Is it safe to cut a part of beam and attach another beam below?

[StaapEr97]

Hello,
We have had an issue where a pipe is running through a 150mmx150mm W shaped beam. Is it safe to cut a section (8") of pipe and attach a 100mmx100m W shaped beam below the cut with some overlap? Beam to be attached below cannot be more than 100mm as there is not enough room available. (Please refer to the attached image)

The main beam is simply supported beam of 28' length and having 3 supports between 2 ends. The cut will be at 27" away from one intermediate support on one side and 66" from other support. The beam carries it's self weight and 3 point loads of 0.25kips. One point load of 0.25kips is 4 inch away from the cut.

I'd be grateful for any insight on this. I don't need any detailed examination or anything, just wondering if anyone had seen this done.

 

[JLNJ]

No.

 

[phamENG]

This doesn't feel like a great idea, but I'm not going to be as quick to dismiss it. If you can satisfy shear flow requirements and moment transfer at the splices and handle stability issues with the beam, then it could probably work. Do you really have a 6" beam spanning 28 feet? I realize it's not that heavily loaded, but yikes.

So...why not move the pipe?

 

[Harbringer]

...just wondering if anyone had seen this done...

Nope

I don't need any detailed examination or anything..

I think this would require a detailed examination.

 

[dik]

Not a W4x4 but maybe a W6x6. It can be reinforced, using stiffeners the same thickness as the flange sections and proper welds to provide the same moment resistance along the full length... like a straight section, only difference is that deflection will be marginally increased. That's a pretty long span... just for beam self weight.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dhengr]

StaapEr97:
Yes, I’ve seen that done, but not quite that way. Per your request, I won’t go into any detail.

 

[MIStructE_IRE]

Oh dear, no.

Draw the force in the compression flange if you want to find out why this is bad.

 

[bones206]

What are the end connections of the existing beam? I’ve done something g similar in the past and there ended up being some apparent axial load in the beam that was unexpected. It was enough to cause some issues and required additional reinforcing at the area interrupted by the new pipe.

 

[dik]

...from a website...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Colostruct]

I tend to think of these sorts of situations like I would a beam to column moment frame and design accordingly. So, in theory, it is possible to do this as PhamENG mentioned. If this is in place and the beam is close to capacity, it will be a difficult field weld to get right.

BUT, I don’t have a good feeling about the span and beam size either.

 

[Tomfh]

You can do it but not as you’ve shown it. It needs an engineer to look at it. As it’s currently shown it will likely fail.

 

[human909]

Reiterating mostly what others have said/ Is there a solution? Yes. Almost anything is possible. Would it be anything like you drawing, no. You need an engineer.

On the topic on cranked beams. This was the inelegant solution some engineer came up with because the couldn't figure out a simple web connection rather than bearing connection for the gantry. The gantry is coming into the building from the front of the page.

I had to design the support at the opposite end and it was FAR simpler than their solution. Despite the fact that the support was a retrofit on a finished and built design AND had required a bearing connection with an sliding bearing. Sometimes people just make it hard for themselves and the fabricators.

 

[dik]

Ever try to get off a mailing list?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[dik]

This is one of my sillier things from 50 years back...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[StaapEr97]

@phamENG and @dik

Thank you for your response.
I'm sorry, I didn't had full information about the situation yesterday. I just got to know that the length of the beam is 28' and there are 3 intermediate supports between between two main supports. The span where the beam needs to be cut is 92" and the center of the cut is 27" (Right to left) from one support and 65" (Left to right) from other. There is a point load of 0.25 kips near the cut which is 16" (right to left) from support.

We are also trying to move the pipe, but it is already installed and it would cost a lot to relocate it.

 

[LittleInch]

I agree with the others here that this needs proper calculation and sign off and also some idea of the overlap length and how you intend joining the 4 x 4 bit? Welding? Bolts? Glue?

One option if a 4 x 4 is all you have room for is 2 off 4 x 4 side by side under the 6 x 6 with 1" of flange sticking out?

Or put a proper end plate on the 2 6 x 6 ends and insert a 6 x 6 between them if you don't need the full depth for the pipe.

Will still look like a complete bodge job.

Can't you just cut the 5" pipe and put in 2 or 3 off 3" pipes to span over the beam?

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[StaapEr97]

@Harbringer
Thanks for your response. Yes, we will surely have detailed examination before coming to any conclusion.

 

[StaapEr97]

@bones206

The length of the beam is 28' and there are 3 intermediate supports between between two main supports. The span where the beam needs to be cut is 92" and the center of the cut is 27" (Right to left) from one support and 65" (Left to right) from other. There is a point load of 0.25 kips near the cut which is 16" (right to left) from support. The supports are as pinned connections.

 

[Colostruct]

I would still have an engineer look at this to see if there is something I'm missing. But, could you span the entire 92"? If this beam is only carrying 250 lb, it seems like you could do something quite shallow. I would want to make sure the other spans do not have some sort of loading that requires the beam to be designed as continuous.

 

[rb1957]

as someone posted about "almost anything is possible" ... if you're willing to accept the consequences.

The beam reinforcement would be extensive. You could replace the entire 92" span (assuming the beam splices at these supports ?) and use a truss (heavy caps and webs or truss struts between) ... that would look like you planned it !? you could drop/lift the entire span ... depending how this fits with the rest of the structure.

that's key ... "the rest of the structure" ... is this a mod of an existing structure, or new build ??

the simplest is cutting the upper cap, running the upper chord over the top of the duct, add web, and add stiffeners to deal with the kick loads.

another day in paradise, or is paradise one day closer ?