A Stress-Strain Model Considering Bilinear and PostPeak Softening Behaviors for FRP-Confined RC Columns

Objectives: A model with more generalized scope than those in the literature has been proposed to predict the stressstrain response of Fiber-Reinforced Polymer (FRP) confined rectangular RC columns under axial compression. Methods/ Statistical Analysis: 255 columns with their experimental data were used as a basis for the model expressions. Their database included columns with aspect ratios ranging from 1.0 to 2.0. Furthermore, the cross sectional depth varied from 100 to 500 mm and the unconfined concrete strength varied from 18.3 to 51.5 MPa. Findings: Based on interpretation of the test results, bilinear and post-peak softening stress-strain responses are proposed as referencing models, respectively, for columns having a sectional depth of smaller or larger than 300 mm. The softening model is composed of a parabolic expression for describing the first stage of the response and two linear expressions for the second and third stages. The influences of aspect ratio and size of cross sections, number of FRP layers and internal hoop steel bars on the key features of the envelope stress-strain curve model (i.e. ultimate axial stress and strain) are all considered in the model. Application/ Improvements: Reasonable agreement was revealed between the analytical responses of the proposed model with the selected tested responses, confirming its ability to simulate the stress-strain behavior of FRP-confined rectangular RC columns of small or large sizes. Keywords: FRP-confined Concrete, Rectangular RC Columns, Stress-strain Model