Strategies for low limit maintenance thresholds and condition states for bridge structures

The objectives of asset management are to ensure secure service of the objects and/or network, to preserve the infrastructure capital and to maintain the function through their life cycle. Maintenance activities should preserve the performance and future serviceability in such way that an adequate level of reliability with respect to performance requirements applicable to the structure under consideration is preserved. Hence adequate and low limit maintenance should guarantee reliability, safety functionality, availability, maintainability, health and security, as well as environmental and economic performance at the politically agreed level of service. In order to arrange resources, the concept of condition‐states and minimum maintenance thresholds are widely used in context of maintenance planning in many European countries. However, there is no uniform approach defining and rating the condition‐states and setting the low limit maintenance thresholds. In general, national authorities or individual operators are using their own developments which consequently lead to different levels of service. In many cases, the models and criteria used are based on country‐specific experience with implementation of condition‐based maintenance strategies. Moreover, in some European countries, preventive maintenance uses both condition‐based and scheduled maintenance strategy, with certain maintenance measures carried out in a condition‐based manner and some other measures are planned/fixed at certain intervals. In this contribution based on the outcomes of IM‐SAFE project, maintenance concepts, condition‐state definitions and low limit thresholds of maintenance strategies of European countries will be presented, discussed and compared. In addition, a special focus is given to apply sustainable measures and to develop maintenance strategies respecting the European green deal scopes.