LVL support fixed or pinned

[palk7 EIT]

Hi,

Are fixed connections possible in wood beams (LVL's) by placing it in a steel bracket and fully welding the bracket back to a col., attached a pic. Could it be considered as a fixed connection? If so, do those bolts have to be checked for the restraint there or the bolt is only to be checked for the shear load from the beam?

Thank you

 

[jayrod12]

Cantilevered moment connections like that in wood are highly frowned up in most people's eyes.

If having to do some form of moment connection, the key is more small diameter fasteners spread far apart. And no, you do not just design for the shear load from the beam.

Is this related to your other question regarding the 20ft long wind girt? I think you just need to design the girt as simply supported and up the sizing as required to work.4

 

[palk7 EIT]

Yes jayrod, its regarding the 20 feet wind girt just thought if it could be fixed then the size can be reduced

 

[palk7 EIT]

It's not cantilevered has support on the other end as well, by what you mean I guess the moment has to be de-coupled and that will act as a shear cut in the bolts

 

[jayrod12]

I wouldn't rely on that. For deflection, you could reduce your span slightly in your calculations to the clear distance between the saddle pieces. I could get on board with that. I know it's not a lot, but when it comes to things relying on L^4, small changes can add up.

 

[palk7 EIT]

Yes, I will try that route.
Jayrod12- Just in general when two HSS columns are spliced by end plates (wider than column perimeter.) and lap welded all around the four sides by adjusting the plate dimensions, do you know how would you check the bending moment capacity of that weld connection there? The goal is to reduce the hinge at that joint

 

[Craig_H]

I have never accomplished a moment connection in wood myself, but I understand that it has been done in some instances. Jayrod hit it on the head regarding large numbers of small diameter fasteners. It is my guess that one would need a large cross section in which to space the fasteners while keeping their component reactions (mostly) parallel to the wood grain. Something along the lines of the image below:

 

[jayrod12]

I'm not up to snuff on connection design, specifically checking the welds themselves for the applied loads.

However, if you're talking about having two HSS welded to a single plate. And both HSS members are welded fully to the plate. I'd be considering that as a continuous column, not a hinge. As moment will be transferred from one chunk of HSS to the other through the plate.

A sketch and some loads, along with a better description of the issue would help. And we would probably get some input from the guys who design that stuff all the time. I'd start a separate thread for that with a applicable title.

 

[palk7 EIT]

Yep, thank you!!

 

[KootK]

Just in general when two HSS columns are spliced by end plates (wider than column perimeter.) and lap welded all around the four sides by adjusting the plate dimensions, do you know how would you check the bending moment capacity of that weld connection there?

1) Work out the moment capacity that you wish to have at the joint.

2) Calculate the Sx of the weld group treating the welds as line elements.

3) Max weld stress = M/Sx.

4) Bump that up by a factor of 1.25 to account for this being rough science. This is a KootK factor, not a mandatory code thing.

5) Compare weld demand per millimetre with weld capacities per millimetre from your CISC steel manual.

6) Specify a minimum 5/16" fillet weld all around as there's little to be saved by going any smaller.

Check the weld section of your CISC manual to see if they have a canned table for this weld configuration. They probably do.

No doubt I screwed something up in there someplace. Not to worry, one of our steel experts will gladly school me in short order if that's the case.