Tension stiffening effect in GFRP reinforced concrete elements

The deflection of Glass Fibre Reinforced Polymer Reinforced Concrete (GFRP RC) is often the governing criterion for design. The lack of fundamental research particularly on the tension stiffening behaviour of GFRP RC has hindered both the development of fundamental equations to predict deflection and the use of nonlinear Finite Element (FE) analysis for predicting the structural behaviour of GFRP RC. This thesis investigates the tension stiffening effect of GFRP RC in an effort to improve the predictability of GFRP RC deformation behaviour. The study adopts a holistic approach for tension stiffening which considers the bond as the building block for tension stiffening modelling and tension stiffening as being a macroscopic representation of bond modelling. In this study tension stiffening is experimentally evaluated first against more generic variables like concrete strength, reinforcement ratio and bar diameter. This is followed by a detailed study on bond between concrete and GFRP which results in the development of a strain distribution function to represent bond between cracks. This formed the basis for the development of a comprehensive model to analyse the tension stiffening behaviour of direct tension tests. After evaluating the tension stiffening test results against existing code-based formulations, the CEB-FIP model is recalibrated to represent the tension stiffening behaviour of GFRP RC, thereby providing a simplified means to evaluate tension stiffening behaviour of GFRP RC. The successful implementation of the tension stiffening model is demonstrated through the prediction of deflection of flexural elements using a general nonlinear FE analysis package (ABAQUS) that uses the smeared crack approach to model the reinforced concrete behaviour.