5 story wood building

[Skicat]

We just got a new project, and it happens to be a 4 & 5 story wood apartment building. We've never designed a 5 story building and I've been tasked with researching the topic. Particularly, the lateral stability aspects of a 5 story wood structure. Can you point me somewhere? Thanks.

 

[RARWOOD]

Contact the Western Wood Products Association. In the past they published several case studies on four and five story buildings.

In Minnesota prior to 1990 there were probably over a dozen 4 story wood frame apartment buildings built in the Minneapolis area and at least one five story building.

For the last 13-14 years I have not been dealing with the code requirements for heights and area so I don't know what the current limits are.

There are several things you can do when designing this type of building. One is to run your floor joist parallel with the outside walls. This puts less weight on your bearing walls and more dead load on the shear walls pependicular to the outside walls. Most contractors do not want to do this instead they want to run long span floor trusses and dump all the load into the corridor and outside walls.

When roof and floor trusses are used at 24" o.c. place a stud at every truss location. 16" o.c. spacing can be used adding an extra stud every 4' of wall at the truss that doesn't line up with the 16" o.c. spacing.

To properly detail the building you must accurately calculate the wood shrinkage and if you are using brick veener you must also calculate the brick expansion.

Plate crushing often is a problem because in many areas of the US they use SPF studs for top plates. In the past when I have designed multstory wood framed buildings I specified that the bearing stress under the roof trusses was to be less than 425 psi. If you don't do that the truss designer will base his bearing on the bearing stress of his bottom chord which will probably be 625 psi or higher.