Research

Many large reinforced concrete structures worldwide have been in service for several decades, during which their durability has gradually deteriorated due to environmental influences such as temperature variations, moisture ingress, carbonation, and chloride attack. As a result, the structural reliability of these systems has declined over time. In particular, critical infrastructure—including bridges and tunnels—is continuously subjected to repetitive loading and harsh environmental exposure, leading to progressive performance degradation. However, conventional maintenance and assessment approaches rely heavily on visual inspections, limited experimental data analysis, and empirical judgment, which are insufficient for comprehensively evaluating the overall structural performance. These traditional methods not only lack the capability to accurately predict the long-term behaviour of large-scale structures but also hinder the quantitative determination of appropriate maintenance and strengthening measures. Consequently, a more systematic and quantitative assessment methodology is required to support reliable decision-making for the maintenance and rehabilitation of reinforced concrete infrastructure. Furthermore, modern structural safety standards are becoming increasingly stringent, and many aging structures no longer satisfy current design requirements, necessitating thorough assessment and appropriate retrofitting strategies. Full-scale experimental validation of structural performance is generally impractical due to economic and technological constraints. Therefore, objective analytical methods based on reliability theory and digital twin technology are essential. Reliability-based approaches enable the quantification of uncertainties in structural performance using experimental and monitoring data, while digital twins provide high-fidelity representations of the current structural condition and facilitate the prediction of long-term performance evolution under varying influencing factors. Ensuring the safety of large infrastructure systems is a global challenge rather than a country-specific issue, and reliability assessment and digital twin technologies are actively being investigated worldwide. In regions such as Europe and South Korea, where new construction markets are largely saturated, the maintenance and monitoring of existing structures have become increasingly important. This study forms part of an international research project that utilises monitoring data from the Jauntal Bridge in Austria and aims to contribute to the development of a more reliable structural safety assessment framework through global research collaboration. The outcomes of this research are expected to support both the maintenance and the design of large reinforced concrete structures in Europe and beyond, thereby contributing to the sustainability, safety, and efficiency of infrastructure systems for future generations.

The project involves the development of an algorithm for a fiber-optic inclinometer measurement system (FOS) consisting of a cylindrical glass-fiber rod in which fiber-optic Fiber Bragg Gratings (FBGs) are integrated along the longitudinal axis. Based on the FOS measurement data recorded along the rod, the spatial deformation state variables are to be determined for both small and large three-dimensional deformations. In addition, local material stresses are to be derived and compared with defined limit states in order to verify ultimate limit states, serviceability limit states, and fatigue or durability limit states of structural components. For this purpose, an evaluation algorithm is developed within the project that converts the FOS measurement quantities into inclinometer, extensometer, and local strain information. This conversion is achieved by coupling the measurement data with a specially developed inverse finite element program and an optimization algorithm. The project builds on an algorithm that has already been successfully developed for an FOS lamella measurement system with a rectangular cross-section, in which two embedded fiber-optic sensors were combined into a single measurement system. The objective of the project is to further develop this proven lamella measurement system with a rectangular cross-section and two embedded fiber-optic sensors into an FOS measurement system with a circular cross-section and three embedded fiber-optic sensors. This new system is particularly suitable for measuring large deflections and complex three-dimensional deformations.

The project will establish an Integrated Research Centre (IREC) for advanced numerical and analytical analysis of reliability, performance, and service life of existing and new civil engineering structures such as bridges, tunnels, protective barriers, etc. The IREC will aim to integrate the knowledge and tools of the cross-border partners from BOKU-IKI and BUT-STM and offer a unified and efficient access and service to the target groups on both sides of the border. This synergy will enable easy cross-border transfer of parts of solutions to complex problems. Within the framework of its activities, the Centre will offer both knowledge transfer in the form of seminars and publications and direct application and consultancy activities towards partners from engineering offices and infrastructure operators and owners. The common services, methods and tools will be intensified and adapted to the current needs of the target groups and thus prepared for an optimized operation of the research centre after the end of the project. The research centre will be autonomous after the end of the project, self-financed by the funds raised by providing services to the technical offices and the professional community. Without the joint involvement of the two cross-border partners, the required comprehensiveness and availability of the services offered could not be achieved, and thus the necessary change in the approach of the professional community to the application of modern advanced numerical methods to improve and streamline the design and assessment of building structures and to ensure sustainable and reliable transport infrastructure. For the duration of the project, the research centre will consist exclusively of two founding project partners. Future expansion of the research centre with additional partners from research institutions or industry is not excluded, in line with the needs of future developments in the field and the needs of the programme regions.