Plastic hinge analysis of FRP confined circular concrete columns

Experimental tests have identified that FRP confinement affects the plastic hinge length of reinforced concrete columns. Some tests found that the confinement increased the plastic hinge length; whereas others showed otherwise. The plastic hinge length as well as the drift capacity of FRP confined circular concrete columns are studied in this work through a combination of numerical simulation, experimental study, and mechanism analysis. Data regressions are employed to formulate the plastic hinge length, which is found to be closely related to the confinement ratio of FRP. The obtained plastic hinge model shows that FRP confinement increases the plastic hinge length at low confinement ratio; however, it has an opposite effect when the confinement ratio is high. The accuracy of the proposed model is verified by test results from 29 large-scale FRP-confined circular concrete columns.