Constitutive Model for Ultrahigh-performance Concrete Confined by Hybrid Fiber-reinforced Polymer Tubes

Fiber reinforced polymer(FRP) feature has obvious brittle,while the hybrid fiber reinforced polymer(HFRP) with low brittleness,has multiple fracture characteristics.To research the axial compression behaviors of ultrahigh-performance concrete(UHPC) confined by HFRP,thirty-six HFRPconfined UHPC cylindrical specimens were tested and the stress-strain curves were measured.The experiment shows none of the existing representative models provided a reasonable prediction for strength and strain of HFRP-confined UHPC specimen,therefore a new ultimate strength and strain perdition model considering the confinement effectiveness of different hybrid FRP series was proposed.The new proposed model presented the best fitting results.The stress-strain response predicted by the existing representative models are all below the experimental curves,therefore a new two-stage constitutive model was proposed,which relatively fits the test curves better than that of the existing models.The new proposed model form is simple for engineers to use.