Cyclic Compressive Behavior and Load-Strain Model of FRP-ECC-HSC Composite Columns

An innovative composite column, which consists of a high strength concrete (HSC) core, engineered cementitious composites (ECC) ring, and fiber-reinforced polymer (FRP) tube, has recently been developed and subjected to monotonic axial compression testing by the authors. In this study, the cyclic compressive behavior of this proposed FRP-ECC-HSC composite column was examined. Test parameters, including HSC core strength, FRP tube thickness, and ECC ring thickness, were investigated. Typical failure modes, dilation behavior, and axial load versus axial strain behavior were discussed and analyzed. It was found that the FRP-ECC-HSC composite columns exhibited improved deformability, compared with the counterpart traditional FRP-confined HSC columns, with the ultimate axial compressive strain increased by 0.7%-69.1% for the tested specimens. Meanwhile, the ultimate axial strain for cyclically loaded specimens is larger than that for monotonically loaded specimens in general, indicating a delayed column failure. Cyclic axial load-axial strain models, including the envelope model, unloading and reloading models, plastic strain equation, and stress deterioration equation, were proposed to predict the cyclic compressive behavior of the tested specimens. The proposed model was verified with the test results and exhibited good performance.