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RE: Load combinations with 30% Wind

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Tarik,
Various industries have had conventions regarding adjustments in wind pressures or velocities that have seldom withstood scrutiny. The proper way of looking into this is to use a risk based study, but this is a lot of work. And it varies a lot with the type of structure within a petrochemical facility.

You will find guidance in the Commentary of the ASCE 7. Referring specifically to the ASCE 7-05, you will need to reference C-6.5 beginning on page 283. It will reference Table's C6-6 and C6-7 on page 318. You will note that you can present the probabilities in a number of ways. Most people look at the mean recurrence interval for exposure over a given time period.

I would recommend a lot of study in probabilities for environmental loads. It is easy to misinterpret. Also bear in mind that what is being modified are wind velocities not wind pressures. Pressure varies with the square of wind velocity.

You may also want to reference a paper by Boggs and Peterka, "Wind Speeds for Design of Temporary Structures", ASCE Structures Congress 1992.

http://www.cppwind.com/papers/structural/temporarystructures.pdf


Regards,
Harold Sprague





From: TBerair(--nospam--at)technip.com
Reply-To: <seaint(--nospam--at)seaint.org>
To: <seaint(--nospam--at)seaint.org>
Subject: RE: Load combinations with 30% Wind
Date: Tue, 5 Sep 2006 17:04:19 +0200

Bill,

I looked into ASCE-7, IBC, UBC-97 and even into "Wind Load and Achor Bolt
Design for Petrochemical Facilities" which is an ASCE 1998 publication,
but found nothing about the Testing, Maintenance or even Erection
conditions.



Tarik BERAIR, PE,
CIVIL ENGINEERING DEPARTMENT
TECHNIP France
PARIS-LA-DEFENSE
Tel: +33-(0)1-40-90-11-13
Email: tberair(--nospam--at)technip.com







"Scott, William N." <William.Scott(--nospam--at)veco.com>
05/09/2006 16:53
Please respond to seaint

        To:     seaint(--nospam--at)seaint.org
        cc:
        Subject:        RE: Load combinations with 30% Wind


Try American Society of Civil Engineers ASCE-7 2005.

Bill


From: TBerair(--nospam--at)technip.com [mailto:TBerair(--nospam--at)technip.com]
Sent: Tuesday, September 05, 2006 6:28 AM
To: seaint(--nospam--at)seaint.org
Subject: Load combinations with 30% Wind


Dear colleagues,

We have been used to consider only 30% of the Wind when establishing load
combinations for Abnormal Operating, Testing or Maintenance conditions (we
design mainly downstream petrochemical facilities). I am investigating the
origin of such an assumption in all US codes, but turned unsuccessful.
Does anyone know a code that is mentioning this or any Load Combination
for Testing or Maintenance?

Regards

Tarik BERAIR, PE,
CIVIL ENGINEERING DEPARTMENT
TECHNIP France
PARIS-LA-DEFENSE
Tel: +33-(0)1-40-90-11-13
Email: tberair(--nospam--at)technip.com


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