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Is it possible to splice a beam only on its web?

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Aytacoglu

Aytacoglu

Civil/Environmental
Dec 4, 2023
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Hi All,

I am currently designing a splice connection for a beam that is going to be cut at its end where a new section will be attached. I have attached an image of the proposed arrangement where the beam will be cut and the new section will be installed.

At this figure, it shows that the splice has both top and bottom flange plates as well as the web plate. However, due to site constraints and some existing beams that are present at the top flange and bottom flange, the contractor asked whether it is possible to only provide a web splice to avoid these issues.

My question is, I know that some software allow you to carry out design calculations for a web splice only (i.e. Autodesk ROBOT). However in theory, usually it is assumed that the web is only going to take the shear force and the flanges will take the bending moment. In this case, the splice connection is near the support, however it will still have some bending moment.

Do you think that providing only web connection would work?

I would appreciate any suggestions/comments on whether this is practicable and possible.

Thanks!

Figure_1_splice_xutpij.png


Figure_2_splice_o3jagc.png
 
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If the moment at this section is low, then you can probably get away with doing this. I would use standard holes to try and cut down the potential for some slipping resulting in a "kink" at this location.

I would over-do the design of the bolts by a bit to try and make the connection closer to a fully-restrained (FR) moment connection.

If there is significant load, significant moment at this section, or if deflection is critical, I would probably not go this route, and would try to figure out some way to connect the flanges to make a more traditional FR moment connection.
 
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Also, I would not use a program to design this without checking it quite a bit first. The programmer almost certainly did not envision a moment connection, so probably didn't program it for that.
 
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Is it possible to weld a plate with top flanges and bottom flanges each? This way, tension or compression transfer from one flange to other would be possible, if practicable.
Is autodesk robot using the input moment in calculating the connection capacity? You may check output calculations to verify this.
I think splice should be strong enough to have similar stiffness as that of the section itself, rather than being adequate for applied forces.
 
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Where little or no moment, this is done all the time... either with web plates or with clip angles.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik
 
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I'd be VERY careful due to eccentricity reasons. You really need to assume no moment transfer across the splice unless you intend on slip critical bolting. In which case need to suitably calculate the capacity of the slip critical bolting for the moment as well as the shear.

Though if you don't care about moment transfer, like others have said this is done all the time. Where I have continuous beams on both sides I'll often provide a shear only spice and calculate/model it assume no moment transfer.
 
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but you're showing a web splice together with cap splices ... which should be good ... ?

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.
 
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Thanks everyone for their valuable comments. Just for information, this is for a cable shaft where the applied loading is very minimal and at that particular location, the bending moment is around 6kNm which is quite low. That's why I was thinking to use this and use M16 bolts which should be more than sufficient..
 
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The splices plates are too short. Make them much longer. Lap it say 1000 with the main section of beam, and then extend the plates all the way, so they bears directly onto the bearing point, without having to detour in bending via the beam stub. Make the plates thick enough too that the combined moment of inertia matches the beam.
 
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With that low a moment, your shear might be fairly low, and even with slip critical fasteners, it may be overkill. M16s have fairly low slip critical capacity.

-----*****-----
So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik
 
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