Characterization of concrete tension modulus, softening, and stiffening using distributed sensing

To design and assess reinforced concrete (RC) structures more accurately thus enabling more efficient use of materials, improved material models are required. Distributed sensing technologies have the potential to provide the data to support the development of these improved models. In this study, twelve specimens with varying types of concrete and reinforcement ratios were monitored with distributed fibre optic sensors (DFOS) and digital image correlation (DIC) while being loaded in direct tension. Strain data from DFOS and crack width data from DIC were used to quantify three material models required for accurate analysis: the concrete Young’s modulus prior to cracking, tension softening, and average and distributed tension stiffening. The results showed that the uncracked concrete stress–strain response was non-linear leading to a non-linear Young’s modulus. Reinforcement ratio was found to influence cracking strength, tension stiffening, and tension softening, which many current models do not consider. Tension softening was observed at larger surface crack widths than in plain concrete that form the basis for existing tension softening models. Lastly, crack spacing was found to influence tension stiffening behaviour. Each of these findings suggest that current models do not fully capture the behaviour of RC and that there are opportunities to improve RC analysis techniques.