Stress redistribution along the interface between concrete and FRP subject to long-term loading

Results of an experimental campaign concerning the long-term behavior of FRP plates bonded to concrete are presented. Four CFRP plates with three different bonded lengths (from 100 mm to 400 mm) have been subject to long-term loads by using a mechanical system designed to apply a traction force constant with time. The tests have been carried out in a climatic room with a constant temperature T=20 degrees C and humidity RH=60%, for about three years. The strain profile evolution with time along the bonded length has been recorded by using a number of strain gauges along the plates. An appreciable stress redistribution with time along the plate has been observed. A simplified viscoelastic analytical model has been finally used to reproduce the experimental findings, obtaining good matching between experimental and numerical data