Cambering Steel Decks

[DougTheThug]

Hi all,

I'm looking to make a steel deck cambering jig so right now I'm trying to calculate the force required to permanently camber it a prescribed amount. What I've done so far is calculate the plastic force using [Plastic moment] = [Section Modulus]*[Yield Stress] and [Plastic Force] = (4*[Plastic Moment])/[Length between supports]. I should note that I am treating this as a simple supported member with the force applied directly in the centre. To get the section modulus, I summed the areas of the deck above and below the neutral plane multiplied by their respective distances from the neutral plane. [Section Mod] = SUM(A1*d1 + A2*d2). To find the necessary force to get a permanent camber, do I add this plastic force that I calculated to the force necessary to deflect the deck by the deflection I'm looking for (I'd be using the deflection equation for a simply supported beam). The cambering process would be cold. Let me know if anything is doesn't make sense or if you have any resources that I may benefit from looking over. Thanks.

 

[jayrod12]

My first question is why? I don't know if I've ever seen cambered deck before.

 

[ANE91]

This is one of those things that’s a lot easier to do by doing it, rather than by calcing it. Your calcs would have to account for plasticity of the full section, across the full range of span to be cambered, acknowledging that the ribbed deck will distort along the way and muck up your calcs, assuming consistent yield behavior at every point, factoring in the effect of load rate, and then add a bit more such that elastic recovery puts the deck where you want it.

Just put it on a rig and measure the forces with a gauge. VATech (and others) do it in-plane all the time.

Assuming this is for a school project or something.

 

[DougTheThug]

This is one of those things that’s a lot easier to do by doing it, rather than by calcing it. Your calcs would have to account for plasticity of the full section, across the full range of span to be cambered, acknowledging that the ribbed deck will distort along the way and muck up your calcs, assuming consistent yield behavior at every point, factoring in the effect of load rate, and then add a bit more such that elastic recovery puts the deck where you want it.

Just put it on a rig and measure the forces with a gauge. VATech (and others) do it in-plane all the time.

Assuming this is for a school project or something.

Do you think this would be a good method for approximating it though? I just want a ballpark value and would like to avoid sending it out for testing. I am not expecting to camber it a massive amount.

 

[271828]

Is it realistic to bend deck into the plastic range without local buckling?

I would've thought not.

 

[KootK]

Is it realistic to bend deck into the plastic range without local buckling?

I had the same concern but, as ANE91 intimated, there are fabricators out there doing it. I'm not sure if they are heat relieving the deck or what. Last sentence here for example. Even when I just bend deck to radius without plastifying it, I have some questions about how that impacts capacity. But we'll not let that stand in the way of architectural dreams.

 

[driftLimiter]

Its almost certain that the deck with experience instability prior to reaching the full plastic moment. There are a lot of places that are prone to local instability effects.

There are established procedure for bending metal deck along a curve that is parallel to the ribs. I would reach out to some fabricators and see what kind of feasibility and process they might have in place for bending these decks.