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Re: Wind damaged residences in Kansas[Subject Prev][Subject Next][Thread Prev][Thread Next]
- To: seaint(--nospam--at)seaint.org
- Subject: Re: Wind damaged residences in Kansas
- From: Jim Kestner <jkestner(--nospam--at)somervilleinc.com>
- Date: Fri, 13 Nov 1998 16:23:12 -0600
- Cc: reachnet-l(--nospam--at)NAHBRC.ORG, "'William Nelson'" <BNelsonSE(--nospam--at)email.msn.com>
I would suggest involving the Insurance Underwriters in this process since we could use their influence in convincing regulators that something must be done.
I like the idea of using a presciptive code within certain limits, since it is much more practical to administer for this portion of the building industry. The toughest issue to solve on your list of suggestions is the tort reform.
Dennis S. Wish wrote:
"Times, they are a changin'" I believe that we will soon have a new avenue to address these problems on a combined effort with Architects, Engineers and Builders. Owners will believe the informed and educated building professionals that they trust in. As a profession, we are starting to see movement in the area of a unified effort to address these problems and, hopefully, correct them.
REACH (Residential Engineers and Architects Council on Building), SEA, ASCE's AEI and, I believe, SEI committees are all starting to look into wood construction issues and in a unified manner (see Rawn Nelson's message on the SEAint List).
I am trying very hard to help filter information from these organizations onto one platform - SEAint where the information can be retrieved in one easy location rather than hunted down on numerous servers. This also provides the tools needed to help each organization combine their efforts with independents who can offer even more to the knowledge that we need.
Just since this thread started, I see the first obstical - having the same information reach two separate lists. This is something that I believe can be resolved within SEAint with the help of REACH and other groups. I only takes a small effort to insure the assimilation of information.
FEMA's latest grant to CUREE - CALTECH is another major move that uses the damage from the Northridge earthquake to study the problems associated with wood framed design and construction.
Although required by the next adoption of the 97 UBC in my area, I am not personally convinced that the answer to reduced damage is stricter design measures (ie, rigid diaphram analysis for horizontal wood diaphragms historically considered flexible).
I believe that we can come to a meeting of the minds in order to resolve many of these issues by better coordination between Architect-Engineer and Builder. We also need better coordination standards in the field that building inspectors and officals can follow (especially in area's that do not adopt or enforce BOCA or UBC) for residential construction.
Jim, I think we are on the threshold of helping to solve these problems by having the cooperation of other professional organizations. Here are some suggestions that I have had on my mind and discussed with other in the past year or more:
I am sure that there are many other issues to raise and overcome, but these are some that I feel are most pressing. The ability to discuss them on the List and have those working in specific committees will gain more understanding of what occurs in practice and may be able to help resolve these issues. Sincerely,Dennis S. Wish PELa Quinta California
- Correct the ommissions and discontinuities that exist in Conventional Framing Code provisions and create a prescriptive model that non-professionals will find easy to understand
- Adopt Structural Observation requirments which can be performed by any inspector and/or professional with a proven understanding of load paths. Even if a professional is not required in the design of a conventionally framed structure, the owner should be responsible to hire an independent inspector to verify that all load path connections and compliance with Conventional framing standards are met in the field before finishes are attached to the home or commercial structure. As local building Inspectors become more specially trained, they may be able to adequatly make these observations in the field.
- Promote special education of Construction Framers. Inasmuch as gravity and lateral load path construction requires more understanding of proper connections required by Conventional Framing Standards, those involved with this work should be treated as specialists of construction and properly trained. This, I feel, would greatly reduce the types of damage that we have been seeing.
- Presently, Conventional Framing standards allow a licensed professional to design portions of the structure without taking responsiblity for the rest. In order for most professionals to accept this, there needs to be legal protection from potential liability. Presently, almost anyone associated with the structure of a building can be pulled into costly law suits as a Cross-Complaintent. This needs to be corrected in the courts so that those who are not responsible need not suffer financially from their involvment.
From: Jim Kestner [mailto:jkestner(--nospam--at)somervilleinc.com]
Sent: Friday, November 13, 1998 11:55 AM
Subject: Re: Wind damaged residences in Kansas
I agree with alot of what Harold said...............lack of
enforcement..............insurance companies willing to
pay...............inadequate load paths to the ground............lack of
required holddowns................etc. Engineering of the wood frame for houses
is not required by the local codes so it is typically left up to the contractor.
When we design wood frame commercial buildings, we inevitably get complaints of
overdesign from contractors, owners and architects who all believe "it is just a
big house"and therefore it should be built just like all the other houses. I
know of many structural engineers who refuse to work on wood frames because of
the hassle that we constantly face when we design it by the codes.
Unfortunately, poor performance of these houses during a moderate wind storm
confirms that something is wrong with what is being allowed, but it seems like
nothing changes. I hate to say it but, until the losses are big enough (like
Homestead, Florida during Hurricane Andrew) nothing will change. There is too
much momentum trying to keep things the same (we are fighting an uphill battle).
Any suggestions? Anyone who wants to take up this cause?
Jim Kestner, P.E.
Green Bay, Wi
Harold Sprague wrote:
> I consulted on many residences (new construction and forensics) in the
> Midwest where wind rules. Every time the wind exceeds 70 mph there is
> significant damage to residential structures. There are many reasons for
> this; all of which are because of poor design practices that are used
> because it is always done that way, and lax inspection. They are prone to
> tornadoes and micro bursts embedded in thunderstorms. As long as insurance
> covers it, and the inspectors don't push it, the home owners are reluctant
> to be proactive.
> The fragmentation of code authority is also of no help. Each small
> municipality has its own meager residential inspection department which
> accepts anything "because everyone else does it that way" and "if we do it
> differently, the developers will go elsewhere".
> When the houses get more expensive, the load paths get more complicated, and
> all structural design is done by the framer. The more expensive the house
> the less safe it is.
> The reasons for the failures are:
> 1. No load path for lateral wind forces and wind uplift. No hurricane
> clips or uplift straps.
> 2. Most all roof construction is 2 x 6's @ 24" with cripple walls as
> required. Any wall is fair game as a bearing wall.
> 3. No uplift details at the ridge or the cripple walls.
> 4. End nailing the sills into the studs (no uplift resistance).
> 5. The use of spaced 1 x's for roof sheathing (primarily in the Kansas City
> area). Residences of $150,000 or greater generally require a wood roof by
> local covenant.
> 6. Poor end wall details. The rim joist at the walls parallel to the
> ceiling and floor joists goes into cross grain bending. (Why do the walls
> squeak when the wind blows?)
> 7. Use of continuous headers over several windows. The continuous header
> goes into cross grain bending and torsion.
> 8. Poor nailing of the plywood shear walls at the corners.
> 9. Platform framing even at the "dramatic" 2 story entrance or vaulted
> ceiling. This creates a hinge at midspan of the studs, which pairs up
> nicely with the 2 other hinges at the top and bottom. (2 hinges - good; 3
> hinges bad)
> 10. Wall studs stay 2 x 4 @ 16" even spanning 17 feet or so. The
> indiscriminate use of #3 grade substituting for #2 grade.
> 11. Notches in structural elements at any place the plumbers, HVAC, or
> electricians want. The HVAC guys use a chain saw and cut openings any where
> they want without regard to load path. They create many hinges in one
> structural element.
> 12. The dry wall contractor's practice of cutting part way into a stud at
> mid span to "straighten it".
> 13. The only horizontal diaphragm in the ceiling is the gypsum board.
> Any deviation from these practices causes most builders great
> consternation. I did not even get into the poor concrete and foundation
> practices. Remember all of the new houses that self destructed as they slid
> down a creek bank. The fill was just dumped in. I have even seen this in
> commercial developments where the owner / developer fired the geotech
> because the tests came out bad. (This resulted in pin piles, grout
> injection, plumbing repairs, etc.)
> Since I moved to Colorado where the soil is expansive, high winds, and
> increasing seismicity (per 1997 NEHRP) I don't do much residential.
> Harold Sprague, P.E
> The Neenan Company
> harold.sprague(--nospam--at)neenan.com <mailto:harold.sprague(--nospam--at)neenan.com>
> -----Original Message-----
> From: Dennis S. Wish PE [mailto:wish(--nospam--at)cwia.com]
> Sent: Thursday, November 12, 1998 10:51 PM
> To: SEA International List
> Cc: REACH List
> Subject: Wind damaged residences in Kansas
> Our local news reported extensive damage in the Mid-west by heavy wind
> gusts. In particular, it showed wood framed residences destroyed by an 80
> mph wind in the state of Kansas.
> Can anyone provide additional information on the causes and contributions to
> this type of damage of residential structures?
> The design criteria for 80 and 90 mph winds are not uncommon code
> requirements in parts of California. I would assume they are more prevalent
> in the Midwest due to high exposure area's.
> Therefore, when a failure such as these described by local news is
> disclosed, I am concerned were the mode of failure occurs.
> If anyone has any additional information on residential damages in the
> recent severe weather across the United States, I would appreciate any
> Please Cc all posts to the distribution on the top of my email. This will be
> sent to the SEA International Listservice and the REACH Listservice where we
> can share in the discussions.
> Dennis S. Wish PE
> La Quinta, California
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