A dozen mobile cranes were called in to provide emergency support after the roof collapsed at a one year old sports arena in Denmark in early January. The roof of the 2,000-seater Siemens Superarena in Ballerup, near Copenhagen, came down just two days before an international cycling event. Two 72m span trusses of the 120m long roof failed. The trusses were of glue laminated bowstring construction. The roof gave in without any warning, and although two people were in the arena no one was injured.
After the accident, the country’s leading crane rental company, BMS, and its subsidiary Krangaarden, supplied 12 mobile cranes to support the remaining 10 roof trusses from the outside while engineers from main contractor Hoffman worked from within to provide longer term support for the rafters. BMS also supplied all the necessary scaffold for use inside the building as well as a fleet of access platforms.
It is believed that the cause of the collapse may have been a simple error in engineering calculations. Though it was a cold winter’s day, the weather conditions were relatively mild and there was no overloading of the structure. All this will not be confirmed until investigations are complete, however, and a full report is presented to the Danish courts.
To save the remaining trusses, the mobile cranes raised them by 20mm while temporary scaffolding was fixed beneath, on the inside, for support.
‘Surveyors monitored the roof throughout while increasing the pull of the cranes in 500kg increments,’ explaind BMS managing director Søren Jansen. ‘Engineers told us precisely where the slings needed to be placed as we lifted two rafters at a time.’
BMS and its cranes stayed on site for the three weeks that it took to build the supporting scaffold. Since then it has had up to three cranes on site at any one time, helping out with various aspects of the repair job.
The nine cranes shown in the pictures supporting the remaining roof trusses are:
• a Liebherr LTM 1400 all terrain (400t)
• a Liebherr LTM 1300 all terrain (300t)
• a Liebherr LR 1280 lattice boom crawler (280t)
• a Krupp KMK 6250 all terrain (250t)
• a Liebherr LTM 1225 all terrain (225t)
• two Krupp KMK 6200 all terrains (200t)
• a Gottwald AK 210 lattice boom truck crane (200t)
• a Demag AC 120 all terrain (120t).
