span part of steel

[george765]

I have a few steels that are for a loft conversion as specified by SE. I have a question regarding the span of one of these steels.
The steel has lugs welded on the ends which insert into the web of two other steels (shown as c on drawing). There are lugs welded to steels c for connection.
My question is... which would you say is the correct 'span' for the joist, A which includes the lug or b which doesn't.
i.e. the 'span' of this steel detailed by the SE is 3.5m should length A or B be 3.5m ?
I am interested in your opinion.
thanks

 

[pilsbury]

You don’t want to take my advice, but I’d guess measurement b is the span. My reasoning is that I’d want to know the distance between beams once in place not including tabs that insert into webs.

Why are you asking. Do you think there has been a cock up sonewhere?

 

[george765]

Thanks for replying, yes I do think there's been a cock-up. I think the same as you, that B is the span. When I questioned the steel fabricator he said the 3.5m span from the SE always goes from centre steel to centre steel, That puts the distance between steels (we think the 'span') at 3350.
I will have to phone the SE in the morning, I hope we are wrong as there's going to be a lot of aggravation if the steels been cut short.

 

[pilsbury]

Well there is one bonus here - a SEs drawings and a steel fabricator. That means one of them is at fault and not you.

How do you know the beams are not correct?

 

[pilsbury]

on thinking about this further trying to put this into the context of the only steel beam I’ve ever ordered, mine was supporting a wall I removed. If I recall correctly the span was say 3.5m for arguments sake (the bit with nothing under it) and then I added some to this measurement for the bearing on either side.... say 15cm to sit on the padstone. So my beam was 3.8m but the span was 3.5m.....

Translating this to your application makes me think the unsupported bit is measurement B (the span) and the tabs are the bearing bits.....

But then again the steel fabs centre to centre measurement also sounds plausible to me as in reality I know FA about structural engineering..... but he might have buggered it up and be a fast talker!!!!

 

[george765]

That's the way I think.....bearing-span-bearing, the SE will tell me when I speak with him. It's possible the steel in question is correct length, the fabricator is experienced, but like you say, he could of made a cock-up and trying to talk his way out of it.

 

[tony1851]

Was the SE working from drawings you supplied? It is generally up to the client/builder to provide the necessary dimensions, and the SE works back from those. Is it a case that beams C are already installed, and the beam spanning between them is an incorrect length?

 

[Anstiss Ltd]

My fabricator when doing lugs like this takes the span to the center of the steels. Lucky for me the first time I needed a steel like this the other end rested on a wall. I always order an extra bit as to take of a chunk off once everything is built if ordering before.

 

[^woody^]

Why have you stated 4m span in the OP and then 3.5m from the fabricator and you think it is 3.35m. There can't be 500 - 650m bearings. No way.

"Span" is the distance between supports not including bearings. If it's bolted between webs, then its the distance between webs.

 

[tony1851]

Incidentally, that's not normally the way steel beams are connected together, as the load on the lug welded to the web of the supporting beam acts off-centre from the web and puts a degree of torsion on the beam.
The correct way is to bolt the incoming beam directly to the web of the supporting beam; two holes are drilled into the web of the supporting beam, and a welded end-plate at 90° to the web of the incoming beam has two corresponding holes in it. That way, the load is transferred directly to the web and not offset.

 

[george765]

woody, sorry my mistake, original post amended, should have read 3.5m.
tony, the SEs drawings state a 90degree bracket, bolted as you describe, fabricator has welded a plate into receiving beams instead. I'm gonna speak to SE about that too.
I will update this thread when I've spoken with him (SE)

 

[John D v2.0]

always goes from centre steel to centre steel,

Agree, looking at it entirely from a logical point of viewv I don't see how A or B could be specified in the order as it's not really a relevant measurement except for how the fabricator wants to cut things up. The only thing the se and builder would care about are how far apart the beams it's connecting to are apart.

 

[george765]

update......I just spoke with the SE and he said that the 3.5m quoted was planned centre steel to centre steel, just as the fabricator said. I'm surprised, and will have to move a padstone but at least things can move on.
thanks for all comments

 

[pilsbury]

Well knock me down with a feather. Perhaps I need to watch another YouTube video to become an expert SE.