Slide Plate Base Plate Design

[jyokley]

Hello all,

I am trying to implement a fluorogold (PFTE Teflon) slide bearing plate assembly at the base plate connection of some steel beam members, to allow for unrestrained thermal expansion/contraction of the beam (pictured).

My questions are:

1) Does AISC Design Guide 1 still apply in this situation where there are two tack-welded sliding plates effectively sandwiched between two steel baseplates?
2) Am I allowed to consider these two outer base plates (let's say 1/2" thick) as effectively one 1" base plate for resisting bending forces?
3) Is it of any concern to have this weaker fluorogold material "going along for the ride" and deflecting with the bending of these outer steel plates, assuming the plates have sufficient bending capacity? The fluorogold material only has a tensile strength of 2 ksi compared to my 58 ksi base plates.

I appreciate any help, I'm a junior engineer and I haven't designed this type of connection before. Thanks!

 

[dik]

I've usually seen this done using 'keeper angles' to prevent 'liftoff'.

So strange to see the singularity approaching while the entire planet is rapidly turning into a hellscape. -John Coates

-Dik

 

[sbisteel]

1) Yes, as far as designing the plate as a cantilever element to distribute bearing stresses.
2) No, each plate is independent.
3) Bearing stresses should be limited to allow movement, the manufacturer should say somewhere what the maximum compressive stress is. This is where you start to determine the minimum contact area of the teflon plates, whatever that overlap is considering the maximum movement range.

 

[jyokley]

Thank you sbisteel,

In response to 2), I understand that each plate has its own bearing/bending capacity that is calculated independently. I suppose a better question is: Is the applied loading shared equally between the two base plates, for the purposes of determining the required base plate thickness for each?

In response to 3), I have the max compressive stress data available for the material, however if I am expecting flexural bending forces, wouldn't I also need to know the yield stress of the material? Or would it be better to instead have a small isolated slide plate at each anchor bolt so that it doesn't receive any flexural forces over the full length of the outer steel plates? (currently I have the fluorogold sliding plates matching the size of the steel plates)