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.

Review and Assessment of Material, Method, and Predictive Modeling for Fiber-Reinforced Polymer (FRP) Partially Confined Concrete Columns

“…Before making predictions, the type of stress-strain behaviors is required to be known on the basis of material and geometric parameters. According to the results, for the first behavior, the proposed model precisely predicted the stress-strain responses for a normal stress concrete under partial confinement [49]. However, future work is required to establish more precise equations to estimate the strength and strain for the axial strain cases.…”

“…However, if the predicted ultimate strain and stress were not underestimated at the turning points, the recommended model would perform best. For further stress-strain analysis, a study was conducted to determine the comprehensive difference between the mechanisms of partially and fully FRP-confined circular columns with normal-strength concrete [49]. Regression analysis was used to propose a formula that was used to determine the strength and corresponding strain on stress-strain curves.…”

“…The figures on the right side are the pictorial proof of ruptures; however, the left pictures indicated FE simulations' corresponding failure modes as shear and crush failure [19]. (b) The stress-strain curves showing three segments, including an obvious transition portion as a link connecting both linear segments, for partially confined circular concrete with FRP, where Type-1 is indicated as an ascending stress-strain branch, and Type-2 shows a descending post-peak response where type-2 is further classified in two branches for which the readers are suggested to this study [49]. (c) The load-displacement curves and failure modes of experimental and numerical results, validating proposed FEMs [43].…”

“…Source: (a) is from an open-access article distributed under the Creative Commons Attribution License. (b,c) reproduced with permission [43,49] Copyright © 2024, Elsevier.…”