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-   -   Joining an I beam (http://www.diychatroom.com/f19/joining-i-beam-148885/)

pcousin1 07-02-2012 07:24 AM

Joining an I beam
 
I have a 254 x 146 x 43 UB steel beam which needs to be cut in half to get it to its location. what id the best method of joining without having a plate on top and bottom of beam ?

Am thinking one plate across the web, or welding steel plates on the end and bolting together.

what bolts, plates would i need ?

Any help would be appriciated.

JonM 07-02-2012 10:47 AM

Just like they do on a bridge...plate on each side of web bolted together...use the same thickness plates as the web...and if you need it even stronger...weld the top and bottom flange

tony.g 07-02-2012 12:05 PM

Welding end-plates on and bolting the end-plates together might not be structurally the best way to do it, depending on load and span.
The most efficient way is top and bottom plates on the flanges, but obviously you don't want to do this. The alternative as JonM said is to weld the flanges together.
However you do it, it is critical that you do not only depend on web plates. The flanges must be effectively fixed together. Mid-span, the flanges carry all the bending stress (compression in the top flange: tension in the bottom) and the web contributes little. If you install the beam with only web plates, and without either welding the flanges, or fxing top and bottom plates, it will buckle.

jcarlilesiu 07-02-2012 12:36 PM

There is no pre-determined acceptable method for this.

All of the members of the W-shape provide some resistance to the loading. The web is your primary resistance to deflection and shear of the beam, while the flanges both resist torsion.

tony.g 07-02-2012 01:10 PM

Quote:

Originally Posted by jcarlilesiu (Post 956153)
There is no pre-determined acceptable method for this.

All of the members of the W-shape provide some resistance to the loading. The web is your primary resistance to deflection and shear of the beam, while the flanges both resist torsion.

Are you suggesting that he doesn't need to fix the flanges together?

Evstarr 07-02-2012 02:36 PM

I think he's suggesting that an engineer would need to spec the correct method of joining the parts based on the intended use of the beam.

tony.g 07-02-2012 04:45 PM

Quote:

Originally Posted by pcousin1 (Post 955982)
I have a 254 x 146 x 43 UB

(Looking back, your beam size seems familiar. Are you UK/RoI based by any chance?)

Daniel Holzman 07-02-2012 05:16 PM

What is amazing about this thread is that there is apparently serious discussion about joining a W shape together with absolutely no information about the loads on the beam, the location, the end support conditions, the type of steel etc. Learned discussion about which is better, welded plates, bolted connections, strength of flanges etc. This beam could be intended for a bridge, a crane, a house, an amusement park ride or god knows what. How can anyone seriously discuss something like proper joining technique for a potentially critical steel element without even bothering to ask what the intended use is? If anything on this forum has ever seemed like a job for a local, professional engineer, this one sounds like it.

pcousin1 07-03-2012 12:36 AM

Morning all,
Thanks for your replies.
Yes i am in the UK.
The beam is about 6m long give or take a few mm, and is to be used as a ridge beam in my roof, and also a slightly smaller one (203 x 133 x 30) as a front beam to support the floor joists.

thanks
Phil

Bonzai 07-03-2012 12:43 AM

Quote:

Originally Posted by pcousin1
Morning all,
Thanks for your replies.
Yes i am in the UK.
The beam is about 6m long give or take a few mm, and is to be used as a ridge beam in my roof, and also a slightly smaller one (203 x 133 x 30) as a front beam to support the floor joists.

thanks
Phil

You seriously need to hire a structural engineer ... This is not the sort of thing that is in the DIY category ... If you knew enough to be able to do this right you would not have to ask on an Internet forum. Don't take this the wrong way, but Daniel is absolutely right in everything he says. Nobody on here can answer this as you need a pro there to produce the correct engineering drawings based on what they see first hand.

pcousin1 07-03-2012 12:47 AM

Hi, thanks, been there done that, told him what i needed, he charged me over 1000 for plans, and to be honest, when i said i'd like it done this way, he said, "i only join them this way" think conned springs to mind and done fancy that again.

Bonzai 07-03-2012 12:55 AM

Quote:

Originally Posted by pcousin1
Hi, thanks, been there done that, told him what i needed, he charged me over 1000 for plans, and to be honest, when i said i'd like it done this way, he said, "i only join them this way" think conned springs to mind and done fancy that again.

When a structural engineer provides plans they typically assume some liability if the structure fails as a direct result of what they engineered ... So that's why they want it done a certain way and why they have to charge a certain amount to cover the liability ... Similarly with an architect when they do a code review of plans for permits.

As a general contractor I am merely trying to advise what is in the best interest of you and your family's safety. Call a different engineer if you don't trust the first one ... Or risk it if you prefer and hope the roof doesn't fall in.

tony.g 07-03-2012 05:50 AM

Phil; have you specifically asked your SE for a detail for connecting the 2 cut pieces back together?

pcousin1 07-03-2012 05:52 AM

He Just said he does not do them that way, which was really not very helpfulof him.

tony.g 07-03-2012 07:05 AM

1 Attachment(s)
Phil; there is no reason why the beam should not be cut and re-connected at ridge level.
The conventional way to do it (avoiding welding, which is difficult/dangerous at that height in a roof) is by using a plated connection - see attachment showing the principle.
The practical part of this is within the scope of DIY. However, calculating the length and thickness of the plates, and the sizing, specification and spacing of the bolts are not a DIY proposition.
Your SE will have calculated the loadings on the beam, and will have worked out the maximum bending moment. From this, he could have designed a suitable connection, but he is obviously not under any obligation to do this, unless you specifically requested he design a 2-part beam at the outset.
I think the only way you can get round this is to get a second SE just to design a connection, but that may be difficult because of the divided responsibilty should it go wrong. There is also the additional cost of the design, and the cost of fabrication. Would it really be that expensive to hire transport/lifting facilities to get the beams up in one piece?


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