Just a short note to all list members (Residential List);
For those of you who are on the SEAINT List this may not be news.
Beginning around the first week of April we will be entering into
discussions on this forum regarding design methodology for light-frame
wood construction. The reason for the wait is that I would like the
number of subscribers to increase so that the discussion can continue in
real-time rather than to expect new participants to access the archives
in order to catch up.
I have been involved in discussions with professionals who are writing
commercial and proprietary software and are currently at a stall over
issues that have not been resolved so as to create some form of standard
of professional practice. For software developers, this means sticking
their neck out and possibly becoming the first one to have it chopped
off short by either an expert witness with an opposing opinion, or more
likely by the lack of software sales. Some of the issues that I would
like to discuss (and please wait about one week before we formally begin
this discussion) include:
1. The design methods for buildings with non-orthogonal shearwalls or
with skewed geometry.
2. Is full-compliance design per the 97 UBC or 2000+ IBC for non-rigid
diaphragms practical? This asks the question as to how future owners of
homes designed by rotational analysis or in combination with worst-case
tributary methods will be able to remodel or make modifications to homes
when the original design drawings and analysis are no longer accessible.
2a.Design methods using an Envelope solution (combination of worst case
flexible and rigid results) verses Rigid Analysis
2b. Potential for creating a soft-story when designing for a diaphragm
assumed only rigid.
3. How are most offices treating inherent redundancies from interior
partitions when calculating Rho? You may wish to review the documents
located on the Structuralist.Net written by Gary Searer, SE that was
submitted to the SEAOC Seismology Committee that identifies the
inadequacy of the Rho calculations in various geometric structures.
4. Are engineers designing to less demanding methods such as the UBC
Simplified Static Methods design when the code requires stricter
compliance to both tributary and rigid diaphragm analysis?
5. Is full-compliance design in high risk regions creating opportunities
for compliance to prescriptive standards and are these
counter-productive to the intent to improve performance of residential
6. Should Conventional Construction provisions be changed to create a
level design field so that prescriptive methods method is no less
restrictive than the minimum full-compliance methods? Is this a
consideration that should be determined by regions of higher risk or
applicable to all regions within the code jurisdiction that is subject
to wind or seismic considerations?
7. Many engineers located in the Midwest and East coast argue that they
do not consider lateral design because they are located in regions of
low risk to seismic activity. However, this has been a strange argument
as all homes are affected by the worst case condition where wind or
seismic governs. The only exception that I can think of to this rule is
in regions where bearing walls are wood stud, but the home is sheathed
in brick (such as is common in large metropolitan cities). I think that
most engineers believe that seismic governs the design of single family
residences in high risk regions when, in fact, wind is typically the
governing factor (although we do tend to compare wind to seismic and
apply the worst case to each resisting line of shear). The question
then becomes; how do engineers avoid designing single family
light-framed residences subject to wind loads?
8. What tools are you using to design gravity and lateral loads to
multi-story wood framed structures (including cold-form or light-gauge
9. How many of you are creating proprietary spreadsheets or other
programs to design lateral distribution?
10. What software tools do we need for residential design and what are
the deficiencies of the software currently available? This is not
intended to denounce any commercial or free software but to provide
important evaluations from practicing professionals needed to improve
the tools that are available to us.
These are just a few of the questions I wish to discuss. However, I
would also like to solicit topics for discussion by practicing
professionals that I have not covered. What are the advantages or
disadvantages to full-compliance design that you must address? What
issues are you resolving by professional opinion rather than by guidance
from resources such as the ICBO Seismic Design Manual's (Volume II
Please take a few minutes to submit a list of the most important issues
that face you in the design of residential structures and we will open
these up for discussion.
Finally, I intend to post the threads from this discussion on The
Structuralist.Net Bulletin Board discussion forum rather than to
restrict access to searching the archives. By doing this, we will,
hopefully, be seeking input from those who are not interested in
subscribing to a Listservice but who may be willing to participate at
Please submit your list of open issues that need resolution before next
week (although you can bring this up at any time). This will be the time
when most developers will be paying particular attention.
Thanks to all for your participation,
Dennis S. Wish, PE
California Professional Engineer
The Structuralist.Net Information Infrastructure
You must subscribe to the Residential List to participate. You may do so
by visiting The Structuralist.Net Residential Listservice webpage at:
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