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 life, and some of them have already reached the end of it. TNO specialises in assessing the safety and service life of civil and other structures.
Replacing structures is expensive, so it is worthwhile finding out whether their service life can be extended. In many cases, a more detailed assessment of a structure shows that it still easily meets requirements. Replacement for technical reasons can therefore be postponed, and unnecessary expenditure is avoided.
During the past twenty years, TNO has specialised in assessing the safety and service life of civil and other structures. We use methods such as assessing load-capacity reserves, and we perform measurements and load tests to reduce uncertainty. We also assess and re-assess the safety philosophy for existing structures. In this context, TNO made an important contribution to the realisation of the structural standards for existing structures: NEN 8700 and NEN 8701. The methods used for this purpose help to assess service life more accurately and hence improve the reliability of structures. This prevents unnecessary replacement and therefore unnecessary financial outlay.
Prevention and repair
Degradation in materials is a determining factor in their long-term structural safety. Service life can be extended by anticipating degradation, making repairs or taking preventive measures.
- Steel and concrete
Extending the life of these two types of structure poses fundamentally different challenges. The service life of steel structures is largely determined by fatigue phenomena, which in turn depend on the traffic load to which the structure is subjected. The service life of concrete structures, however, depends on their load-carrying capacity under (quasi-)static loading. The increase in traffic in recent decades is having a negative effect on these phenomena.
Degradation is a threat to the reinforcement components in concrete. More than half the number of concrete structures have corrosion damage after 70 years. It is essential to prevent and repair corrosion and other damage in older civil structures to ensure they remain safe for the rest of their service life.