Technical Information

  bulletWood Shear Wall Deflections
Much has been said and written about shear wall deflections and now, more than ever, wood shear wall deflections are very critical even for the most nominal of shear loads. I have put together a sample calculation based on a fairly nominal shear wall based on 3/8" CDX plywood with 8d nails at 3". I calculated the shear wall deflection based on the panel capacity (490 PLF) using Simpson HD5A hold downs. Based on the UBC "four term" shear wall deflection equation, this assembly does not meet the deflection criteria of the 1997 UBC even though the panel meets the height to width ratio requirement of 2:1! To see the calculations in detail, click here. So, be careful when designing your shear walls and especially when selecting the hold downs (hint: try using PHDs instead of HDAs).
bulletSEAOC Position Papers
Thought engineering was "black and white"? Not when it comes to building codes. Fortunately, the Structural Engineers Association of California (SEAOC) has developed position papers on a few controversial subjects. bulletDiaphragm Rigidity Assumptions for Light Framed Wood Construction
For many years, structural engineers have designed and detailed wood framed buildings based on a "flexible diaphragm analysis". Although these buildings have generally performed well, some interpreting the code would have us wasting our time performing worthless calculations instead of spending it detailing load paths or performing structural observations. The above paper helps us to defend a more rational approach. bulletUse of Cantilevered Steel Columns in Residential Buildings in Lieu of Shear Walls
A strict interpretation of the 1997 UBC would have you using a R=2.2 for the entire building in one direction just because you had a single steel frame at the garage opening. Fortunately, SEAOC has stepped forward to help put some common sense back into structural design. bulletTilt Wall Connection to Footings
In some areas of the U.S., tilt wall panels are not positively connected to the footings. Read how this is not a good idea in high seismic regions.

For more information visit the SEAOC Websites:
SEAOC
SEAINT

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