Need a book? Engineering books recommendations...

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

RE: Direction of Seismic Loading

[Subject Prev][Subject Next][Thread Prev][Thread Next]

Tom,

 

I would use ASCE 7, Chapter 15 for the design of non-building structures. Non-building structures that are similar to buildings should consider orthogonal effects in the manner of Chapter 12.8.

 

A cylindrical non-building structure that has identical rigidity in all directions would see the worst effects from any earthquake regardless of direction. Earthquake effects are determined using Chapter 12.4 and 12.5.

 

 

Bill Scott, P.E., S.E., SECB
Civil/Structural TA
ConocoPhillips Alaska, Inc.
P.O. Box 100360
Anchorage, AK 99910
Wk 907-265-6062
Cell 907-952-6019

 

 

 

From: Tom.Hunt(--nospam--at)fluor.com [mailto:Tom.Hunt(--nospam--at)fluor.com]
Sent: Monday, February 14, 2011 2:31 PM
To: seaint(--nospam--at)seaint.org
Subject: Direction of Seismic Loading

 

Section 12.5 of ASCE 7-05 provides the requirements for the direction of application of seismic forces and for a typical rectangular building in California (SDC "D") I suspect most engineers would use 100% in one direction and 30% in the other to satisfy ASCE 7 Section 12.5.4.  My understanding is that this is to capture the effects of the earthquake forces at some direction other than the principal axis where the loading would impart some level of forces in both orthogonal force resisting systems at the same time.

I am having a discussion with a client who thinks the 100%-30% requirement would also apply to a single skirt support steel vertical vessel such as you would see in a petrochemical plant.  Since a vertical vessel is essentially a single symmetrical cantilever structure with a single lateral force resisting system, I would assume that ASCE 7 Section 12.5 would not apply.  That is, I would think you would just take 100% of the seismic load in any single direction.

Would you agree with this assumption?

Thanks,

Thomas Hunt, S.E.
Fluor------------------------------------------------------------
The information transmitted is intended only for the person
or entity to which it is addressed and may contain
proprietary, business-confidential and/or privileged material. 
If you are not the intended recipient of this message you are
hereby notified that any use, review, retransmission, dissemination,
distribution, reproduction or any action taken in reliance upon
this message is prohibited. If you received this in error, please
contact the sender and delete the material from any computer. 

Any views expressed in this message are those of the individual
sender and may not necessarily reflect the views of the company. 
------------------------------------------------------------