Design-oriented axial stress–strain model for partially fiber-reinforced-polymer-confined normal-strength concrete

Abstract

Due to the influence of “arching action” in fiber-reinforced polymer (FRP) partially confined concrete columns as a result of the unconfined regions, the confinement of the concrete columns wrapped with discrete FRP strips is less efficient when compared with full wrapping schemes. This study comprehensively investigates the difference of the the confinement mechanism between fully and partially FRP confined circular normal-strength concrete and thus presents a new design-oriented model to predict the stress–strain relationships of partially FRP confined normal-strength concrete. The formulas used to determine the strength and corresponding strain of several key points on the stress–strain curves are also proposed by the regression analysis according to a reliable test database from the relevant literature. Besides, another selected database including 100 FRP partially wrapped circular concrete columns is also collected for model verification. The results show that better performance can be achieved by the new model compared with the selected models in predicting the ultimate conditions of partially FRP confined concrete. Finally, some specimens are chosen to assess the performance of the new model in predicting the complete axial stress–strain curves. The comparisons reveal that satisfactory accuracy and good agreement can be achieved between the theoretical predictions and experimental observations.