Explaining the riddle of effective moment of inertia models for FRP concrete beams

Abstract

The current provisions in ACI Committee 440 for calculating deflections of flexural structures reinforced with fibre reinforced polymer (FRP) bars or reinforcements require the use of an effective moment of inertia. Many equations giving its expression have been developed over the past years and show significant difference between them among the CEB-FIP and Benmokrane formula, largely used in literature are selected. The discrepancy of response curves shows that the variation between them can be explained by the bond character and tension stiffening effect. The comparison between responses of various FRP reinforced concrete (RC) beams shows a relative accuracy via the experimental data. For this object, an analytical expression is proposed to quantify the effective moment of inertia and accurately results are shown. Obtained results show a favourite accuracy using the novel expression of the effective moment of inertia model of an in-service FRP bars RC beam subjected to a monotonic loading.