Conference Agenda

The Koralm tunnel is a railway tunnel in the south of Austria. The segmental tunnel lining rings in construction lot KAT3 consist of seven prefabricated reinforced concrete tubbings. So-called measurement rings are equipped with 38 embedded vibrating wire strain gauges. They measure the normal strain in circumferential direction. The present work is focused on the strain data from nine measurement rings. They are located close to each other in a geologically interesting area near the Lavanttal fault system. The evaluation of the monitoring data includes computation of the normal stresses in both the circumferential and driving directions, as well as quantification of the utilization degree of the tubbings. This is done by considering the long-term viscoelastic behavior of mature concrete within the framework of a hybrid, i.e. computational-experimental, approach developed by Razgordanisharahi et al. [12]. Thereby, normal strain histories measured inside the tubbings are translated into stress histories using an integro-differential viscoelastic model. It is based on the assumptions of a plane strain state in the tunnel cross-section planes and a plane stress state in the planes parallel to the tangential plane of the midsurface of the tunnel lining. The utilization degree of concrete surrounding the vibrating wire strain gauges is determined using the Drucker-Prager failure criterion. The largest utilization degree determined in any tubbing is taken as the utilization degree of that tubbing. The central result of the present work is the visualization of the development of the utilization degrees in the nine measurement rings over the first two years after the start of structural monitoring. At the end of the evaluation period, the largest utilization degree of the measurement rings is approximately 42 %.

Impressed current cathodic protection (ICCP) is one of the typical methods to protect reinforced concrete from corrosion damage. However, continuous application of current will induce acidification near the anodic region and cause degradation of ICCP system. In this study, the chemical characteristics of cement-based matrix at anodic region under the effect of ICCP are evaluated by an integrated numerical platform. Validation is first conducted based on the available experimental data, then parametric study is done to investigate the key factors influencing matrix deterioration. Finally, possible countermeasures to mitigate anodic deterioration are raised. From this study, it is found that the pH value of pore solution at anodic region gradually decreases as the current applies, resulting in the decline of matrix conductivity as well as the protection efficiency, which becomes the main reason for the ICCP degradation.

This research proposes a deep learning-based semantic segmentation method using U-Net to de-tect internal cracks in concrete cores extracted from in-service structures, employing X-ray Computed Tomog-raphy (CT). A major challenge in deep learning-based crack detection is the extreme class imbalance in the dataset. In the dataset used in this paper, the crack class accounts for only 0.5% and the void class for 0.7%, while coarse aggregates, mortar, and background dominate the composition. To address this imbalance, multi-class classification approach was adopted, and a novel Class-frequency-aware Focal Loss (CFL) was proposed. CFL applies nonlinear weighting according to the occurrence frequency of each class, thereby enhancing learn-ing for minority classes. In the results, multiclass classification outperformed binary classification, and the proposed CFL achieved notable improvements in F1-score. However, the high detection sensitivity of CFL was found to be accompanied by an increase in false positives in regions such as mortar areas.

EDF’s long-term energy strategy involves extending the lifetime of its nuclear reactors, potentially
beyond 60 years. A key element in this objective is ensuring the durability of the concrete containment
building (CCB), which is essential for reactor safety. While most ageing studies focus on concrete and steel, the role of surface coatings is often neglected. These coatings, applied to limit leakage, significantly affect the drying process by acting as moisture barriers. This reduces drying shrinkage and creep, which are key contributors to long-term deformation. This study evaluates the impact of coatings on the CCB through a comparative numerical analysis. Two configurations were considered: one not accounting for coatings in its model and one modeling them. Thermo-hydric simulations providing temperature and moisture fields up to the 8th ten-yearly inspection on the CCB (VD8) were used in long-term mechanical computations. The results show that coatings can reduce drying rates, tensile stresses, and creep-related deformations, leading to a more stable long-term behavior of the containment.

This research includes experimental and analytical studies that revealed the mechanisms of the shear stress distribution along the adhesive-concrete interface of epoxy adhesive anchor fixed with a short embedded length (L=50 - 100 mm) and different diameter of the fixing hole (D=14 - 40 mm). The averaged shear rigidity was calculated with FEM that could be a representative value of all the adhesive layers and their adjacent interfaces. The achieved shear rigidity was used to compose a macro model based on the shear-lag theory. Its model enabled to make simulations with varied shear rigidity of the adhesive layer, finally finding the relationship between the interface properties and the shear stress distribution at the interface.

The Italian infrastructural heritage is rather dated, with a large number of reinforced concrete and prestressed concrete bridges built between the ‘50s and the ‘80s, having already exceeded their expected service life. In many countries, the qualitative assessment of bridge vulnerability often relays on defect-based indexes derived from visual inspections. Many of these defects are related to reinforcement corrosion, which can be-come important in case of aggressive environments and/or insufficient maintenance. This study focuses on the numerical investigation of the effects of increasing corrosion levels on the seismic capacity of an existing via-duct pier in a marine environment. The time-dependent failure mode, with the possible change in the location of the plastic hinge, and/or the occurrence of brittle mechanisms related to rebar buckling or to an anticipated rebar rupture caused by a progressive steel embrittlement, are analysed through finite element analyses.