Groningen in the Netherlands is the site of one of the largest natural gas fields in the world. Extraction started in the late 1950s but, after more than 30 years, it became clear it was causing seismic activity. At first this was on a fairly small scale but in 2012 a stronger earthquake raised the question of whether more severe life-threatening earthquakes were also possible. In response, a project was set up in 2015 to assess 120 schools in the area for seismic resistance and implement any reinforcement measures that were needed. Royal HaskoningDHV has been working on the project with contractor Visser & Smit Bouw in a joint venture known as VIIA.

Continuous improvement of models enables closer approximation to real situation

Over the years, our Advanced Technology & Research group has been involved in the seismic analysis of many more buildings and has developed increasingly realistic models and simulations of the impact of earthquakes on the buildings. This has enabled the work in the field to proceed at a faster rate. The team started with relatively simple 3D models to assess which structures were at risk. The advantage of such models is that they are comparatively quick. The disadvantage is that, because of the simplifications, there is a wider margin of error in the outcome, so assessments need to be more conservative. This adds cost. Also, strengthening measures such as concrete walls or steel beams may be unnecessarily intrusive and exaggerate the perception of risk for occupants.

To introduce more precision into the models, simulations were used. The non-linear time history models incorporate much more detail to provide a more realistic insight into behaviour. These advanced models are calibrated against lab tests carried out by Delft University of Technology. Over the years our models have improved to deliver close approximations to a full-scale lab test. This enables us to be more precise and less conservative in assessments of strengthening required. The results are also used to improve the application of the simplified methods. For some types of buildings, such as agricultural barns, the simplified methods are giving similar results to the most advanced methods, making the assessment process much quicker. 

Catalogue identifies which measures to use and when 

Just as important as the realistic simulations is the application of this research in the field. The results have been used to create an online catalogue. It identifies which reinforcement measures to use, when they are applicable, and which is best in particular situations. It automatically presents costs and visualisations. The Measures Catalogue has proved so successful that all the companies working on the project have been directed to use it. It has also won awards, including a Dutch Design Award in 2018.

Focus on continuous improvement to speed and efficiency

The Advanced Technology & Research group is continuing to analyse buildings and make improvements to the process and the retrofit measures. Members of the team now have considerable experience and are achieving results which are superior to the simplified models. By combining advanced methods with this practical experience, we are able to speed up the assessment process further, while ensuring it continues to be reliable.

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Project Facts

  • Client
    Client in Groningen, the Netherlands
  • Location
    Groningen, the Netherlands
  • Scope
    Assess and retrofit thousands of buildings to protect against earthquakes 
  • Solution
    Developed increasingly realistic models and simulations of the impact of earthquakes on the buildings

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