Korolath Shims 1

[Bagman2524]

Does AISC-360 prohibit the use of non-steel shims, such as Korolath? My particular application is baseplates of small HSS columns.

All I know is P/A and Mc/I

 

[dik]

I don't know why they shouldn't... I've use a Fabreeka product to prevent cold transfer for bolted end plate connected cantilevers to interior building columns in Winnipeg.

Dik

 

[sbisteel]

I'm not aware of anything in the AISC specification that disallows compressible bearing materials for the steel to rest on. It's fairly common in the industry, either compressible materials or slide bearings such as teflon.

Within bolted connections the story is completely different. The funny thing about these thermal breaks is that both AISC and RCSC state specifically that the material within the bolt grip must be steel. I've asked them about these FRP plates and they've stated that this puts you outside the specification.

 

[dik]

I'm aware of that, but, have done it anyway... often more important to keep the cold out, and, I hate frost build-up inside a building... it drips.

Dik

 

[sbisteel]

Same here! Just a bit frustrating when the people writing the code have nothing to say about something that is becoming very common.

 

[canwesteng]

Don't the bolts transmit cold inside anyway?

 

[BridgeSmith]

Assuming the material for the thermal break within the grip of the bolts has at least the same modulus of elasticity as steel, and doesn't creep, it would seem the 'spirit' of the specifications would be met, and AISC just hasn't kept up. That said, I'm not sure if there are materials that would meet those criteria and provide enough insulation value to make a difference.

Rod Smith, P.E., The artist formerly known as HotRod10

 

[dik]

"Don't the bolts transmit cold inside anyway?"

Yes... but the small area compared to the area of the column/girt makes the effect minimal. An end plate attached to the column would transfer a lot of cold.

Dik

 

[dik]

"Assuming the material for the thermal break within the grip of the bolts has at least the same modulus of elasticity as steel, and doesn't creep,"

I used to use HDPE for the thermal break... but, came across the material from Fabreeka that has a much higher load capacity.

Dik

 

[dhengr]

Bagman2524:
Pay particular attention to such things as the modulus of elasticity, compressive strength, bearing strength, creep, etc. of the shim material. These are material properties that the supplier should have tested/proven and be willing to stand behind. Then, study the movements of the shim material due to the loads imposed upon it. If you can tolerate these movements, creep, compressive strain, etc., and what they do to the rest of the structure you should be o.k. Just as Dik and Sbisteel have suggested, and done. What ever happened to using a little engineering judgement, common sense and experience and applying these to design which is still within the intent of the bldg. codes. Every condition in the universe does not have its own code paragraph and blessing. What ever happened to the old, catch all code statement, ‘methods of design and construction shall comply with rational analysis, in accordance with well established principles of mechanics.’

 

[bob33]

Regarding heat transfer, stainless steel has about 1/3 the thermal conductivity of ordinary steel.

 

[dik]

I had one court case where the judge in his final summation commented about my 'cavalier application of the Ontario Building Code'...

Just a caution about stainless Steel... you don't want to use it if your exterior parts are HDG.

Dik