Titel Deelnemers "Vibration monitoring and acoustic emission sensing during progressive load tests of corroded reinforced concrete beams" "Menno Van de Velde, Eline Vandecruys, Els Verstrynge, Edwin Reynders, Geert Lombaert" "Fracture mode analysis of cementitious mortars by simultaneous application of 4D-XCT and acoustic emission technique" "Charlotte Van Steen, Jeroen Soete, Mina Sarem, Martine Wevers, Stijn François, Els Verstrynge" "Cementitious brittle construction materials are susceptible to fracturing due to their heterogeneous material composition and relatively weak bond between the aggregates and paste. Hence, enhanced methods of fracture analysis in these materials are an important subject of research. The acoustic emission technique (AET) is frequently used in the study of brittle construction materials, yet the random nature of cracking and the het erogeneity of materials strongly affect the AE results, and necessitates verification of AE data with comple mentary monitoring techniques. Therefore, in this work, a test setup is developed where fracture during Brazilian splitting tests is simultaneously monitored by AE sensors and X-ray computed tomography (XCT). The novel test setup is designed to incorporate AE monitoring into in-situ step-wise load tests of cementitious mortar samples inside an XCT scanner. Digital volume correlation (DVC) of the XCT scans allows in-depth analysis of the fracture mechanism and validation of the AE results. Using DVC the damaged zones with high shear and tensile strain values were identified in addition, the X-ray images were used to investigate the influence of heterogeneities in the overall failure modes. For the AE-based damage localization, three arrival time estimation methods are assessed, with the Akaike Information Criterion (AIC) showing a 50–75% improvement in locating AE sources within the cracked zone. In addition, two AE-based fracture mode analysis methods are compared with the DVC strain field plots. Using both average frequency and rise angle analysis (AF/RA) and peak frequency (PF) analysis, 80–100% AE events in the shear strain zone were able to be classified as shear mode. PF showed better performance in the early load stages while AF/RA showed consistent results throughout. In general, the shear and tensile crack mode classification of the AE events agreed well with the shear and tensile strain field plots." "A two-phased modelling approach for corrosion-induced concrete cracking and bond deterioration in reinforced concrete" "Charlotte Van Steen, Rutger Vrijdaghs, Els Verstrynge" "Experimental study on acoustic emission sensing and vibration monitoring of corroding reinforced concrete beams" "Eline Vandecruys, Menno Van de Velde, Edwin Reynders, Geert Lombaert, Els Verstrynge" "Fatigue fracture quantification in brittle cementitious materials using acoustic emission testing and digital image correlation" "Mina Sarem, Stijn François, Els Verstrynge" "Fatigue loading in brittle materials introduces damage at the micro-scale. These micro-fractures can accumulate and cause a significant reduction in material stiffness or even lead to structural failure. Deformation-based monitoring techniques can be inadequate when detecting damage at the micro-level. Hence, here is where advanced non-destructive testing (NDT) methods such as acoustic emission testing (AET) and digital image correlation (DIC) can provide a significant improvement in quantifying fatigue damage. The paper aims to combine AET and DIC for advanced fatigue damage analysis on brittle cementitious mortars. Cylindrical samples with three different sizes are subjected to fatigue loading in a Brazilian splitting test. The damage advancement quantified from cumulative AE event count and energy analysis showed a good correlation with the tensile deformation measurement of the DIC. It was observed that for low cycle loading, the slowly progressing damage evolution may not always occur, instead abrupt failure similar to monotonic loading can occur even after passing several load cycles. The size of the fracture process zone (FPZ) was measured using several AE-based and DIC-based methods. The comparison of the approaches indicated that the AE energy-based method is the most suitable to quantify the FPZ size during fatigue damage progress. From AE-based FPZ analysis of the experimental results, it was concluded that for low-cycle loadings, the lack of a well-developed FPZ can be a cause of the sudden brittle failure." "Micromechanics-based variational phase-field modeling of Brazilian splitting tests" "Mina Sarem, Jacinto Israel Ulloa, Els Verstrynge, Stijn François" "The simulation of the Brazilian splitting test can be challenging due to the presence of stress concentrations near the load points, which can lead to numerical problems and convergence issues. This paper aims to realistically model the Brazilian splitting test on mortar samples under monotonic loading, employing a micromechanics-based variational phase-field formulation. A micromechanics-based phase-field model connects the field variables at the macroscale and the physical dissipative mechanisms at the microcrack level, associating plasticity with the sliding of closed microcracks and damage with the growth of open microcracks. The distinction between these two mechanisms aids crack initiation and helps to overcome convergence issues. To further support convergence, a viscoplasticity regularization is embedded in the micromechanics-based phase field model. First, the homogeneous response of a single volume element is presented to demonstrate the effect of the viscosity parameter, and to provide insight of different failure modes that the model predicts. The model is next calibrated against experimental results. Hereto, Brazilian splitting tests have been performed using Digital Image Correlation technique. The calibrated numerical model predicts shear fracture mechanisms involved in the Brazilian splitting test and this has been further explained by studying the effect of confining pressure on modulated failure modes in the model. The calibrated parameters are then used for other samples with the same material but a different size and boundary conditions to assess the validity of the model and its prediction capabilities. Results show that the numerical failure prediction is consistent with the experiment. Overall, the calibration and comparison of numerical and experimental results confirm the validity and reliability of the simulation model and its ability to predict material behavior and fracture modes under different boundary conditions." "Experimental Datasets and Model Uncertainty of Empirical Relations for Rebar Corrosion Assessment" "Els Verstrynge, Constantijn Martens" "Reinforcement corrosion in concrete structures entails numerous interacting parameters and processes. A general approach is to use corrosion-rate models to predict the corrosion level of existing structures, and subsequently update these predictions by means of on-site data. In this process, empirical models are often applied that relate the observed damage, such as corrosion-induced cracks, to the corrosion level. In this paper, an experimental dataset is presented that links crack widths and rebar corrosion, and model parameters are analysed. The results suggest that the corrosion length has a larger influence on the equivalent crack width than the cover/diameter ratio for samples with local corrosion. Further-more, a model validation was performed on three empirical relations for accelerated corrosion, showing the importance of the calibration dataset and additional input parameters on the model error." "Corrosion Level Prediction with Acoustic Emission Sensing and Crack Measurements" "Eline Vandecruys, Charlotte Van Steen, Constantijn Martens, Geert Lombaert, Els Verstrynge" "Quantifying Uncertainties in the Performance Prediction of Existing Concrete Structures using an Extended Direct Stiffness Method Approach" "Els Verstrynge" "Analyse van schade: over lezen van scheurpatronen en luisteren naar degradatie" "Els Verstrynge"