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UBC and Hurricanes - was FBC Standards

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Gary,

Where is your project? The UBC has never been a strong code with regard to hurricane requirements. The UBC has always been a primarily western states code, and hurricanes are simply not a factor here.

The few areas where I have used the UBC in a potential hurricane environment I have used ASCE 7 for wind requirements and added engineering judgment rather than rely on codified procedures in the UBC.

You specifically refer to soil conditions. Poor soil conditions will have no effect on the hurricane requirements, but rather will really only effect the foundation design directly. Seismic forces are created via relative motion imposed from the ground surface. Poor soils or different types of soil response can have a tremendous impact on the magnitude, severity, and period of the ground motion which in turn can have a corresponding effect on the seismic forces generated in the structure. Look at the recorded effect the deep alluvial soils had on the response during the Mexico City earthquake as an example; the earthquake motion traveled hundreds of miles and then changed up passing through the altered medium and caused severely amplified local ground motion, in many ways worse than the result at the actual epicenter.

Hurricane or wind effects in general are more dependent on the topography of the ground rather than the consistency. Additionally hurricane forces are not cyclic in the same manner as seismic forces. The forces may be really large, higher than seismic in some instances, but the manner and type of failure is radically different. This is why the discontinuous zone increases are so important.

The current thread is focused on the FBC, or Florida Building Code, where I would certainly expect hurricane related provisions.

Paul Feather PE, SE
www.SE-Solutions.net
pfeather(--nospam--at)SE-Solutions.net
----- Original Message ----- From: "Gary Hodgson & Associates" <ghodgson(--nospam--at)bellnet.ca>
To: <seaint(--nospam--at)seaint.org>
Sent: Thursday, July 21, 2005 4:35 AM
Subject: RE: FBC Standards


A question abt the UBC from a Canuck who has never
had to use until recently.  The seismic requirements
impose a higher lateral force when soil conditions
are poor.  Shouldn't there be some type of increase
for hurricane type forces?  I know there is a danger
of liquifaction in seismic events, but there seem to
be more hurricanes and lots of damage.  Just a
thought.
Gary

On 20 Jul 2005 at 6:54, John C. Jones wrote:

If that area gets a hit with a full force wind then it will really be
nasty.  Ivan did tremendous damage, but I think the winds were only
around 110 when it came ashore.  These storms seems to sit right off
the coast at about 140 and then just drop like crazy as they hit that
shallow water.  I'm mainly speaking to the MS/AL/NWFL shoreline.

I was in a mandatory evac for Dennis while attending an ACEC meeting
in Destin.  9 miles of travel in 2:15.  That was fun.

John


John Jones, PE, SE
Board Certified Structural Engineer
john(--nospam--at)struct-engr.com
Barnett * Jones * Wilson, LLC
Pell City & Tuscaloosa, Alabama

-----Original Message-----
From: Andrew Kester, P.E. [mailto:akester(--nospam--at)cfl.rr.com]
Sent: Tuesday, July 19, 2005 8:42 PM
To: seaint(--nospam--at)seaint.org
Subject: FBC Standards


After last year's canes that hit the FL panhandle, and after Dennis I
am sure too, there was media discussion on how that area had lobbied
hard to get the standards lowered when the FBC was being written. If
you look at a current wind map in the FBC it does not make sense. Pay
particular close to the Big Bend region, or the "arm-pit" on the Gulf
side (only a geographic description), and there are wind contour lines
that seem to bend a bit, and a big dashed line which means "EXCEPTION"
to the wind-borne debris requirements. This area also has some coastal
properties owned by Tallahassee politicians. Just my conspiracy
theory.......

The paper said those areas were literally paying the price for those
lowered standards. It would be nice to see insurance companies lobby
against the builders and politicians pushing through lower standards.
It would be a smart investment on their part.

Andrew Kester, PE
Lake Mary, FL





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