# Re: RE: Load Combinations for ASD 9th

• To: Bill(--nospam--at)allendesigns.com, seaint(--nospam--at)seaint.org
• Subject: Re: RE: Load Combinations for ASD 9th
• From: Rhkratzse(--nospam--at)aol.com
• Date: Tue, 22 Aug 2000 01:02:07 EDT
```Bill, I agree, but once in a while something like that happens, to wit:

What are the chances of a strong steady wind aligning perfectly with a narrow
inlet at low tide ... and sinking a floating bridge?  Well, it happened to
the Hood Canal Floating Bridge in Washington (state) twentysome years ago.
If any of those factors had not occurred "just right" the bridge would have
survived.  (The low tide was required to slack the lateral anchor cables to
allow sufficient movement to allow the waves, etc., etc.)  Very small
probability and I imagine the designers considered it practically impossible,
if they considered that combination at all.

Ralph Hueston Kratz, S.E.
Richmond CA USA

In a message dated 8/18/00 8:17:39 AM, Bill(--nospam--at)AllenDesigns.com writes:

<< Even if you can visualize an earthquake occurring during a re-roofing job,
I

What is the probability of THAT happening?

Isn't the design level earthquake something like 2% exceedance in 50 years?

A re-roof occurs every 10-20 years?

Are we talking about a 500-1,000 year event for a structure that won't last

50 years anyway?

Yes, it CAN happen. But, so can an engine falling off an airplane hitting a

roof. Are we going to design for THAT?

O.K., so my statistical analysis isn't accurate, but you get the idea.

IMO, combining wind OR earthquake load with roof live load (even 50% roof

live load) is pretty ridiculous.

Regards,

Bill Allen, S.E. (CA #2607) >>

******* ****** ******* ******** ******* ******* ******* ***
*   Read list FAQ at: http://www.seaint.org/list_FAQ.asp
*   This email was sent to you via Structural Engineers
*   Association of Southern California (SEAOSC) server. To
*   subscribe (no fee) to the list, send email to
*   admin(--nospam--at)seaint.org and in the body of the message type
*   "join seaint" (no quotes). To Unsubscribe, send email
*   to admin(--nospam--at)seaint.org and in the body of the message
*   type "leave seaint" (no quotes). For questions, send
*   email to seaint-ad(--nospam--at)seaint.org. Remember, any email you
*   send to the list is public domain and may be re-posted
*   without your permission. Make sure you visit our web
*   site at: http://www.seaint.org
******* ****** ****** ****** ******* ****** ****** ********

```