Evaluation of Existing Post Tensioned Bridges in Vienna (Austria) with NDT Techniques

Abstract This paper presents several case studies where state‐of‐the‐art NDT (nondestructive testing) techniques were employed to assess the condition of post‐tensioned bridges' prestressing systems. The bridges, located on highways in Vienna's core urban area, are subject to heavy traffic. The paper highlights the author's accumulated experience as an expert service provider (Ramboll Finland Oy) responsible for the technical NDT assessment of these bridge inspections, and as the client (ASFINAG Baumanagement GmbH), the operator and maintainer of these critical infrastructures. Given that the prestressing system in post‐tensioned bridges is vital for load‐carrying capacity, its condition is essential for ensuring both the functionality and safety of the structure throughout its service life. However, because these systems are internal, the prestressing steel is not visible (unknown condition) and the quality of duct injection, which is critical for durability and functionality of the prestressing, is unknown. As demonstrated in extreme cases, corrosion of prestressing steel can lead to sudden bridge collapses. This paper discusses seven bridge inspection projects (2022‐2024) in Vienna. Evaluations of duct injections were conducted in selected zones using ultrasound tomography and Impact‐Echo NDT techniques. Slightly invasive methods were used to verify the NDT results and estimate corrosion of the prestressing steel.