Shrinkage of a wood bldg with steel beams and columns

[nuche1973]

Greetings all. I posted a question on supporting steel beams with wood columns and received some valuable insight on the subject, for which I am thankfull for. However, several weeks ago I attended a lucheon where the guest speaker stated in his lecture that the shrinkage issue between wood structures that have internal steel components was not an issue. This was due to the fact that the final structure was enclosed and minimal moisture was introduced into the building. This made sense, however, I am interested in seeing what you may think. FYI, the lecture was on wood structures, shear diaphragms and shear walls.

 

[jhoulette]

I suggest searching eng-tips prior to making new posts. Many common topics such as this have been discussed in the past.

search 'wood shrinkage' to find many posts about this topic but the one that provides a lot of information is

http://www.eng-tips.com/viewthread.cfm?qid=170708&page=6

You can mix rigid structural materials (steel, brick, concrete) with flexible materials (wood) as long as you are aware of the possible change in dimensions over time and allow for the movement to prevent failure.

Jim Houlette PE
Web:

http://www.evstudio.us

Online Magazine:

http://www.evstudio.info

 

[jhoulette]

I forgot to mention even working with similar materials you have to be aware of the change in dimensions.

Wood structures are sometimes poorly designed when an engineer does not take into consideration shrinkage is higher perpendicular to grain than parallel to grain.

Also, when designing log homes the engineer and the framer must detail and build the home to allow horizontal members to shrink while the vertical members (columns) will have minimal shrinkage. Adjustable column bases or caps are used to level to home after construction for the next couple years. Stairs are even built unlevel knowing they will move with the walls and become level after a couple years.


Jim Houlette PE
Web:

http://www.evstudio.us

Online Magazine:

http://www.evstudio.info

 

[dik]

I noted in the other thread that longitudinal shrinkage of wood is generally negligible.

Dik