Return to index: [Subject] [Thread] [Date] [Author]

Re: ASD Load Combinations

[Subject Prev][Subject Next][Thread Prev][Thread Next]
The reason we need L and E both in this case is for ordinary floor
loads, which may be there during an earth-quake. (May be a factor of
0.75L or something would be acceptable for this). It would be difficult
for all of us if the code differentiated between different live loads
and put a proper factor for each type under various combinations.  I
vote for keeping all live loads together, even if it means designing for
improbable events in some structures.

Bill Allen wrote:
Even if you can visualize an earthquake occurring during a re-roofing
job, I
have to ask:

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)
ALLEN DESIGNS
Consulting Structural Engineers
Laguna Niguel, CA
http://www.AllenDesigns.com
V (949) 365-5696
F (949) 249-2297


******* ****** ******* ******** ******* ******* ******* *** 
*   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 
******* ****** ****** ****** ******* ****** ****** ********