Effect of ultra-high lateral strain capability on the performance of damaged concrete strengthening with PET-FRP: Test and modeling

The lateral confinement of fiber-reinforced polymer (FRP) has a significant impact on the deformability, strength, and energy dissipation of core concrete, especially for damaged concrete. To address the performance of damaged concrete strengthened with the large rupture strain of FRP (LRS-FRP), the effects of damage degree, confinement stiffness, and loading rate were analyzed. Results show that the strain efficiency factor of LRS-FRP made of recycled polyethylene terephthalate (PET) can be stabilized at a high value of 0.87 even with a high damage degree when used for strengthening cylinders, which is larger than other FRP (BFRP and CFRP) and agrees with PET confined undamaged concrete reported in existing papers. The test results indicated that the increased initial damage degree result in a slight decrease in ultimate strain and ultimate strength. The loading rates will improve the initial compressive strength of core concrete, this result in the increase of the reflection point stress of LRS-FRP confined concrete from the elastic stage to the enhancement stage. But, the tangent modulus of the enhancement stage is hardly affected by loading rates even though the core concrete is under different initial damage conditions. One strength model with good performance after evaluation and a continuous integrable and derivable model are incorporated into this new work, which predicts the performance of damaged concrete strengthening with LRS-FRP.