Suspended Driveway Thermal Expansion

[YoungGunner]

Client informed us we were to design this suspended driveway for their fancy house. What you see here are the drawings provided by the fabricator. There will be 20 gauge corrugated steel with an 8" slab spanning between. The fabricator originally detailed all those connections to foundation walls for bolted plates to the foundation, the plates directly welded to the face of the steel girders. However, we thought about thermal expansion and became worried about it. I believe this would get between 1/4" to 5/16" change of length between seasons. The client is throwing a fit about not wanting to cut the existing retaining walls, which we originally wanted to do to have a bearing seat. Any thoughts on how to achieve thermal changes and still have vertical & lateral support without cutting the foundation?

 

[XR250]

Those beams seems a bit much for a residential driveway? Fire Truck access?
Honestly, with the proportions of those beams (14"x14"), do they need much attachment?

 

[jerseyshore]

I've done something similar on a house that overlooks midtown Manhattan, but below the driveway was a basement. I had to replace the entire driveway because water leaked in at the joint between edge of slab and wall and destroyed the steel beams (so keep that detail in mind for this).

I'm assuming this is entirely exposed since you have retaining walls on either side. I've used slotted connections to account for any horizontal movement anticipated where we couldn't use bearing plates.

 

[YoungGunner]

To add clarification, we didn't design the beams, this is just what the fabricator sent our way. They will be checked separately from the conversation on this thread.

I've used slotted connections to account for any horizontal movement anticipated where we couldn't use bearing plates.

I've seen on other threads on here that slotted holes shouldn't be used for thermal expansion, especially for outdoors where rust is an issue.

 

[jerseyshore]

For cyclical movement they generally aren't recommended, but your anticipated movement is very small.

An alternate detail is to create a seat on the side of the wall. I've used WT's or something similar to make a shelf. I didn't have to worry about horizontal movement, but don't see why you couldn't make it work with steel or maybe even teflon bearing plates.

 

[XR250]

Oh, now I get it, these are framed to the face of the wall.
I think JS has the right idea

 

[jerseyshore]

I like WTs because there are plenty of size options and the stiffeners are built in. Assuming your wall isn't really short, you can run them vertically for however long you need to space out the anchors.

 

[jayrod12]

Honestly, due to soil pressure these beams will be in a continual state of compression. The potential for minor shrinkage at the coldest temperatures wouldn't even cross my mind.