Bearing a Wide Flange Beam on Bearing Plate with 3/8" per Foot Slope 2

[Guastavino]

So I have a plain jane W10x22 beam to bear on two 12" load bearing masonry walls (on bearing plates). The beam slopes slightly, an 8" drop over 25', or a little under 3/8" per foot. I want about 6" of bearing on each end, which means that the gap will be ~3/16" on the high end of a truly level bearing plate. I'd prefer NOT to use a fabricated seat because it's expensive, but I also am willing to do that. I know I can get away with a 1/16" gap with fillet welds, but not a 3/16" gap.

1. Anyone encountered this with an economical solution?
2. Can I use tapered steel shims? I assume so, but I'm having trouble finding any that taper to these small dimensions that are tapered.
3. Any other ideas?

 

[BSVBD]

1. An SJI endorsed "New Millenium Buidling Systems" Steel Joist, Girder and Deck Guide says, "Sloped seats are not required for slopes less than 3/8":12.

2. Fill void with grout.

3. I've used flat-stock steel shims. Unless your reaction is unreasonable, your load should transfer safely through the end of beam itself assisted by 1-2 shims.

4. Use a series of round stock shims; each welded to bearing plate and or beam. I assume your beam will be either bolted or field welded to bearing plate or, in this case, shims. Fill in between shims with grout if necessary.

 

[KootK]

Imagine a detail like this:

1) Bearing plate w/studs etc as usual.
2) 2" W x 1/2" H x bf+2" long steel bar shop welded on top of bearing plate running perpendicular to beam.
3) Beam bears on steel bar and has web stiffeners that hopefully land on top of the bar.

Let me know if a sketch is required. Now you're down to less than a 1/16" gap. You only need the 6" bearing for the masonry, not the steel.

Alternately, perhaps the bearing plate could be post installed to sit upset from the masonry and be tilted with a grout bed below.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Guastavino]

Thanks much.

@KookK, I like your 2" bar idea (and don't need a sketch, it make perfect sense). I could use 2" of weld on each side of the beam which would give me 2 sides*2"*4 sixteenths*1.392k/sixteenth=22.3k of uplift capacity and this connection has plenty of bearing capacity. It also can allow me to center my load.

@BSVBD, I like those ideas, but I'm concerned with welding just on the back side of the beam. I guess I could put a 2" return on the edge of the flanges to make a "C"-shaped weld, because it takes 2" for the gap to equal a 1/16". Then I could fill that with grout. I just worry about the uplift case with the grout.

I'm probably overthinking this...but appreciate you all.

 

[BAretired]

Similar to KootK's idea but use a round bar instead of a square bar.

BA

 

[KootK]

I'm starting to like a single round bar too. It hadn't occurred to me that it could come shop welded to the beam.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[Guastavino]

How does single round bar work? Where's the connection to the base plate is what I'm getting at?

Thanks!

 

[KootK]

Flare bevel welds in pretty much the same locations as with my original detail.

How does one asses steel bearing for a round thing on a flat thing? Can't say that I've done that before.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[BAretired]

A half round is another option (flat side meeting base plate).

BA

 

[racookpe1978]

24 Dec 15 02:31
Flare bevel welds in pretty much the same locations as with my original detail.

How does one asses steel bearing for a round thing on a flat thing? Can't say that I've done that before.

1. First approximation: The round bar deflects and squishes slightly, so there is a finite width bearing on the flat plate (which also deforms slightly to create a rounded (dished or embedded) bearing area. Weight of the load on the round metal deforms plastically both the formerly round piece and the formerly flat piece.

2. more accurate. Assume a two-sided flare weld on both sides of the round bar. That fillet width is a defined bearing area onto the flat plate. Surface stress (which may or may not deform the flat plate) is the load divided by the area of the two fillets where they touch the flat plate.

 

[KootK]

@BA: how available/economical is a half round? Is cutting one from a solid round difficult? Are we still talking solid sections or small, circular HSS?

@racook:

Thanks for the advice.

Option #1. That's kinda what I had in mind. But what are the details, equations, and appropriate factors of safety etc? First principles stuff always sounds great right up until it's time to execute.

Option #2. This one would be complicated by residual stresses in the welds I imagine. Initially, I'd expect the welds to be in tension as a result of shrinkage restraint and the round to be essentially prestressed in compression. For that reason, I would favor a plastic solution like option 1.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[DaveAtkins]

I assume there will be shims BELOW the bearing plate, to allow for grout. Can they be used to make the bearing plate slope?

DaveAtkins

 

[structSU10]

I prefer the rocker bar arrangement per kootK - like you said above it allows for a much more concentric load on the base plate. I have always used flat bar stock for this, never thought to use round bar.

 

[BAretired]

@KootK,
I have used a round bar where I wanted to keep the beam clear of the bearing surface. Have never used a half round, but thought it may be a plausible solution. Could use a round bar with a small chord ground off to provide a flat surface against the base plate. The advantage of a round bar is that it ensures the bearing is directly over the centroid of the bar whereas a square bar tends to move the bearing to one of the corners.

I was thinking of solid sections but if a round HSS can be made to work, I see no reason why it should not be used.

BA

 

[BUGGAR]

We've also used segments of large O.D. pipe welded on as rockers. But this was a job with lots of large O.D. pipe (36"+).