Retrofitting external RC beam-column joints of an ordinary MRF through plastic hinge relocation using FRP laminates

Abstract

This paper presents the results of experimental and numerical investigations on flange and web -bonded FRP retrofitting schemes for external RC joints of moment resisting frames. Two, identical full-scale external joints are designed and constructed according to ACI318M-11 requirements for ordinary moment resisting frames. Quasi-static cyclic loading tests are then carried out on the specimens and some seismic performance parameters including strength, ductility, energy dissipation and stiffness are evaluated and compared. Numerical analyses are also carried out to study the effects of FRP overlay length on required number of plies for plastic hinge relocation and joint strength. It is found that successful relocation of plastic hinge away from the face of the column into the beam is possible with appropriate number of FRP laminate plies and overlay length. It is also found that as the length of the FRP laminate over the beam flange increases, the joint strength is enhanced; however, larger number of plies would be required for plastic hinge relocation.