Bond Behaviour and Crack Width Prediction in Non-metallic Textile-Reinforced Concrete Members

Non-metallic reinforcement not only facilitates a substitution of conventional reinforcing steel, but also allows for slender members with a reduced concrete cover or an increase in structural capacity, significantly improving the sustainability of concrete buildings. The ability of non-metallic reinforcement in advancing the ultimate limit state for concrete members directs attention to serviceability criteria, such as crack width limitation, which become decisive for design. These criteria need to be accounted for by adequate models, especially regarding the bond behaviour and tension stiffening effects. To characterise the bond behaviour and derive a crack width related value of bond stress, pull-out tests were conducted on a carbon and a glass fibre grid. The crack development under cyclic loading was focused using uniaxial tensile tests in which the reinforcement strain was detected with fibre optic sensors to approximate a mean strain value along the transfer length to account for tension stiffening. The results were used for a prediction of the crack width obtained in the uniaxial tests.