I am working on a freezer building where the columns are isolated from the foundation using a 6" insulating block. At lateral brace locations, in my case an x-brace, how is shear transferred through the block and into the foundation? If I consider the anchor rods in bending, the moment arm is too long and it leads to an excessive size and number of rods. Is there an alternate insulating pad that can be used that is thinner and yet provides protection for the footing?
Tek-Tips is the largest IT community on the Internet today!
Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!
-
Congratulations MintJulep on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!
Freezer Building X-Brace
- Thread starter vgc
- Start date
Vgc:
It’s been a very long time since I’ve been involved in the design of a freezer warehouse, so these are just some recollections of an older fellow, and maybe not the latest design/insulation details. Dik is right, you do usually need some heating system below the floor insulation, or you get some nasty freezing problems. Literally, an air flow tile system under the floor. Can you use a few more panels of x-bracing, so as to lower the shear at each column base, and stiffen the building frame? Can you weld a 3-4" sq. tube to the bottom of the base plate which extends down into the pier through the insulation block, just as the A.B’s. do? You have to pay some special attention to the lateral flexibility of these steel frame buildings, as this relates to the relative rigidity of the exterior insulation panels, or the panels will try to take the lateral loads. They act a vertical shear panels, and the joints btwn. the panels and at corners get abused, and don’t hold up. The panels can take the normal loads into the steel frame, but they should not be forced to rack w.r.t. each other. I’ve seen globs of ice on the exterior of these panel joints which you could chop off with an ax. In that case I was working for the panel manufacturer who was being blamed for the problem. You have to control the lateral frame deflection and connection details to manage this difference in stiffness. Most good insulated panel manufacturers have established details to manage this, listen to them.
It’s been a very long time since I’ve been involved in the design of a freezer warehouse, so these are just some recollections of an older fellow, and maybe not the latest design/insulation details. Dik is right, you do usually need some heating system below the floor insulation, or you get some nasty freezing problems. Literally, an air flow tile system under the floor. Can you use a few more panels of x-bracing, so as to lower the shear at each column base, and stiffen the building frame? Can you weld a 3-4" sq. tube to the bottom of the base plate which extends down into the pier through the insulation block, just as the A.B’s. do? You have to pay some special attention to the lateral flexibility of these steel frame buildings, as this relates to the relative rigidity of the exterior insulation panels, or the panels will try to take the lateral loads. They act a vertical shear panels, and the joints btwn. the panels and at corners get abused, and don’t hold up. The panels can take the normal loads into the steel frame, but they should not be forced to rack w.r.t. each other. I’ve seen globs of ice on the exterior of these panel joints which you could chop off with an ax. In that case I was working for the panel manufacturer who was being blamed for the problem. You have to control the lateral frame deflection and connection details to manage this difference in stiffness. Most good insulated panel manufacturers have established details to manage this, listen to them.
The 40,000 sq. ft. freezer building I am currently working on was built as coolers, but the owner has changed a few units to freezers. We simply removed & replaced the floor with a sand bed incorporating heating loops (the glycol is heated by the waste energy from the cooling), insulated on top of the sand & poured a new floor, and put complete freezer boxes inside the existing structure. We are currently doing a 10,000 sq. ft. cooler addition, but we have looked at the option of turning it into a freezer, & we have decided that the most satisfactory solution from a lot of points is an interior panel system. It avoids the problem of structure passing through the thermal envelope, among other things.
- Thread starter
- #6
Thank you for the replies. This particular buildings will have an underslab glycol heating system located in a 3" mud slab under the insulation and running over the footing. There still will be an insulating block .
Ishvaaag: I am not completely following your suggestion. I don't see how I get around the fact that I still have shear being applied to anchor rods 6" above where they project from the foundation.
dhengr: I am pretty much locked in to where the braces are.
The GC provided me with a detail they used on a prior job. In place of the block they used a 1" thick elastomeric bearing pad. I like that because I can get the anchors to work no problem. Is the 1" pad + the underslab heating enough to protect the cold from transferring into the footing? I am going to keep digging to find that answer.
Ishvaaag: I am not completely following your suggestion. I don't see how I get around the fact that I still have shear being applied to anchor rods 6" above where they project from the foundation.
dhengr: I am pretty much locked in to where the braces are.
The GC provided me with a detail they used on a prior job. In place of the block they used a 1" thick elastomeric bearing pad. I like that because I can get the anchors to work no problem. Is the 1" pad + the underslab heating enough to protect the cold from transferring into the footing? I am going to keep digging to find that answer.
- Status
Similar threads
- Question
- Question
- Question