Loft Steel bearing

[Andy_J]

Are there any issues with bearing steel beams that are supporting the floor onto the existing brickwork?
Would rather do this than take out brickwork below the existing ceiling line to install a padstone. I want the bottom of the steel supporting steel to be roughly 25mm above the existing ceiling joists with the floor joist notched into the web of the UB. If i sit the steel directly on the brickwork then it'll mean i don't have to remove some of the ceiling and plaster board on the walls below.

Hope i've explained myself well enough.

Your help would be greatly appreciated!

 

[chappers]

No problems you can bear your steels on 12mm steel plate.

 

[Static]

Use same sized bearing plate in area as padstone required.

 

[Andy_J]

Cheers for that.

I was going to use a 440 long x 100 wide x 220 dp padstone so i presume using a 440 x 100 x 12mm bearing plate would suffice?

 

[Static]

Yep should be fine, unless your putting in a hugh beam with 2 or so storeys of load onto it.

 

[frank999]

I have exactly the same question ie my structural calcs specify concrete padstones (off the shelf Lintels cut to a specific size) ... I would preferred to have had steel plates specified.

I too wish to avoid damaging walls/ceilings in rooms below.

I see its suggested to use 12mm steel plate that are the same length as the padstones, every time I talk to anyone regarding changing the spec on the floor I'm told 'must be justified by calculation', could I assume my BC officer has the power to make a decision regarding this change from Padstone to steel plate without costly amendments to structural calcs.

 

[PaulJR]

I have exactly the same question ie my structural calcs specify concrete padstones (off the shelf Lintels cut to a specific size) ... I would preferred to have had steel plates specified.

I too wish to avoid damaging walls/ceilings in rooms below.

I see its suggested to use 12mm steel plate that are the same length as the padstones, every time I talk to anyone regarding changing the spec on the floor I'm told 'must be justified by calculation', could I assume my BC officer has the power to make a decision regarding this change from Padstone to steel plate without costly amendments to structural calcs.

Just email the guy who did your calc's and ask him the question, when he replies that it's OK (which he should) print the email and bingo you've sorted it.

 

[^woody^]

Bearing plates need to be designed just like a padstone would be.

The specifying of a plate or a padstone for situations like this, is the difference between a designer who is knowledgeable and cares and one that is totally crap

 

[tony1851]

If anyone's interested, this is from an old book (1938) on steelwork.
It is for working out the bearing plate thickness, but if you know the thickness, (1/2") and the load, you could work out the length of plate required.
It's in imperial, so figures would have to be converted, and presumably it uses the old permissible stress method, so 'W' would be the actual load.

Untitled

• tony1851
• 11 Jul 2012
• 1

 

[^woody^]

Don't we use BS5950 nowadays?

 

[frank999]

My Architect has specified 150mm high padstones, which will disturb the ceiling and wall of rooms down below, makes common sense for him to have spec'd steel plates to avoid this ... but that seems to be amiss with this particular character - I will broach the subject - but I feel I will get the cold shoulder - since he has pocketed his fee.

As I thought, it couldn't be as simple as converting the length and width of the padstone into 12mm steel plate.

I have found:
http://www.steelbeamcalculator.co.uk/freepadstonecalculator.aspx

But I know very little of Structural Engineering, how easy would it be to go off and do some reading to understand what numbers are needed, any pointers ? - my structural calcs have been run on CSC TEDDS (I assume software made for the job) - which shows the Beam Analysis and Design (BS5950), I cant find any calculations for the padstones on them though ?? should not calculations for these be on my paperwork ?

Thanks

 

[tony1851]

Don't we use BS5950 nowadays?

Er, what's that?

 

[tony1851]

I cant find any calculations for the padstones

If an SE does the calcs for a steel beam, it is usually assumed that he would do a calc. for the padstones required as well.
You could have a perfectly adequate beam to support the load above, but if it is supported on poor brickwork, without a proper bearing, it's no use to anyone.
You mentioned in a previous post that one of the pads was 900mm long If you can't see any calcs for the pads, my hunch is that the SE has just picked figures off the top of his head which would be 'on the safe side'. If so, that's not engineering, it's just guesswork.

 

[PaulJR]

The padstone is calculated to give an area of bearing to keep the pressure exerted on the masonry within it's load capability - ie 7N/mm² for dense concrete blocks, and up to 50N/mm² for (engineering) bricks. Padstones are manufactured with a compressive strength of at least 50N/mm².

The size of the padstone depends on the dimensions of steel bearing upon it, the load applied and the required area for the strength of the masonry.

The load is assumed to spread at 45° through the padstone, so the deeper it is, the longer it can be, padstones do not act as beams as they are unreinforced, and in direct bearing with the wall they sit on.

The size of a padstone, should take into account the condition of the supporting masonry.

Regards going off & doing a bit of reading, sadly it's a bit beyond that, it takes a few years at college to get your head around all the concepts.

(I am a freelance civil/structural engineer)

 

[tony1851]

The padstone is calculated to give an area of bearing to keep the pressure exerted on the masonry within it's load capability - ie 7N/mm² for dense concrete blocks, and up to 50N/mm² for (engineering) bricks.

The characteristic compressive strength of the masonry will of course be somewhat less than those figures.