Strength models for fiber-reinforced plastic-confined concrete

Many theoretical and experimental studies have been carried out on fiber-reinforced plastic (FRP)-confined circular concrete specimens, leading to a variety of models for predicting their axial compressive strengths. In this paper, a large test database assembled from an extensive survey of existing studies is presented and employed to assess available axial strength models for FRP-confined concrete. The test database is also deployed to examine the effect of various factors on the performance of FRP-confined concrete. This study shows that the confinement effectiveness of FRP based on reported test results depends little on unconfined concrete strength, size, and length-to-diameter ratio of test specimens and FRP type, but depends significantly on the accuracy of the reported tensile strength of the FRP. The inherent variation of unconfined concrete strength also causes some scatter of data at low confinement ratios. Using those test data with accurate FRP tensile strengths, only two of the nine existing models are found to give close predictions. A new simple model is finally proposed, based on the observation that a linear relationship exists between the confined concrete strength and the lateral confining pressure from the FRP.