Polish Roof Collapse Kills at Least 12

[Ussuri]

Units...I must admit I find the US way of doing things complicated, (kips, k-ft, psi, psf etc). I guess its what you are used to .

I did a little more digging in the Eurocode to see what it would have suggested for a snow load. I have never used it so, if I have got it wrong, please dont shoot me.

Katowice is in the south of Poland at an altitude of 284m. BS EN 1991-1-3:2003 Figure C.13 gives the snow map of Poland and from what I can gather the town is on the border of Zone 2 and Zone 3. The snow load on the ground sk=0.9 kN/m2 for Zone 2, and sk=(0.006*284)-0.6 but not less than 1.2kN/m2 for Zone 3.

There is also a requirement for an exceptional snow load, sad=2.0*sk=2.4kN/m2.

The corresponding snow load on roof (I have had to guess as I dont know roof pitch, GA etc) s=mu*Ce*Ct*sk or sad
giving s=0.8*1.0*1.0*2.4= 1.92kN/m2 (40psf) or 0.96kN/m2 (20psf).

Sounds like these ae still substantially lower than you apply in the US.

200psf = 9.6kN/m2 is very high. That is well in excess of the floor loading we use for say a plant or boiler room (at 7.5kN/m2), including weight of machinery.

 

[JStephen]

That 200 PSF is in a ski area, with exceptional snowfall, not very many places in the US would be designed for that.

As to the US units being complicated...all through school & college, we are taught the SI system- then find in the real world, people are using kgf/cm^2 and other oddball units. And even the SI system has its oddities- why is the fundamental unit a KILOgram, and not a gram?

 

[Ussuri]

Good question, I have absolutely no idea.

I guess when they were picking the seven base units for the SI system someone had an off day, because length is in metres as opposed to KILOmetres.

 

[JAE]

Most of the snow loads in the US vary from 0 in the southern half (using roof live load = 20 psf) to around 20 to 30 psf in the mid states to 60 psf in the far north (I think Maine has 100 psf ground snow in the far north regions).

Out west, with a drier climate in the mountains, the snow load drops except in the higher altitudes of the mountains such as JStephens pointed out.

In my area (midwest - Nebraska/Iowa) the roof snow usually comes out at about 17 to 21 psf.

 

[Ussuri]

This was printed in the New Civil Engineer Yesterday.

Published 02 February 2006 at 08:00

Outdated loading codes triggered Polish collapse



Outdates snow loading requirements in Polish building codes have emerged as the key contributing factor to Saturday’s collapse of the flat roof of an exhibition hall in Katowice.
More than 60 people died in the tragedy and the search for bodies was still continuing as NCE went to press.
Around 500 visitors were attending a racing pigeon exhibition in the Katowice Trade Hall when the collapse occurred.

The seven year old, 100,000m2 building was experiencing the worst winter by far since it opened. It is reported to have had more than 500mm of compacted snow and ice on its roof at the moment of collapse.

The roof of the steel framed building is reported to have been designed to take up to 800mm of normal snow, then in line with the local codes.

But a recent analysis of Polish snowfall records over the last 50 years has found that in some areas the design snow loading should be up to 70% higher.

Recent prolonged sub-zero temperatures could also have increased the chances overloading from snow and ice.

“Under those conditions heat leaking through the roof can melt the lower layers of snow, which refreeze as ice when the heating is off,” said Steel Construction Institute director Graham Owen. “Over time the density of the ‘snow’ will approach that of water.”

Owen added: “The roof trusses were more than 10m above floor level. At that height any excessive deflection would have been very hard to spot.”

Dave Parker

 

[HgTX]

Speaking of SI, how normal is it to say "500 mm" rather than "50 cm" or even "half a meter" in that context? It's not like they knew the depth of the snow even to the nearest 5 mm.

Hg


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[Ussuri]

Generally speaking, in my experience, millimetres are used for all measurements, up to say 100 metres. But I guess it will depend on industry and application (eg roads).

For instance we rarely use centimetres, and I have never come across decimetres.

 

[HgTX]

Huh. In Israel the centimeter is the standard conversational unit, used in very much the same situations where we in the US use "inch".

Hg

Eng-Tips policies: faq731-376

 

[Ussuri]

Hg

Units used by the general public in the UK can be anything. I was taught centimetres at school, my family use feet and inches, miles etc. In day to day things (non-engineering) I will use a hotch-potch of units, metres, miles, gallons, pints, stone. I only use feet and inches when giving my height though.

At work however, its only millimetres for lengths and metres for levels.

Its all a bit of mess really, and I think as long as everyone is clear what unit is being used it doesn't make much difference.