Level Difference due to shrinkage 1

[JohnRwals]

Hi!

When four or five story apartments are built with wood structure, CMU stairs or elevator shafts are often built first.
I wonder how constructors adjust the difference between finish levels when wood structure and CMU wall do not match.
How much accurately can the shrinkage of wood frames be predictable/calculated?
I guess it is not easy to calculate and control wood shrinkage because it's a natural product.

Thanks!

JRW

 

[rowingengineer]

In the structures due to compression and drying you have to predict the settlement for want of a better word. Most manufactures provide sufficient information to undertake the analysis, as often you are using a laminate of some description.

 

[r13]

I am not a wood guy, but wouldn't shrinkage be a significant matter after a period of time, not in the rather short construction period? I think precaution should be taken when you detailing the flooring though.

 

[Celt83]

WoodWorks wrote up a pretty decent report on accommodating shrinkage: Link

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[Celt83]

In my experience the shrinkage is very real and tend to see cracking in interior finishes at stair and elevator cores where the metal door frame bridges across the masonry and the isolating furring wall.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer

 

[milkshakelake]

I'd say this is the main problem with wood structures. Contractors and developers want to use CMU stair and elevator cores, but they won't shrink whereas the rest of the structure will. I always try to use wood stair/elevator cores so the shrinkage is the same throughout the structure but nobody wants to do it that way.

 

[JohnRwals]

As hybrid construction will more popular, this problem will happen more frequently.
In fact, I am having this problem in the precast parking structures surrounded with wood structure apartment units.
Whenever this happened, I saw precast walls trimmed.
Also, as this problem happens frequently, I think architects should recognize and try to solve this issue in the design stage.

But, how can we, Structural Engineers, solve/avoid this problem?
I wonder how wood structure engineers handle this issue.

JRW

 

[Celt83]

really the best we can do is provide the Architect/Envelope consultant estimates on the relative movements between the wood structure and adjacent masonry or pre-cast structures. The detailing of the joint falls into their court. I've seen joint covers similar to this, Link, used at passageways which rotates with the side that shrinks.

I have less concern with the passageways vs things like brick veneers which are getting used all over these relatively new 5-story wood buildings. The joint detailing seems to still very much be in it's infancy so get a lot of shocked pikachu faces when I let folks know the anticipated differential movement can be in the range of 1 5/8" to 2" at the upper levels.

My Personal Open Source Structural Applications:

https://github.com/buddyd16/Structural-Engineering

Open Source Structural GitHub Group:

https://github.com/open-struct-engineer