Beam at cast-ins 6

[Veer007]

Hello guys, Please refer to the snap below, which option actually seems correct as I'm worried about beam slopes at the end if I weld a beam and cast-ins?

Thanks in advance!!

 

[Celt83]

Good stuff Brad.

The rocker bar looks like a good option especially if you have a long span girder with decent expected end rotations.

Interesting to see the FEM stress decrease from the full length weld to the partial end weld, while leaving the distribution of stress similar.

I'm making a thing:

http://www.thestructuraltoolbox.com

(It's no Kootware and it will probably break but it's alive!)

 

[Veer007]

Thanks for the detailed info. guys and great effort! Brad

Thanks in advance!!

 

[Veer007]

So all you agree with rocker bar detail, right, to be clear

Thanks in advance!!

 

[KootK]

So all you agree with rocker bar detail, right, to be clear

That's probably too strong of a statement. Were I to try to sum up the group's feelings on that detail, it would be as follows:

1) In terms of performance, the rocker bar detail is probably no worse than the other details and may have advantages in some specific applications.

2) In general, there does not seem to be a high degree of concern for the traditional details where beam deflection is kept within typical limits.

 

[KootK]

@Brad805: thanks for the modeling effort. Inadvertently, it's helped to answer a question that I've wondered about for a while. I used to work with a guy who put the beam stiffener at the far end, always, because he felt that would "steer" the beam reaction to that location and prevent leading edge block/concrete spalling. It was a form of the stiffness attracts load argument, albeit probably an erroneous one. Clearly, in situations such as that shown below, it doesn't necessarily work out that way.

 

[dik]

I wouldn't think it would have any effect. With rotation, the reaction would occur near the front edge of the bearing plate. I like using a 'rocker bar', but only for long spans and deep members... just a quirk no real 'rhyme nor reason'... I generally use a couple of inches of fillet weld at the 'edge'.

It would be interesting to see the distribution with a couple of headed studs in the middle of the plate would be... maybe move the compressive stress in the wall closer to the centre rather than at the edge.

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

-Dik

 

[KootK]

Yeah, from a stiffness perspective, one really needs to think of the stiffener as a a cruciform or tee assembly in conjunction with the beam web. If the beam web were made of Jello, I'm sure it would work just fine.

 

[phamENG]

One benefit for putting it all the way at the end: field access for bolting if your connection calls for it on the flanges. Hopefully you're not close on your web crippling/buckling checks, though...

 

[KootK]

Mechanically, the most beneficial place for the stiffener is surely at the front edge, near the bearing reaction. It's hard to know how close is close enough in that respect. To some extent, I suppose that one could let the crippling and buckling occur at the leading edge, if it wants to, and then trust the reaction to then shift over to the stiffener.

The rear stiffener makes sense to me if the goal is just LTB stability.

 

[bones206]

Bearing plates are usually sized for uniform bearing pressure, but it’s clear that at a certain beam rotation that assumption is significantly overestimating the effective bearing area.

 

[KootK]

Done properly and with no regard for economy, I'm sure that these connections would benefit from the use of bearing pads similar to what is done in precast & bridge construction. Bearing the stiff and local directly on the brittle is usually some kind of problem.