Beams and their affect on Automatic Fire Detection

[Graeme]

I have been on a couple of sites recently and noticed that a few rooms have had the ceiling quartered by exposed H-beams.
In the middle of the room was one smoke detector.The beams are greater than 10% of the ceiling height so i would have counted them as a wall and had a detector in each section.
The only thing i noticed that the beams are different to the normal type as they had(and excuse description without a picture) large hexagon holes along their length.I guess for cosmetic looks maybe?The top of the hole would be approx 40mm from ceiling.
Is there any reason to discount these beams as four seperate walls or do the holes make a difference?
I would say no but would like to be sure.

Thank you

[Chris Houston]

I've not got the time to re-read the BS, but if the barrier to smoke movement is only 40mm from the ceiling, I would be inclined to say it was OK.  (Speculation.)

The hexagaonal holes are most probably not cosmetic, I can't remember the term for it, but it is a common way to increase the strength of a H-beam to cut it and then weld it in a manner that produces this appearance.

[dave bev]

castellated beams christopher, castellated beams!

in making this post i would like to make clear that i have no interest in the manufacture, distribution or installation of these beams, and apparently no beams are hurt in the making therof.

dave bev

[Chris Houston]

Now, if I were not such an honest person I would now delete you post and edit mine.

[colin todd]

Aren't these Chinese beams with their testes removed, Davey??

[dave bev]

far too much time on your hands mr todd!

[Graeme]

I've not got the time to re-read the BS,

as far as i am aware according to BS a beam greater than 10% of final ceiling height should be regarded as a wall.It does not go into detail of types.

[Chris Houston]

I've not got the time to re-read the BS,

as far as i am aware according to BS a beam greater than 10% of final ceiling height should be regarded as a wall.It does not go into detail of types.

I also believe this to be true.

[Graeme]

anyone shed some light?

[Graeme]

Have another one.

A room far less than 100m2 with a sloping roof. 4 H beams run from the lowest point to highest.

At the highest point the beams are less than 10% of ceiling height but at lowest they are more.
A detector in the apex will cover the whole room,so do i count the highest point as final ceiling height and discount the beams?

Thanks

Graeme

[Allen Higginson]

Do you lie awake at night making these up Graeme??

[Allen Higginson]

Is the sloping roof less than 600mm high along the upright from its lowest point to peak? If so then (as you know) you treat it as flat so therefore the beams are dividing "walls". Otherwise in the apex (or within 600 mm will do.This of course all relates to the maximum height that the sensing element can be from the ceiling (in the case of a smokie!!)

[colin todd]

Yes, you do , as that is where the smoke ends up anyway.

[Graeme]

Do you lie awake at night making these up Graeme??

not this time as this was a room i looked at last week.Although it has popped into my dreams recently.

Thank you Colin and Buzz

[Graeme]

Colin

please can you clarify an ammendement to BS5839-1 regarding siting detectors within 1.5mm of lift shatfs etc [accomodation areas].

does this mean now only in areas where people stay? It seems like a daft obvious question but i like to be sure,

Thanks.