Fibre optic measurements and model uncertainty quantification for Fe-SMA strengthened concrete structures

This investigation aimed at studying a novel strengthening method using ribbed memory-steel bars by means of quasi-static load experiments and computational modelling of large-scale concrete members in flexure. The first part of the study focussed on the strain in activated and non-activated memory-steel bars measured with a distributed fibre optic measurement system during external loading of strengthened slabs. In the second part, a computational cross-section analysis model was developed and enhanced with two uncertainty quantification methods: sensitivity analysis and Bayesian model calibration. The distributed fibre optic strain measurements enabled detailed monitoring of the peak strains owing to concrete cracking. The strain data was post-processed to obtain axial stress and bond shear stress in proximity to the largest bending crack. The sensitivity analysis provided the relative importance of the calibrated input parameters and their interdependencies. Model calibration quantified the uncertain parameters such as prestress, concrete parameters, and memory-steel constitutive laws, resulting in good accordance between the model and the experiments. The models were validated by independent strain measurements. Parametric studies enabled prediction of the effects of the investigated strengthening method on similar concrete members with different prestress, materials and geometries.