Determination of the Deformation Behavior of Concrete Structures Reinforced with FRP Bars: A Theoretical Study

The design of concrete structures with embedded non-metallic composite reinforcement (FRP) is becoming more widespread. The behavior of statically determinate concrete structures reinforced by this durable material is already widely understood and known. Usage of glass and carbon fiber reinforcement is also included in the new generation of Eurocodes for concrete structures. However, in common practice, we also encounter statically indeterminate structures such as continuous beams or slabs. In the case of traditional steel reinforcement of continuous beams, it is possible to assume a certain redistribution of bending moments and to use the principle of linear elastic analysis with limited redistribution in design. According to ACI 440.1R-15 and the new generation of Eurocode a moment redistribution of internal forces on continuous beams or other statically indeterminate structures reinforced with FRP reinforcement should not be considered, given the lower material stiffness and linear elastic behavior up to failure. However, in reality, a redistribution of internal forces can occur. Based on a limited number of studies and experiments that have been carried out in this area globally, there is a premise that some degree of redistribution of bending moment may occur in FRP reinforced indeterminate structures. The objective of this work is to support this assumption through an analytical study of the behavior of a concrete cross-section reinforced with FRP bars, demonstrating its potential for internal force redistribution. The aim of this paper is to present the results of an analytical study capturing the behavior of a concrete cross-section reinforced with FRP, the determination of the deformation characteristics of such a section, and the possible application of the results to a two-span concrete beam. The main emphasis is placed on the stress-strain diagram of concrete and its influence on deformation characteristics, mainly moment-curvature relationship.