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RE: Lateral load statistical basis

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Bob,

There is a committee in the ASCE / SEI called "Design Loads on Structures
During Construction" that is in the process of addressing this issue.  I'm
not sure how long it will take to produce something.

Once you've satisfied yourself that this is indeed a temporary structure,
you need to address the wind and seismic issues separately.  Statistically
you need to look at the chance of exceedance along with the design life.  It
is markedly different from wind to seismic.  You might want to look at mean
recurrence interval.

After some discussions with John Paterka of CPP, I decided to use a 1 year
wind as a minimum for temporary construction supports.  ASCE 7 has some
guidance in how to determine wind pressures.  

I would look at the FEMA 302 to determine what probability would make sense.
I would suspect that a higher mean recurrence interval would be appropriate
for seismic due to the nature of seismic design. 

Regards,
Harold Sprague

> -----Original Message-----
> From:	Bob Hanson [SMTP:Hansonb(--nospam--at)hilberteng.com]
> Sent:	Tuesday, January 25, 2000 12:37 PM
> To:	Seaosc List EMAILto (E-mail)
> Subject:	Lateral load statistical basis
> 
> List,
> I would like to get opinions on lateral loads on a structure that is going
> to exist for only 35 days. When one looks at our building codes the wind
> and
> seismic are based on a probability of occurrence. So is it to simplistic
> an
> approach to expect to be able adjust these loads when the structure exists
> for 35 days and not the statistical base. (50 years) If any information
> sources related to this exist I would be interested. The related project
> to
> this is removal of framing, structural retrofitting, remove and replace
> equipment, and restore structure. This is a equipment support structure
> and
> not a building. The equipment is tired and needs to be replaced. The
> structure is being retrofitted for a temporary condition and it seems that
> some adjustments to code lateral loads should be allowed in retrofits for
> a
> 35 day life structure. The local code for normal structures is 1998
> California building code, seismic zone 4 & 70 mph wind.
> Thanks in advance,
> Bob Hanson
>