Check Moment for Weld Connections 1

[learntopay]

Hi all,

I am checking the weld connection between the SB1 and MB1 as shown in the picture uploaded. The SB1 is sitting on top of MB1. I wonder the if I need to check the tension induced by hogging moment in SB1 for the welding?
Some argued that the moment was taken by the member itself therefore no need to check the connection for moment induced tension.

I am a bit confused about this explanation. Could someone help me out here. Many thanks!

 

[HTURKAK]

What is the red lines ? a strut or column rigidly connected to the beam MB1 ?
If the beam SB1 supported by MB1 only , a small torsional rotation of MB1 will diminish the moment resistance and the beam SB1 literally will be simply supported.




He is like a man building a house, who dug deep and laid the foundation on the rock. And when the flood arose, the stream beat vehemently against that house, and could not shake it, for it was founded on the rock..

Luke 6:48

 

[SWComposites]

why not just bolt the two beans together and be done with it?

 

[DaveAtkins]

Oh boy, there was a rather heated discussion on another thread recently about moment transfer from cantilever beam to support.

I agree with HTURKAK, if this is a beam supporting a beam, the supporting beam will rotate torsionally and the small moment which is theoretically transferred can be ignored.

If there is a column directly below that has a fair amount of stiffness relative to the cantilever beam, then moment transfer should be considered.

DaveAtkins

 

[EngineeringEric]

As others have said, why? this looks like a whaler-type configuration on the sheet piles so why are we transferring the moment to the MB1? If you need to, I'd recommend putting two stiffener plates in SB! vs one in the middle, but still.... where is this moment going? If nowhere direct than don't transfer moment. If somewhere, then connect that element directly to SB1 even if MB1 is in the way.

 

[EngDM]

Are you thinking that the moment in the beam has to get transfered to the support? I'm assuming you're checking SB1 as a continuous beam and you are seeing negative moment at the support location. You don't have to transfer the negative moment load to a pinned support (they are moment released). Yes the SB1 beam has to be designed for the negative moment. Maybe if each span of SB1 was unequal length such that one flange of the MB1 beam is loaded more, and it would cause some torsion, but typically that can be neglected if the elements aren't stiff (as eluded to above by others).

 

[learntopay]

Hi all, thanks for the response.

The red line is actually column piles below, below is a sketch that shows part of the framing plan.
The MB1 is supported by the piles with a spacing of 5m, the SB1s connect on two sides. Considering pattern load, I understood that there is torsion in MB1, but what about the connection design.

In the structural model, I didnt release the moment at end of SB1, like EngDM said, I considered the SB1 as continuous beam, but are you saying that i dont need to design the connection for moment only if I consider torsion for MB1?

 

[phamENG]

There's actually a good article in Structure Magazine this month about it. Part 2 of a series on unevenly loaded welds. Might have some useful information for you.

Part 1

Part 2

Regarding whether or not there is moment...the answer is that there is, but not as much as you might think. What is your intended load path? Looks like MB1 is supporting SB1. Okay. What kind of angular deflection do you have? Can SB1 rotate that much while MB1 stays still and not a) fail the weld or b) cause permanent, plastic deformation in any of the connecting elements? If the answer is no, you need to transfer moment and stiffen everything to prevent that deformation. If it can, then it's going to act like a pin. If you don't know...well, I think should work on figuring it out, but in the mean time just connect it for the moment and make sure MB1 can handle the torsion (just remember...web stiffeners do absolutely nothing for torsion in an open cross section beam).