Our work

Bridges and viaducts

Our infrastructure has approximately 40,000 bridges and viaducts. These civil works are subject to ageing, and at the same time traffic loads are increasing. That is why one of our focus areas is to extend the service life of existing bridges and viaducts. Structural safety must be assured, and remain so. TNO is able to responsibly (re-)assess the safety of structures in cases where the usual calculation rules are not adequate for this purpose.

TNO has a long record of research into design standards and the related knowledge of structures and materials. We are often asked to investigate the causes of damage. We use the knowledge we acquire through this work to sharpen standards. We also build knowledge by reviewing designs and carrying out recalculations.
Extending the life of bridges and viaducts requires knowledge of three areas:

  • The behaviour and strength of structures (specialist material knowledge)
  • The loads to which structures are subjected (related to the application)
  • The (probabilistic) design philosophy of structures.

TNO has in-house knowledge of all three areas.

Extending service life

The technical life of structures can be extended by, for example, obtaining more detailed information on their strength and on how loads affect their behaviour. One way of doing this is to carry out tests or complex EEM calculations. Analysis of the loads themselves can also show that the level of safety is higher than could be expected using generic standards. Carrying out measurements on structures and/or the loads to which they are subjected advances our understanding of their actual behaviour. Combining uncertainty reduction with background knowledge of design standards helps to assess structural safety more accurately. In some cases it can show that structures that were earmarked for replacement might still have a period of service life left. Our knowledge of repair techniques (e.g. cathodic protection) and of the repair of fatigue fractures in steel also helps to extend service life.

Our work on bridges and viaducts

  • Steel structures. Much of our research in this field relates to fatigue behaviour. Improved fracture-growth models for welded joints can show their safety or extend their safe life.
  • Concrete structures. When re-assessing safety we often use methods geared to the specific structure type.
  • Load. We develop load models to provide a more accurate picture of the loads to which structures are subjected. These include models for static load and fatigue load.
  • Extending service life. This involves several aspects: inspection, monitoring and repair, and knowledge of the effectiveness of repair techniques.
  • Monitoring civil works. By measuring how damage develops, it is possible to predict how it will progress in the future and to assess the consequences for safety.
  • Damage investigation. Because we are often involved in damage investigations, we have a sound knowledge of the practical situation. We use this knowledge to assess safety and determine appropriate measures.
Our work

Extending service life civil structures

Structures are designed to have a long service life. This is usually between 50 and 100 years. Many of the civil structures in the Dutch infrastructure are more than half way through their intended service... Read more



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