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RE: Use of WOOD: Single Family Housing Design

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Brian, you missed a very important point of my post. First, I specifically
stated that few wood frame structures fail. This is a given. The only
failures that occur happen due to collapsed cripple walls below the first
floor and those that are not properly anchored to a foundation.
However, if you should do a little research of the financial loss to
insurance companies, FEMA and homeowners from both structural deficiencies
and construction defects after any of the earthquakes in the last ten years
you would see that the problem is one of ecconomics rather than life safety.
With performance based rules applying to new codes we are recognizing the
need to protect the owners investment against damage. The potential home
buyer has every right to expect that his home will perform at the same level
as that of an engineered home. Conventional framed homes are neither as
stiff nor afforded the same level of attention during construction as
engineered homes and are therefore suseptible to greater levels of damage.
Unfortunately, no provision is made to disclose this to the owner and this
is where the problem lies.
If you don't believe this, contact the insurance industry and ask why we
must purchase our earthquake coverage from a state plan instead of the
number of insurance companies that existed before the Northridge earthquake.
Your comments about 75 year old homes are very similar to those made by
contractors and unknowledgeable laypersons. The answer is that the time
and/or conditions have not been right for damage to occur. The one true fact
is that when the conditions turn favorable for damage, the owner will be the
first to bitch about quality and demand a favorable return on his policy to
bring his poorly constructed home up to engineered code standards.

Here are the facts: The majority of homebuyers are lower and middle income
families. Virtually every person in this country resides in a wood framed
home. In California alone, over 2 million homes constructed prior to 1969
may have structural deficiencies in the form of lack of cripple wall bracing
to inadequate connection to their foundations. This does not include
multi-residential units that have similar deficiencies.
Homebuyers purchase as much as their income will afford them. In the first
five to ten years of their ownership, they scrimp and save to make the
mortgage payment. However, as their income rises, their mortgage (at a fixed
rate) stays constant and they find that they have more money for other
luxuries in life. After a major event like Northridge, owners had to decide
where the money was comming from to repair their damaged homes. Few had 15
or 20 thousand in the bank to cover their deductible (homes in the Venice
area of approximately 1200 square feet where well over be$200,000.00).
Without low income loans, FEMA money and insurance, few homeowners had the
resources to fix their homes. The rest of us pay for this either by taxation
or by increased insurance premiums. The average cost of a residential
retrofit is $2,500.00. The average deductible is around $15,000. Homes that
suffered cripple wall failures or slid off their foundations required
approximately $25,000.00 to repair - which might have been avoided with an
investment of less than 10% of the repair cost devoted to retrofit.

Your rather naive if you believe that a damaged home is not devastating to a
home owner. When the family is prevented from returning to their home due to
structural damage, they suffer as badly as those who are burglarized or
their homes damaged from fire. It's an intrusion of something that is your
haven and is your personal space. This is devastating to displaced families.

Could all of this been avoided - you bet. All it took was a small investment
in more hardware and better inspection practices to insure that the builder
understood how to construct a load path.

Here's one for you. Santa Monica made the same claim as your did about some
150 Unreinforced masonry buildings that existed in their town. They fought
the state mandatory identification of URM structures and refused to create a
mandatory retrofit ordinance until around 1993 (some ten years after the
city of Los Angeles started to retrofit based upon Division 68 standards).
Santa Monica argued that their buildings, many of which were close to 100
years old, were on an inactive fault and were never damaged in subsequent
earthquakes - including Whittier Narrows, Sierra Madre and all of those
prior to Northridge.
Owners who wished to obtain funding for retrofit work found that local banks
would not loan since there was a consensus that the work was not necessary
as the rest of the state thought it was. The ex-mayor who led the battle
against the state was an attorney and also a building owner in Santa Monica
who felt threatened by the state measure since Santa Monica was under strict
rent control (although owners could raise rents sufficiently to amortize the
cost of retrofit. They hired "Expert Witnesses" to testify as to the city's
special conditions - one was from a major University in Southern California.

Then along came the Northridge earthquake. The rest is history - over 100
URM buildings severely damaged, many (including one Automobile dealership)
totally destroyed to rubble.
I designed the retrofit on a beautiful Church at 7th and Arizona (I believe
it was the First Christian Church of Santa Monica) which offered homes for
the homeless. Before they could obtain funding the earthquake hit.
Fortunately, they retrofit the mezzanine and attic section of the building
and this saved at least eight lives. Once the people were out, the building
was demolished and now all that is left is the drawings of a beautiful
building that once existed and could have been saved.
The same holds true of the large commercial and office building located at
4th and Broadway in Santa Monica. I designed the retrofit but the owner (an
83 year old lady) could not find funding to do the work. After the
earthquake, her cost of repair added over $500,000.00 to the retrofit work.
Fortunately, here agent was the architect who occupied the building. He
returned the building to the way it looked in 1929 when it was built. The
retrofit work, for the most part, was concealed and the building survived.
The owner, however, will never recoup her financial loss in her lifetime.

My point is that your comments do not represent those of a knowlegable
engineer who deals in the repair of damaged buildings. It's not restricted
to areas of seismic activities. Consider the extent of damage that might
have been avoided in Florida and Texas due to hurricanes. Much of this
damage was due to poor construction quality. Do you blame the contractor who
was never tested nor needs to know what the provisions of the code requires.
Now, how is he to know if the buildings were never designed by professionals
whose job it is to know.

As far as your comments about Patio Covers: Conventional framing standards
are less stringent than engineered solutions - something that is the
opposite with any other materials in the code. We would not be arguing if
the code was written to standards that exceeded engineered solutions. This
includes Patio Covers. The thought is that this is a secondary type
structure and does not matter if it stays up or not. Tell that to the poor
sap who happens to be below it when it goes.

Funny, I just finished a commerical building. The building has a trellis
work attached to it. The architect wants to use two 6x6 posts and encase
them in a 2' wide stud and stucco encasement. I designed the post as a steel
tube considering that the post will not really be seen inasmuch as it is
encased. The architect called me on this - rather angry. He stated that the
building department would allow a 6x6 as long as I provided the calculations
to show that the 24" x 10'-0" wide encasment could handle the shear. I
really hate this argument. The fact is that the city will accept anything
the engineer is willing to take responsibility for unless the building plan
checker is sharp enought to see that it won't work. They tell this to the
contractors all the time (probably to get rid of them that much faster) and
this passes the responsibility to the engineer to defend his design. When it
does not match what he wants, the most common response is "All I need is for
you to do a short calc to show that it works and the building offical will
accept it". And it's these same architects that would rather provide their
own engineering to save a few bucks.
Now for the reality check: the trellis consists of 4x12 beams at 24" on
center above two 6x16 rough sawn beams. The depth is 18' and the width is
18'. There are two columns supporting one end and the other is attached to
the building.
The weight is pretty large for this "trellis".
I suggested to the architect that he consider using a shorter tube steel
column connected to the foundation with a bolted moment connection to the
foundation. I told him to slip the 6x6 wood column into the steel and bolt
through. This provides sufficient rigidity so that the a moment connection
is created and if the column is ever damaged, it can be easily replaced. The
steel sleeve would not be seen since it was encased.
I also explained that since the 6x6 occurs in the middle of the 24" square
encasement and that the wall of the encasement does not meet H/b requrments
nor was it positivly connected to allow a shear transfer to occur.
The architect became rather indignant and told me that he has never seen a
structure like this collaps and that other engineers have simply provided
him a calculation to prove the 24" x 10' panels. Rather than tell him to
stamp this section off himself, I left it hanging until I get paid. Then
I'll tell him that if he want to save a few bucks, he can cloud in the
revision and provide his own stamp. I won't comprimise what I know is safe
to simply give him what he wants. Pity the poor schnook who is under his
"Trellis" when the conditions are right. (Being within 8 miles of the San
Andreas Fault it is almost a given that the conditions will be right and
soon).

Sorry to be so lengthy, but when you make a passing comment such as this,
you need to be educated. The simple answer to your assessment is that these
buildings have simply been lucky. Their time will come.

Dennis S. Wish PE