Cover Plate Thickness

[umrce]

I recently had a fabricator request increasing a cover plate thickness, here are the parameters of the situation.

Flange thickness = 1.34"
Cover Plate thickness = 1.5"
Requested CP Thickness by contractor = 1.75"

Normally I wouldn't hesitate to approve the request but AASHTO LRFD limits the C.P. thickness to twice the flange thickness which their request would violate. It's not over by much but I'm curious, does anyone know why this limitation exists? There's no discussion in the commentary and if I could understand the limitation a little better, I think I could be OK with the change.

 

[bridgebuster]

Maybe I'm missing something but 1.75 is less than 2 times 1.34 (assuming one flange is 1.34" thick).

Off the top of my head the thickness limitation could be a fatigue concern.

 

[BridgeEI]

I believe bridgebuster is correct. I don't have the code in front of me, but you may look at the fatigue category details. I imagine it's in a low stress range.

 

[umrce]

Yes the 1.34 value is incorrect. Typo on my part.

 

[OSUCivlEng]

I didn't know cover plates were still used for new construction. Was there some kind of girder depth restriction?

 

[umrce]

Yes. We have no choice but to provide a cover plate due to that very issue.