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Precast Plank Welded to Angle at Side of Beam

Precast Plank Welded to Angle at Side of Beam

Precast Plank Welded to Angle at Side of Beam

(OP)
Yesterday, I posted a thread entitled: "Do You Trust Precast Weld-Plate To Laterally Support The Beam". Refer to that if necessary.

- If the precast plank bears into the side of the beam and is welded to an angle, which is welded to the web, the precast plank would not be welded to the compression flange.
- Can i still consider the welded precast plank to provide lateral bracing to the compression flange?
- Considering the typical staggering of precast weld-plates, if i CAN consider the beam to be braced, should i consider unbraced length based on only one side of the weld-plate spacings, or can i use both sides to reduce the unbraced length?
- I do not consider that concrete topping can provide a sufficient brace, if at all, to the compression flange of the beam. Agree or disagree?

Any other thoughts?

Thank you!

RE: Precast Plank Welded to Angle at Side of Beam

So you have a diaphragm connecting to the web of a supporting beam (details are always welcome). Typically, if I have a lateral reaction within 1/3 of the beam height from the compression flange (1/3 from the top), I say it's good to go. Otherwise, I need to argue that the connection restrains the beam from rotating (a big no-no for a single horizontal weld). This being said, it makes sense to provide a small return on the welds to prevent unzipping even if you are close to the compression flange. Make the angle yield before the weld fails under lateral loading.

Restated Question - Can you consider this lateral brace to act in compression and tension? Non-Answer - Why wouldn't you?

Restated question - Can you consider CIP topping as bracing the compression flange? Answer - Shear friction between the flange and the concrete is zero unless you provide studs. If the beam needs to rotate into the topping for lateral buckling, why wouldn't you consider that topping as bracing that beam against that rotation?

RE: Precast Plank Welded to Angle at Side of Beam

(OP)


I do not have a diaphragm and there is no lateral reaction.

I am simply designing some long-span beams that i would like to reduce the size of through providing a lower unbraced length of compression flange.

Although I've been doing this for years, i'm not convinced that i can reasonably consider the top flange as braced by either the this detail.

If the precast to steel weldment at 8' oc staggered, will NOT provide compression flange bracing, would the 3" of 4,000 psi concrete provide a sufficient brace?

RE: Precast Plank Welded to Angle at Side of Beam

If it's being cast into a topping slab, that's braced to me.

RE: Precast Plank Welded to Angle at Side of Beam

Agree that the welded connection, without additional review, does not provide the necessary lateral restraint against LTB. However, the topping will resist LTB in compression. If you had a pretopped system, you'd have to find another solution. But, with CIP topping, you are good to go.

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