Abouzied 2016; Abouzied and Masmoudi 2016, 2017, Ahmed A. et al. 2018b). Therefore, utilization of FRP tubes filled with plain or reinforced concrete as a hybrid composite system can provide the proposed system many unique advantages, which makes it highly suitable alternative for use in the construction of sustainable and high- performance structures (Fam et al. 2005; Ahmed A. et al. 2018 a; Ahmed A. and Masmoudi, 2018;