Measurement of axial stress distributions in FRP-confined concrete columns using Tekscan pressure sensors

Strengthening of reinforced concrete (RC) columns through the provision of lateral confinement using fiber-reinforced polymer (FRP) jackets is now a widely accepted technique. While the behavior of concrete uniformly confined with FRP, as is found in FRP-confined circular concrete columns under concentric compression, is now well understood, there is much less understanding of the behavior of concrete non-uniformly confined with FRP (e.g. FRP-confined rectangular columns under axial compression). A major difficulty with existing studies on concrete columns under non-uniform FRP confinement lies in the lack of knowledge of precise stress distributions in such columns, and as a result, direct verification in terms of internal stress distributions of analytical/numerical models for FRP-confined concrete in these columns has been impossible. Against this background, the present paper presents the first ever study on the measurement of axial stress distributions in FRP-confined rectangular columns under concentric compression using a new pressure mapping technique. The measurement technique is first introduced, and the procedure for obtaining axial stresses in FRP-confined column is then explained. A comparison between the experimental results and the predictions of an advanced finite element model is next given, which provides mutual verification of the two methods.