Analysis-oriented stress-strain model for FRP-confined predamaged concrete

In the area of structural rehabilitation, extensive research has been conducted on stress-strain models for fiber-reinforced polymer (FRP)-confined concrete. Most of the existing models are developed from tests conducted under laboratory conditions. However, structural repair work on concrete structures is usually applied to damaged concrete, which has different mechanical properties compared with those of normal concrete. An analysis-oriented stress-strain model of FRP-confined predamaged concrete columns was studied in this paper for the first time. Two state-of-the-art databases, including the cross-sectional variables, concrete damage degree, and FRP-confined stiffness, were established by collecting 313 test data points from the literature. Parameters in the analysis-oriented stress-strain model were well developed for FRP-confined predamaged concrete. The proposed models are unified in terms of column cross sections, which can predict both FRP-confined circular and square columns by considering the factor of the corner radius ratio. The proposed model shows a good performance by comparison with test data.