Expansion Joints In Multi-Story Wood-Framed Buildings 3

[abusementpark]

Are there any accepted rules and guidelines for expansion joint requirements in multi-story wood-framed buildings (for example a 5 on 2 podium)? I haven't found much on this.

These types of buildings can have plan dimensions that are several hundred feet in overall length, with lots of irregular U and L shapes. However, in looking at other plans for these type of buildings, I don't often see expansion joints specified.

 

[r13]

From a review of thermal expansion coefficient of materials, it was noticed that the coefficient for wood is quite close to the brick and clay tile. Maybe you shall look into requirement for brick structures (note, I don't think the brick meant CMU though).

 

[JAE]

abusementpartk,
I don't think there are "rules" per se but generally we try to keep buildings in the 200 to 300 ft. maximum length range simply because....

Other reasons:
1. You may need to have various demising walls to limit area for fire protection requirements. Using a double CMU demising wall is a typical type of system and automatically introduces an EJ into the building.
2. Seismic considerations may suggest joint locations to break up your building into "regular" structures - vs. irregular classified structures - simplifying the seismic design.
3. Concerns over global foundation movements - breaking up a building into parts may help minimize effects of settlements...not sure a 200 ft. length does that but could help locally.

 

[jayrod12]

I would say that JAE's point number 1 is the most common reason I've seen.

 

[phamENG]

I have a related question. Say you're doing a 5 on 2 U shape and need to split it into 3 rectangles for seismic 'regularity' considerations. A 5 story wood building is pretty flexible - how do you handle the amplified seismic separations? I could see the required joint width getting pretty big.

 

[molibden]

Simple. Use CLT No, seriously, is this common to split buildings in regular parts? In my area architects would go crazy with all building envelope problems this causes.

 

[Aesur]

@phamENG - the key here from a seismic separation distance is don't rely on the allowed story drift, calculate the real story drift to minimize the required offset. I would suspect with adequate shear walls the actual deflections would be significantly less than allowable and you wouldn't see these large separations. We encountered this on a project a few years ago where we ended up with I believe 6" separation at the fire walls for a 4 or 5 story building. The detailing was unique (mainly from a firewall perspective though) and at the hallways you use expansion joint covers similar to: Link.

 

[phamENG]

Thanks, Aesur. That's a pretty slick joint cover.

 

[abusementpark]

I don't think there are "rules" per se but generally we try to keep buildings in the 200 to 300 ft. maximum length range simply because....

JAE - we are basically right at the 300' overall mark in both directions. It is in a low seismic zone (SDC B), but does have irregular shapes. As of right now, the architect isn't requiring any joints. So, I'm debating whether I need to force the issue with a structural expansion joint.

 

[Aesur]

I was going through our technical references and stumbled upon "Expansion Joints in Buildings" Technical report #65. Thought this may be useful information for this thread.

Although this technical report is older, it is still referenced in newer publications: Link

Here is a link to the technical report (please note it's free to download): Link

 

[abusementpark]

https://www.woodworks.org/experttip...imensional movement with temperature changes.

See the above link from Woodworks which seems to suggest that permanent expansion joints are not required, but temporary joints should be considered during construction.