Six Story Wood Frame Construction: Tips & Resources 7

[KootK]

I've got a number of projects in the works where six story wood construction, which is new to me, is being considered. They are all to be six stories of conventional wood (stick not timber) constructed above ground level transfer slabs. I'm seeking advice regarding this kind of construction as well as any published resources that may be available. Certainly, I'll be speaking with trade organizations such as the Canadian Wood Council. I'm hoping to jump start my knowledge quest, however, by requesting help from the crew here.

So far, I've got this from British Columbia's licensing body: Link

And for clever ideas, I have the following:

1) The dominant issues seem to be shrinkage, lateral load resistance, and wall construction at the heavily loaded lower floors.

2) Potentially, once could rotate the unit framing direction part way up the building with the goal of spreading the load, and some of the shrinkage around.

3) The height which brick is used ought to be limited to mitigate differential movement between brick and the doors and windows behind the joints.

4) Special detailing can be used for mechanical and electrical risers to mitigate the impacts of shrinkage on those systems.

Any other great ideas, articles, or manuals out there?

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[RFreund]

A couple questions on framing orientation and shrinkage:

There are typically two framing options - Spanning between exterior wall and corridor wall or Spanning between demising walls.

If spanning between exterior wall and corridor wall you could utilize top chord bearing to help eliminate shrinkage related to the rim joist, right? At the walls parallel to the trusses you would just have extra top plates that equals the thickness of the top chord of the truss right?

If spanning between demising walls - Options: 1.) In order to align trusses, have one truss bottom chord bearing and the other truss top chord bearing (on top of other truss), 2.) stagger the trusses, 3) Provide hangers on one side of the wall and top chord bear the other side trusses. If you use option 1.) then you would have a rim joist with potential shrinkage, although I like Mike's solution mentioned above.

I'm I thinking about this correctly?


EIT

http://www.HowToEngineer.com

 

[jayrod12]

I don't know if the argument for less shrinkage due to top chord bearing vs bottom chord.

Top chord bearing blocks are usually made up of stacked lumber from what I've seen, the orientation generally promotes more shrinkage as it's perpendicular to grain as opposed to parallel to grain. The last web of a bottom chord bearing truss will see minimal shrinkage axially, and then normally only has the chords in perpendicular to grain orientation.

Therefore my argument is the shrinkage difference between top chord and bottom chord bearing wood trusses is neglible and I suspect depending on the depth of the top chord bearing block, the bottom chord bearing may result in less shrinkage.

That being said, I've normally done top chord bearing in that situation (albeit I haven't done wood taller than 3 storeys). That way the corridor joists can be 2x6s which is the same depth as the bearing block for the trusses under the suites. Then at the walls parallel to the trusses I provide a 2x6 rim joist and blocking to keep the bearing height the same all around. Another fun fact about 2x6 corridor joists, it provides a nice chase for mechanical and they just provide a dropped ceiling to match the u/s of trusses it ends up leaving almost an 18" deep for the entire width of the corridor.

Wow, kinda went off on a tangent on that one.

 

[medeek]

Wow that elevator shaft is some crazy framing, nice picture. I'm not really familiar with tall wood structures but it would seem that steel would be the more economical solution for buildings over 4 stories tall.

A confused student is a good student.
Nathaniel P. Wilkerson, PE

http://www.medeek.com