Need a book? Engineering books recommendations...

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

Re: Building Code Complexity

[Subject Prev][Subject Next][Thread Prev][Thread Next]
> From: "Sherman, William" <ShermanWC(--nospam--at)cdm.com>

> This email is submitted for general comments on building code complexity.
> (Comments on specific code requirements are also welcome.) 

I think that one of the things that you have encountered is really
related to the complexity of the structure that you are proposing. It
would also be practical to reduce the number of load cases to probable
controlling conditions.

> I have been developing design requirements for a single story pre-engineered
> metal building for a water treatment plant in New England. The structure is

> willing to pay for a preliminary design, legal counsel has said that if we
> pay a supplier for a design, that supplier should be excluded from bidding
> as they would have a competitive advantage over other bidders (for a public
> works project). Thus we plan to develop our own preliminary design to get
> foundation reactions. 

You are in a bit of a pickle if you can't obtain assistance from the
manufacturers. Maybe, you could pay all that are on the bid list for
preliminary reactions. That should be a one day turnaround to get budget
level - preliminary - information. Nobody comes out ahead.

> Developing the required design load cases has been a lesson in building code
> complexity. The governing building code is the 2000 IBC. The building is an
> L-shaped building and will have non-symmetrical bracing and irregular bay
> sizes, due to equipment layout. I have currently come up with a "minimum" of
> 83 load cases to be evaluated! (I guess I can understand why the building
> manufacturers no longer want to design for free.) 

> Due to the L-shaped building, plan irregularities must be accounted for in

Why are the two sections of the L interacting? The metal building
company will want to isolate them.

I do this regularly. Don't waste your time doing all load cases.
Although there may be 83 realistic load cases, only about 5 will control
at various foundation locations. Ignore symmetric reversal cases.
Asymmetric reversals will be limited - add a comfort factor. As a
colleague used to say, "round up and double". There are quick ways to
bracket your solutions for upper and lower limits.

Let the metal building designer deal with the 83 (or more) cases. Their
software will auto-generate most of them with a few keystrokes. The
building may have 20 or 30 locations controlled by different
combinations compared to my estimated 5 for foundations.

The fact that we are burdened with increasing code complexity has more
to do with the accessibility of computer generated solutions, and the
minimal quality of general structural software, than with code writers
gone awry.

In order to obtain a full reaction table, with all possible maximum
responses and proving that you have considered all practical and
mandated load cases, you have to enter 83 possible cases. If you ignore
symmetry or quasi-symmetry, the computer will not recognize that
symmetry is meaningful in the data that it reports for reactions or for
member analysis. So, we must enter all load cases. Bad software, good
control.

We try to squeeze economy from advancing technology. We have computers;
computers can analyze vast amounts of information quickly; added load
cases are minimally extra data input; therefore, we have the ability to
optimize every member in a structure uniquely. The fabricator doesn't
care how many different pieces there are anymore since they just load
the steel into the CNC milling machine and let the computer do it's job
- there are minimal set-up premiums to pay for part changes. This makes
economic sense from a material perspective and a time perspective.

83 load cases is not the fault of the codes.

-- 
Paul Ransom, P. Eng.
Civil/Structural/Project/International
Burlington, Ontario, Canada
<mailto:ad026(--nospam--at)hwcn.org> <http://www.hwcn.org/~ad026/civil.html>

******* ****** ******* ******** ******* ******* ******* ***
*   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) or UnSubscribe, please go to:
*
*   http://www.seaint.org/sealist1.asp
*
*   Questions 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 
******* ****** ****** ****** ******* ****** ****** ********