Effect of unconfined concrete strength on the strength and deformability predictions of FRP confined concrete

There are several available models proposed for predicting the compressive strength and deformability of concrete confined externally with fibre-reinforced polymer (FRP) composites. In this study, the effect of variation of unconfined concrete strength on the predictions of several available models and code equations are investigated by utilizing an extensive experimental database containing test results of more than 600 specimens tested by different researchers. The performances of the models in terms of prediction of compressive strength vary significantly with a change in the compressive strength of unconfined concrete. Particularly the predictions are generally less accurate, when the unconfined concrete strength is relatively low. In addition, the safety margins of the code equations are not consistent for all ranges of unconfined concrete strength. Furthermore, the predictions of the existing models for deformation capacity are much less realistic with respect to their strength predictions.