An effective stiffness model for GFRP RC cracked flexural members

There is no complete consensus of researchers on the problem of evaluating tension stiffening phenomena in cracked flexural glass fibre-reinforced polymer reinforced concrete members and, therefore, various empirical correction factors are used in the existing weighted averaging techniques for obtaining consistent estimates of experimental deflection of traditional steel bars reinforced concrete cross-sections. This paper presents an alternative method for deformational analysis of cracked GFRP RC flexural members based on constitutive modeling, taking into account the direct or inverse approach to evaluating the post-cracking stress-strain response of concrete in tension. The effect of tension stiffening is defined analytically by the derived formula for the effective moment of inertia, omitting the empirical correction of the moments of inertia of the uncracked or fully cracked RC cross-sections. Analytical formulae are also proposed to derive the parameters of tension stiffening based on the test data of GFRP RC beams subjected to bending. The relative systematic and random errors of the method are considered in the statistical analysis, involving the experimental sample of deflections for 42 beams. The case studies of manual calculation of the mid-span deflection of the beams by using the proposed technique and the inverse analysis for deriving tension stiffening parameters based on of the experimental data are also provided.