Nonlinear tension stiffening and cracking behaviour of concrete reinforced with EN 1.4301 and EN 1.4482 stainless steel rebars

This paper presents an experimental investigation into the tension stiffening behaviour and crack formation of concrete elements reinforced with stainless steel rebars. Specimens reinforced with 12 mm diameter cold-rolled austenitic EN 1.4301 and 16 mm diameter hot-rolled lean-duplex EN 1.4482 stainless steel rebars were tested under uniaxial tension, with strain and crack development monitored using a Digital Image Correlation (DIC) technique. The study compares the tension stiffening stress–strain responses and cracking behaviour of stainless steel and conventional B500C carbon steel rebars, showing broadly similar behaviour up to first cracking, but with differences emerging due to the nonlinear stress-strain response of stainless steel. In particular, stainless steel rebars exhibited a less pronounced tension stiffening effect in 12 mm bars, comparable behaviour in 16 mm bars and a continuation of tension stiffening beyond the 0.2 % proof stress that gradually decayed towards the bare rebar response. The applicability of codified models from Eurocode 2, Model Code 1990 and Model Code 2010, including those for tension stiffening, crack spacing and crack width prediction, is assessed for stainless steel rebars. Finally, an improved tension stiffening model for stainless steel rebars is presented, based on Model Code 1990, Model Code 2010 and Eurocode formulations and incorporating the Ramberg-Osgood stress-strain relationship.