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Technical Information
 | Wood 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).
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| SEAOC 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.
 | Diaphragm
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. |
| Use 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. |
| Tilt 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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