Lax work led to AFAS Stadion roof cave-in

Article posted by Coliseum, May 4^th, 2020

Image: Royal HaskoningDHV

Royal HaskoningDHV has wrapped up their months-long investigation into the August 10 collapse of the roof at AFAS Stadion in Alkmaar. The report points out that the roof caved in due to varied reasons prime among them being poor welding, design errors and corrosion.

Royal HaskoningDHV is an international, non-listed engineering consultancy firm headquartered in Amersfoort, Netherlands.

The 17,023-capacity AFAS Stadion is a facility which sits in Stadionweg 1, Alkmaar, Netherlands. It is utilized for football matches and is the home arena of AZ Alkmaar.

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AZ Alkmaar is a Dutch professional football club from Alkmaar and the Zaanstreek. The club plays in the Eredivisie, the highest professional football league in the Netherlands, and hosts home matches at the AFAS Stadion.

It did not even take seven seconds for the roof of AFAS Stadion to give in last year during August, but evaluating the reasons behind last summer’s roof collapse took months. Experts from Royal HaskoningDHV went into the minute details, like frame-by-frame CCTV recordings or weather reports from the moment AFAS Stadion first went on stream in 2006. The 17,250-capacity AFAS Stadion remains one of the more modern stadiums across the Netherlands.

Roof report

While not blaming anybody in particular for the roof cave-in, the 71-page report points out that a number of reasons attributed for the roof collapse. The direct cause was the strong west-south-westerly wind on August 10 last year which put downward pressure on the roof, and the roof was not so designed to resist the same.

But, the moot reason may be traced back to 12 years on January 18, 2007, just a few months after the venue opened its doors. This is when the first strong storm-kind strong winds blew which may have weakened the roof structure. Similar gusts were then recorded on January 18, 2018, and on both the occasions the wind blew stronger than on August 10, 2019, when the roof gave in – hourly average of 23 m/s, compared to 17 m/s last summer.

This is a new finding when compared to previous reports from the OVV (Dutch Safety Board) and interim report by the Royal HaskoningDHV.

Just days after the roof cave-in, on August 16, the Dutch Safety Board published its initial findings. The findings pointed to lax welding done at the top connection of the roof girders and their supporting columns. The top joints gave way first, and then the bottom ones cracked under wind pressure. While the welded connections gave in, bolted ones remained intact.

The roof crumbling due to downward pressure also indicates design flaws in the roof structure. The final report upholds this as one of the causes, pointing also to cracks in that portion of the roof that did not fall apart on August 10 but remained firm in place.

Coronavirus hurdle

The football club published the entire report online in order to maintain full transparency and welcomed the results. In late autumn of 2019, nearly the entire roof over the stadium was dismantled and plans for its replacement are in progress.

“Now, we can take a new step. In consultation with all relevant parties, we now focus on the future and we will start working hard as soon as we have left the coronavirus crisis behind us. Health is, of course, the most important priority at the moment, but we will keep you informed of the developments surrounding the new roof. Of course, the safety of our supporters and employees has the highest priority,” said AZ Alkmaar’s General Director Robert Eenhoorn.

Before the coronavirus outbreak, it was expected that construction of a new roof would begin. The new roof construction work would have been combined with adding further rows of seating in some sections to increase capacity of the stadium and create a more uniform seating bowl. However, with coronavirus creating chaos the world over, the club is still not sure how to go about the whole work and how the pandemic will impact these plans.

With expansion in mind, AZ has also been looking at increasing parking capacity around the stadium, as required by the city of Alkmaar. There are plans to expand to the P9 section (currently green area used temporarily as parking, south of the stadium). Talks with the city on that issue took place in February this year.

Roof collapse rewind

Last summer on August 10, fortunately while the stadium was not in use, strong winds prompted the collapse of the north-eastern stand’s roof right onto the seats below. One girder’s top welding gave way, pulling three further parts of the roof down as well. Although nobody was hurt, the stadium remained unused until December 2019, when it was finally deemed safe, following dismantling of other parts of the roof.

Coronavirus count

The coronavirus figures to date in the Netherlands stands at 39,791 and the death figures – 4,893.

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