BUCKLING FAILURE under heavy snow loading is thought to be the most likely cause of the collapse of a thin concrete shell roof over a leisure centre in Moscow last Saturday.
At least 25 people died when the Russian designed, Turkish built roof over the leisure pool in the Transvaal Water Centre crashed down on the crowded floors below.
Commenting on the few precollapse photos of the complex available as NCE went to press, Buro Happold partner and Millennium Dome designer Ian Liddell expressed concern at the apparent low degree of double curvature on the roof.
'The valley where the two curved sections meet is a reentrant area, where the roof effectively curves the wrong way, ' he said.
'This is a known problem with thin concrete shells. Shear loads are high here, and there is little resistance to buckling.'
Local reports said there had been heavier than normal snowfalls in the days before the tragedy.
But the two year old structure was the only major Moscow building to suffer significant damage.
Design snow loading values in Moscow building codes were increased by 50% last year.
Settlement has also been suggested as a possible cause. Tubular steel columns supported the shell roof, with loads transferred through sliding joints to a raft foundation.
Local engineers said large volumes of contaminated land were apparently removed from the site and replaced with imported fill before the leisure centre's foundations were constructed.