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A new calculation method for assessing civil engineering works Iv-Infra Civil Engineering Works Lifetime Extension

More than a hundred civil engineering works

In the municipality of Den Bosch there are more than a hundred civil engineering works, divided between three parties, that need to be assessed. A sizable job with structural works of various ages: from hundreds of years to just 25 years old. These are fixed structural works, concrete structures and masonry bridges. The structural safety can be mapped in various ways. Iv-Infra tackles this by adopting a step-by-step, risk-driven approach, but why?
Every municipality and every manager needs to be fully aware of the load-bearing capacity of the structural works they manage. Having said this, the load-bearing capacity of a large proportion of the civil engineering works in the Netherlands is widely unknown, mainly because drawings of the designs and relevant calculations are no longer available. Some structural works are approaching the end of their technical life which presents risks. For example, an old bridge that can no longer withstand the pressure of holding a large truck. This is the reason why an inventory must be made of the structural safety of the civil engineering works and a determination made as to whether action must be undertaken.

Step-by-step

In order to gain or retain control over the structural safety of the entire area as cost-effectively as possible, Iv-Infra has developed the ABC (AreaalBeoordeling Constructieve veiligheid) approach. ABC stands for Area Assessment Structural safety. With the aid of the step-by-step (from 'general' to 'detailed') risk-based approach, the structural safety of the entire area is mapped, and prioritisation is compiled. In 2014 and 2015, Iv-Infra has mapped the risk of structural safety for more than 400 individual civil engineering works for the municipality of Den Bosch. In the first phase of the ABC approach, risk assessment is primarily based on the general characteristics of the structure. To save time and effort, constructive calculations are not yet carried out at this step in the process. However, an initial overview of the prioritisation is already gained at this stage.
It turned out that many of the civil engineering works ended up ‘in the red’, mostly due to much of the basic information being absent or unavailable. Therefore, the municipality of Den Bosch has in recent years invested in retrieving the design data from archives and reorganising it. Furthermore, Iv-Infra was requested to inspect almost all bicycle bridges, conduct constructive assessments and, if necessary, provide specific repair advice. Iv-Infra designed the QuickScan Bicycle Bridges for this. Thereafter, based on design data that became available and aspects important to the municipality, the municipality gave priority to all traffic bridges. There were more than a hundred civil engineering works that emerged from this. The municipality of Den Bosch has decided to investigate these structural works over the course of four years and to test them constructively against the applicable standards and guidelines. The municipality has contracted four parties to conduct the investigations and testing: Royal Haskoning DHV in combination with Nebest, Witteveen + Bos and Iv-Infra.   

A new calculation method

Again, the approach for each civil engineering structure is carried out in steps: with each step of the process, it is determined what the next step of the assessment should be. To achieve maximum cost-effectiveness, no more than what is deemed necessary is carried out. One of the greatest challenges is assessing the arches of masonry bridges. These bridges are difficult to assess as there are no existing calculation methods. Iv-Infra will, therefore, together with the two other contractors, test one of these bridges. Developed calculation methods can be validated from the results of the performed load test. Hopefully, this will lead to a trusted calculation method that can be used more widely in the market.
We will, of course, share the results of the load test and the new calculation method in a subsequent message!

Would you like to know more about the possibilities for your project? Wouter will be pleased to share ideas about your engineering issues. Contact him by email or call 088 943 3200.
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