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Old 12th December 2011
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Default Steel Ladder Beam Shear Capacity

Hi all,

Wonder if anyone can help? I'm trying to find the maximum shear capacity of a typical 305mm deep steel ladder beam.

I can't seem to find this anywhere on the web and suppliers only appear to be able to produce basic loading data sheets, without the shear capacity!

This may be given in BS EN 39, but I don't have access to a copy unfortunately.

If anyone could please provide a value backed up by the source of the info, it would be much appreciated,

Thanks in advance,

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Old 12th December 2011
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I'm sure its :
Allowed Shear 12.5kN
In Britain we used to drive on the left of the road.

Now we drive on what's left of the road
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Old 12th December 2011
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14.9kN shear from the details I have. I don't think any of the data sheets (Boulton and SGB) I've seen state this, just Safe Working Loads. Our Engineer has worked it back over through calculation to get the maximum shear and bending loads.
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Old 12th December 2011
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cheers for info gents,

i have heard from a few sources that the shear capacity is around this area (12-14kN). To be honest i'm massively surprised how low that is when compared to standard scaffold tube with safe working shear of 29.2kN (according to TG20:08).

I would expect the weld to be the weak point; but still, bearing in mind the rungs act under compression and you have 2No tube-chords resisting the shear, just seems low.

Anyhow, could still do with an actual figure & source to back it up if anyone has this, thanks again
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Old 12th December 2011
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We have tested the steel ladder beams and the ultimate shear limit is 40.0 kN which we reduce by a factor of safety of 2 to give a safe working shear of 20.0 kN.
SGB sure beams (ladder beams) have a maximum shear of 18.0 kN on their data sheets.
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Old 13th December 2011
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The OLD SGB figure for shear in a Sure Beam was always taken at 18kN. That said I have theSGB data sheets which I must admit are old 1998 and I do not believe they show a shear load. They do however give max allowable point loads and UDL's for various spans. Working backwards from the 1.52m span with 35.66 kN allowable UDL would appear to indicate an allowable shear of 17.8kN.

It is worthy of note that there are many varying "ladder Beam" designs.
When I started there were two similar beams one was a Sure Beam and the other a Ladder Beam one was 14" overall depth the other 14" centre to centre.
I have allways considered the correct construction for the beam to be a saddle cut and a full circumference weld.
Today you will find beams with flat ends on the verticals which is a much smaller weld surface in a much more confined area. There are also copy beams on the market with sub standard tube not the original 4mm to 1139 or the 3.2mm grade 50C.

If you are buying beams you need to obtain adequate information from your supplier if you are using existing stock you should take the time to look at what you have and make suitable allowances.
I hope this is of help

Last edited by Alan Reade; 13th December 2011 at 10:59 AM.
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beam, capacity, ladder, shear, steel

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