Displacement and plastic hinge length of FRP-confined circular reinforced concrete columns

• Finite element models were developed and calibrated against six specimens.
• Plastic hinge length was measured for the calibrated specimens.
• Empirical models were proposed to predict the plastic hinge length and ultimate drift ratio.
• The finite element models were able to show the plastic hinge region.
• The proposed model significantly improved the ultimate drift ratio prediction compared to previous models.

Confinement of both existing and newly constructed reinforced concrete (RC) columns by fibre reinforced polymer (FRP) has been commonly used in recent decades. This is because of its ability to enhance the shear resistance and the ductility of the RC columns, which are the main parameters that govern the behaviour of RC columns under lateral loading. This paper presents a finite element (FE) model that was developed using the LS-DYNA program aimed at modelling the plastic hinge length (lp) for FRP-confined RC columns. A FE parametric study was conducted to investigate the effect of FRP-confinement on lp. Empirical models were proposed to predict lp and the ultimate drift ratio (δu) for FRP-confined RC columns and the results were compared with similar previous models. The proposed FE model was able to predict the plastic hinge region and lp value which can provide a simple way for designers to investigate the behaviour of FRP-confined columns during the design process. The proposed δu model reduced the average of errors (A) and standard deviation (SD) by 15.1%, 3.9%, respectively, compared to the best predictions by previous models.