Is Sliding Allowed per IBC?
Is Sliding Allowed per IBC?
(OP)
Have had some technical discussions with colleagues regarding the requirements in IBC regarding anchorage and sliding. Putting aside the argument of whether or not it is a great idea, does IBC preclude you from allowing a structure to slide? Section 1604.9 "Counteracting Structural Actions" says ".... where sliding is used to isolate the elements, the effects of friction between sliding elements shall be included as a force". Where reference is made to "elements", would that include between the structures base plate and foundation?
Since the question may come up, to be specific about the structure:
It falls under ASCE 7 Chapter 15 "Non-Building Structure Similar to a Building"
It is a multiple story (2 above ground) work platform with people working on it. Approx 16' to upper deck with a footprint of 20' x 30'.
Seismic Design Category D
Located indoors (manufacturing facility)
The coefficient of friction between steel base plates and concrete floor has been accounted for.
It has greater than 1.5 safety factor on tipping using ASCE 7 load combinations from Chapter 12 (ASD).
There is no concern for the structure impacting anything if it slides in an earthquake
It is not a temporary structure
So, the obvious question is "why would you NOT anchor it down", which is a legitimate question but again, putting that aside does the Code REQUIRE this structure to be anchored?
I would really appreciate how you all interpret the Code in this regard
Thanks,
TW
Since the question may come up, to be specific about the structure:
It falls under ASCE 7 Chapter 15 "Non-Building Structure Similar to a Building"
It is a multiple story (2 above ground) work platform with people working on it. Approx 16' to upper deck with a footprint of 20' x 30'.
Seismic Design Category D
Located indoors (manufacturing facility)
The coefficient of friction between steel base plates and concrete floor has been accounted for.
It has greater than 1.5 safety factor on tipping using ASCE 7 load combinations from Chapter 12 (ASD).
There is no concern for the structure impacting anything if it slides in an earthquake
It is not a temporary structure
So, the obvious question is "why would you NOT anchor it down", which is a legitimate question but again, putting that aside does the Code REQUIRE this structure to be anchored?
I would really appreciate how you all interpret the Code in this regard
Thanks,
TW






RE: Is Sliding Allowed per IBC?
Mike McCann, PE, SE (WA)
RE: Is Sliding Allowed per IBC?
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Is Sliding Allowed per IBC?
upward ground movement would restore the contact with the floor
in my experience riding out several earthquakes, you will have both horizontal and vertical ground movement depending on the type of wave. jumping and bouncing might be a worse consequence than sliding...
RE: Is Sliding Allowed per IBC?
I've seen it a few times with equipment in high seismic zones (or with thermal expansion issues): it sits on "slide plates". (While still being able to accommodate over turning forces.) Most commonly it's done with teflon plates. (I.e. a teflon plate epoxy bonded to a steel backing plate, and then that backing plate welded to structural steel/equipment support. (I.e. teflon on teflon) Teflon has a low coefficient of friction.)
Basically what I read that section of the code as saying is: you have to account for that (minimal friction) force in the supporting structure. (Like any other load path.)
RE: Is Sliding Allowed per IBC?
Even if the IBC does not address the anchorage to resist sliding, I think OSHA, and good engineering judgment does.
You can use friction in some structural situations as in shear friction, but I still use it sparingly as friction is an unreliable and variable force, sometimes not easily quantifiable.
Mike McCann, PE, SE (WA)
RE: Is Sliding Allowed per IBC?
I think a concern I'd have is the mezzanine sliding in some parts (some columns slip) while others do not and you have a strange set of forces in the columns that might be hard to predict.
This is similar to the requirement for building columns to have interconnected foundations to avoid the building doing the splits.
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RE: Is Sliding Allowed per IBC?
RE: Is Sliding Allowed per IBC?
TW
RE: Is Sliding Allowed per IBC?