Structural expansion joints in bearing wall structures

[hsustersic]

Looking into the maximum length of a building before having to add an expansion joint. It looks like concrete and steel structures are very well-defined in this regard by AISC 360, Tech Report 65, and ACI 2243r-95/01, but I do not see equally clear references for bearing wall structures. The BIA Tek note 18-A appears to apply to brick veneer rather than load bearing CMU.

What is the recommended spacing of structural expansion joints in buildings constructed with:
CMU bearing walls
Cold formed metal bearing walls

Any thoughts?

Thanks.

 

[concretemasonry]

The BIA brick joint spacing does not necessarily apply because brick has a long term expansion, while concrete has a long term shrinkage.

For a CMU wall, go to the National Concrete Masonry Association (NCMA) ay ncma.org. On the upper right side of the home page there is square with a reference to TEK or tech notes (can remember exact terms). To log on to the TEK notes check a state (any state) and a producer (any producer) to get to the index and cost from the 100+ TEK notes the are well organized.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[rlflower]

In terms of cold-formed steel structures, the necessity of expansion joints in a long narrow structure would depend on factors such as the actual rigidity of the structure. A long narrow farm building built with cold-formed steel yet designed with inherent flexibilty (using cross-bracing for lateral stability) may not need expansion joints.

I to am interested in expansion joint requirements in cold-formed steel structures.

Richard L. Flower, P. E., LEED Green Associate
Senior Structural Engineer
Complere Engineering Group, Inc.

 

[hsustersic]

Thank you Dick - Based on NCMA Tek Note 10-02B that you mentioned, it looks like the regular CMU control joints spaced ~25ft are sufficient for CMU bearing walls to control expansion.

I was originally thinking about building expansion joints with double structure on each side of the joint - if you permit expansion at closer spaced control joints along the length of the building, as with masonry, I can see how one larger joint at a much larger spacing does not make sense. The control joints are also required for crack control, so letting them double as expansion joints is very logical.

Are there any references for Cold Formed Bearing Walls which discuss expansion joints? It would be nice if someone had a chart relating structure rigidity to expansion joint locations without having to calculate thermal expansion of each member and for each structure. I'm looking for a good rule of thumb.

 

[steellion]

As a rule of thumb, building expansion joints should be placed at 200 feet on center max. If you have a long, thin building, there are maximum aspect ratios that should be respected as far as BEJ placement, but the type of diaphragm is what controls the aspect ratio.

 

[hsustersic]

steellion - To what type of construction are you refering? We typically use a 300ft spacing for steel framed buildings in accordance with AISC and 200ft spacing for concrete buildings according to ACI/PCA.

 

[mijowe]

Assuming this is a one story building with brick bearing walls and a steel bar joist roof: It is the steel roof that is concern for the global building expansion joint, and therefore any recommendation that you would use in a steel building is applicable.