Shim Plates

[Rich2001]

I am looking for a reference (AWS or AASHTO)that limits the number of shim plates that can be used to fill a gap. For exapmple; if I have a gap between two members that is 3/8" can I use two shim plates on 1/8" and another 1/4"



--------------+
//////////////|
//////////////| plate
--------------+---+
\\\\\\\\\\\\\\\\\\| 1/8" shim
------------------+----+
/\/\/\/\/\/\/\/\/\/\/\/|
\/\/\/\/\/\/\/\/\/\/\/\| 1/4" shim
-----------------------+-------
///////////////////////////////
/////////////////////////////// beam flange
///////////////////////////////
-------------------------------



Vita sine litteris mors est.

 

[Bagman2524]

AISC ASD section J6 is a section on fillers. Fillers 1/4" or more thick must extend beyond the edges of the part. Fillers less than 1/4" must have its' edges flush and the connecting weld must be the sum of the weld size needed to carry the splice plate stress plus the thickness of the filler plate. It doesn't give any restrictions on number or size of fillers.

 

[Rich2001]

Thank you for the response.


I have a customer that stated that only one shim plate could be used in this connection, that is to say not stacked up (i.e 1/*" + 1/4" for a 3/8" shim). He stated that it is in AWS D1.5 or AASHTO. Though I do not remember ever reading this requirement, no one's memory is infallible. Hence, I posted the question to see if I missed something when I read those tomes.


Rich


Vita sine litteris mors est.

 

[HgTX]

I don't suppose you could ask your customer for a reference?

Bolted or welded filler plates?

For bolted plates, AASHTO LRFD 6.13.6.1.5 (I could look at the AASHTO standard provisions but they're up on a shelf and I'm too short to bother) says "Fillers 0.25 in. or more in thickness shall consist of not more than two plates, unless approved by the Engineer." That's about all it has to say about fillers. So it doesn't look like an AASHTO prohibition.

D1.5 is like what Bagman reports for AISC. You can use the 1/4" filler to transfer stress by welding it to the plate beneath it and welding the plate above it to it, but plates less than 1/4" can't be used to transfer stress; they're pure filler and the fillet weld in the lap needs to be increased in size just as if there were a gap there. Also recall that from 1/4" on up, your fillet must be at least 1/16" smaller than your plate.

So in the detail you show, you'd have a 3/16" weld from the shim edge to the flange, and then your 1/8" would be flush with the upper plate edge, not sticking out as you show, and then a 5/16" weld from the plate to the 1/4" shim, covering up the edge of the 1/8", for an effective throat of 3/16" as well (because you lose 1/8").

However, 3/16" violates D1.5 (and I think even AISC) minimum fillet weld sizes for any thickness of base metal. So if you actually want a 1/4" or 5/16" fillet-welded connection between your upper plate and your flange, you can't use two separate shims, but not exactly for the reason your customer states.

Hg

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