Finite element model for predicting post delamination behaviour in FRP-retrofitted beams in flexure

To predict the debonding load, shear stresses and strain profile along the FRP-concrete interface for FRP strengthened reinforced concrete members, eleven 4.5m long RC T-beams are built and tested to failure, and their complete load-deflection responses are measured. Three beams are not strengthened and are used as control specimens while the remaining eight beams are strengthened with different amount of CFRP sheet. The same beams are analyzed using LS-DYNA nonlinear dynamic finite element analysis procedure. The predicted load-deflection curve of each beam is compared with its experimental counterpart over its entire loading range up to complete failure, and the two curves are found to be in reasonable agreement. The distinguishing feature of the present analysis is that it not just captures the initiation and propagation of the delamination process, but also the complete post-peak load or softening response of each beam. It is found that the response of FRP strengthened beams is not always brittle and that after the initiation of delamination, the retrofitted beams continue to carry load and undergo appreciable deformation.