3D laserscan creates virtual model with pinpoint accuracy
In addition to understanding the cause of the collapse, the club was keen to get the stadium safely back in action. Using a 3D laserscanner to scan the structure, we created a virtual model with pinpoint accuracy, and photographs ensured we had a record of the location of every part. This enabled us to quickly get agreement that the debris could be removed. We also initiated research into the safety of the remaining sections of the roof. Within two weeks of the collapse, we were able to provide the club with our initial findings and advise on getting the stadium back into safe operation.
After this, a thorough investigation was conducted, which followed the Delft University of Technology’s approach to forensic engineering. “The method requires every option to be investigated in turn, without jumping to conclusions. We looked at each aspect and were able to eliminate various possible causes one by one,” explained Erik Middelkoop, Royal HaskoningDHV Structural Design Manager.
Rigorous scientific research delivers solid evidence for causes of failure
Our research included a reconstruction of the incident. We explored historic loads and determined the impact of wind. We looked at snow loads, the recent addition of solar panels on the roof and the effect of rust. Simulation models were used to test roof connections, and laboratory research with an external company investigated the welds. We constructed a model of the stadium and undertook wind tunnel research to explore the forces in a storm.
“The impact of wind is complex,” said Erik. “The wind load is determined by turbulence and, if the façade is inclined or shaped, the angle of the roof will also have an effect. Computational assessments of wind load in these instances are not reliable, so when designing a roof like this, you either need to conduct research in a wind tunnel or use more conservative assessments.”
Conclusions accepted by all parties
The final report provides extensive examination and analysis of the situation and identifies three primary reasons behind the failure of the construction:
- The main cause is that the welds were too thin. Design flaws in the joints of the construction were a contributing factor;
- Strong downward wind forces, which were not accounted for in the roof’s design, caused the roof to collapse;
- There is a high possibility that the construction was already weakened during a heavy storm shortly after the stadium opened.
The scientific rigour of our investigation ensured our report and conclusions were accepted by all parties. Our research also underpinned conclusions reached by the Dutch Safety Board. The findings are being shared across the country through webinars to assist broader understanding and ensure similar design shortcomings are avoided in future.
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