shim plates under structures 4

[StudB8]

Please anybody advice .. Are shim plates under structural steel should be galvanized?? .. as it`s required by my client and
i dont find any reference standard for such requirement ?

 

[madmantrapper]

Is the structural steel you are shimming galvanized?

 

[StudB8]

yes, its galvanized

 

[hetgen]

Its expensive to galvanize shim... you will have to pay a significant premium for galvanizing small flat pieces like shims, but if its your client requirement i guess you have to provide galvanized shims.

 

[StudB8]

totally appreciate your answer .. but my question is regardless my client requirements, is it required or recommended by any
international standard or code.
as i see that shim plates anyway will be embedded under grouting and not exposed to air and rust, and in my previous projects i`ve never used galvanized shims under galvanized structures.

 

[hokie66]

If the client requires it and is paying for it, the shims have to be galvanized. There is no standard or code that requires the structure itself to be galvanized, but it is just common sense that if the structure is galvanized, all the components should be galvanized. The base of columns, the anchor bolts, etc., is usually where corrosion starts, so that is not the place to skimp.

 

[StudB8]

hokie66, thx for ur valuable answer, but let me ask the question in a different way,

from metallurgical point of view .. "black steel in contact with galvanized steel embedded under grout" is there any probability to rust.

 

[SAIL3]

I would galvanize them...no guarantee that the grout will be uniform and completely sealing the area in question...anyway, as hokie pointed out, this is an area prone to corrosion...

 

[SlideRuleEra]

StudB8 - Shims are not totally embedded in grout. Of course they are surrounded by grout on the sides and top, but most likely, are sitting on a concrete base that has a cold joint with the grout. If water wicks in through the cold joint, and that can happen, there can be a corrosion issue with black steel shims.

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[IFRs]

Would stainless shims be less expensive?

 

[JStephen]

Can you cut galvanized sheet or bar into shims? That might satisfy the requirement without having to galvanize a bunch of little pieces.

 

[TDIengineer]

I don't think you want to galvanize the bar and then cut it as the ends would be exposed. The galvanized process is a coating is my understanding.

 

[StudB8]

Thank you all .. got the point.

 

[DST148]

std88>> If the intent of your OP is metal compatatibility to resist corrosion then.....
Ref: AISC Steel Const. Manual 13th Ed., Table 2-6 : If base metal is galvanized steel and fastener metal is steel or cast iron,
then the corrosion of the galvanized base metal is marginally increased by the fastener.

 

[ameyerrenke]

I've galvanized them in the past, just because I thought it a good practice. As JStephens suggested, Galv sheet metal up to 3/16" thick should be readily available, and depending your application, may be acceptable.

 

[SteelPE]

Hokie66,

A little off topic.... and this may be a matter of interpretation, but I seem to remember ASCE24 having some requirements for galvanizing steel structures exposed to flood conditions.

 

[cvg]

check the galvanic chart. carbon steel and galvanized (zinc) are some distance apart on the chart (300 - 400 millivolts) and zinc will tend to act as the anode. There may be some concentrated corrosion at the shim contact point. stainless steel will not improve this since it would be more noble than carbon steel.

 

[JStephen]

A quick check on Google turns up some ready-made galvanized shims, for what that is worth.

 

[TomDOT]

IFRs, you do NOT want stainless in contact with galvanized. It will chew up your galvanizing quite quickly - if your environment is corrosive enough to warrant galvanizing, anyway. I most often see this with stainless bolts on galvanized items. Nice little halo of corrosion around each of the fasteners.