Force Transfer Around Openings

[structeng13]

I have checked all the previous threads regarding the force transfer around openings approach that is specified in the the CBC2007 and I still have one question. Can this approach be used if the opening is a door rather than a window, assuming that holdowns are located only at the ends of the entire wall. I believe this issue was brought up, but nobody had an answer for it.

If you look at the figure 2304.3.5(b), it appears that the force transfer method may be used with a door opening becuase it is shown at the middle floor of the building.

It would seem that if a holdown was required at each side of the door, then the approach would simply turn into the segmented wall approach.

Thanks for your help!!

 

[Engineerataltitude]

The figure you are referencing is actually Fig. 2305.3.5(b).

I think you are reading too much into the location of that door in the schematic. The wall pier height next to the door is defined by it's relation to the horizontal diaphragm below and the height of the door. That would be the case, no matter what story the door was in.

Yes, you are right, you may look at the segments of that wall in the middle story as shear piers if you add force tranfer elements at the upper corners of the door and at all corners of the window. Then in your overturn analysis, you only have to look at uplift at the corners of the wall at that level.

If you used the segmented shear wall approach in that same wall, the only wall which looks like it would meet the height to width ratio is the section next to the door. The only location for holdowns (if needed) would not be on either side of the door, but on each side of that shear wall segment.

Take a look at the APA website though. They have a really good document called Whole House Wall Bracing which our local Building Department (in CA) accepts that provides defendable rationale for using much narrower shear wall segments than CBC2007 allows. Really helps some designs.

 

[structeng13]

Thanks for the response!! Just one more question, This is assuming that there is a diaphram below, in the case where the doors are on the first floor with the concrete foundation below, would you still apply the same methodology you describe in the last post? This has been asked a few times in previous posts and was never really answered.

Thanks!

 

[Engineerataltitude]

I'm assuming the door is at a height where you would step through the door onto an interior floor of some kind. The key for shear walls is that they are the vertical connectors for loads coming through horizontal diaphragms, then down to a foundation. Even if the first floor has cripple walls below it to foundation stem walls, the shear wall segment next to the door is only from horizontal diaphrgm above to the horizontal diaphragm below it.