Wind engineering insights to create a safe replacement for a stadium roof after a near-catastrophic failure.
On August 10th, 2019, a portion of AFAS Stadium’s roof collapsed onto the spectator seating below. Fortunately, the stadium was not in use at the time and there were no injuries. While there was moderate wind on the day of the failure, structures are designed to withstand far more intense conditions.
The venue’s football club, AZ Alkmaar, had two urgent needs:
- To understand precisely why the structure, at just 12 years old, had failed.
- To create a safe new roof that could be integrated into the rest of the existing facility.
The engineering consultancy firm RHDHV, a European leader, was selected to help the venue’s owners evaluate the earlier design and safely rebuild. RHDHV engaged RWDI for wind engineering insights–drawn in by our experience in delivering design guidance for major stadia throughout North America and Europe.
“During the investigation of the AFAS Stadium roof, it was vital to have accurate wind engineering analysis from a renowned company. RWDI’s expertise and experience provided quick and valuable insight to find the cause of the collapse,” explained Wouter Meijers, Structural Engineer, RHDHV.
RWDI began by studying wind loads on the original roof structure. Utilizing our world-renown wind tunnel expertise, we created and tested a scale model, capturing wind effects from many directions and a range of surrounding scenarios. This analysis helped examine the precise dynamics of the interaction between the wind and the structure.
Our studies and the advanced analysis by RHDHV made it clear that low-cycle fatigue due to years of wind loads and the poor conditions of the welds was key to the failure. As wind passed over the upwind portion of the roof structure, it created turbulence that caused excessive downward wind loading in the roof on the opposite side of the playing field. Over time, this effect weakened some of the welding connections, which ultimately gave way. Although corrosion and other issues were present, they were only superficial and in non-critical parts. Long term exposure to dynamic wind excitation was the primary cause of the collapse.
Equipped with a complete understanding of the failure, RHDHV developed a design for a safe new roof for integration into the facility. RWDI subjected the new structure to rigorous wind tunnel testing and analysis, validating its performance in diverse conditions, with the goal to ensure that AZ Alkmaar fans will be able to safely cheer on their team for years to come.