Structural Design Code/Standard question 2

[testrun]

Does a Structural Engineer have the right NOT to follow a PORTION of any given applicable Design Standard / Code (AASHTO for instance, in bridge design), if he doesn't want to (because it is very detailed and time consuming)?

I know that the Design Standards (AASHTO, ACI, ASD, IBC) aren't perfect, they can sometimes be very tedious, and that they can't possibly cover every single situation, so an engineer must use common sense and good judgment in using them. However, the thought that I'm getting at is that of: “The budget only allows for a certain amount of DEPTH of design, so I will do only as much as the budget affords (with no gross omissions of design), and then stamp the design and take ownership for it.”

 

[ACtrafficengr]

If a client skimps on the budget for design, I would expect their engineer to come up with a very crude, overdesigned structure which will cost more to construct than one that beneitted from more thought and effort in the design phase.

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[testrun]

Thanks ACtrafficengr. I ask because of the pressure I've received from senior engineers to simplify my designs, but in questionable ways, because of budget. It is one thing to simplify, it is another thing to over-simplify. Finding the balance is the hard part...

 

[jimaitken]

Testrun
I am assuming you are designing a bridge.
You should ask your client if this is acceptable to them first, if it is a DOT or FHWA, they are going to tell you "No!" in most cases, unless you have compelling reasons.

I would say that the engineer is responsible to ensure that their design is safe for use by the public. AASHTO, ACI, UBC, IBC, etc were all developed to ensure that minimum standards are met for design and construction, and for use of the structure by the public. If the reviewing agency (DOT, FHWA etc) requires that AASHTO be used for the design of THEIR bridge then the engineer MUST use that set of standards. The code is open to interpretation, but that does not relieve the engineer from their responsibility to the public.

As a structural engineer, "Tedious Calculations" should be your middle-name! Certain engineering tasks require "tedious" calculations to check all of the possible conditions the stucture may experience, regardless of the actual probability of occurence. The failure of your design will occur in the one condition you did NOT check! I sleep better at night knowing I checked all of those conditions.

I think you can make some conservative assumptions that may help you to make your design move faster as well as use computer programs to automate some of the design. There are plenty of proven computer programs available than can help you to reduce the the time needed and give you peace-of-mind that you have a sound design AND meet the code requirements.

If you still don't have time and budget I would say that you need to ask your client for more money, and if that is not an option put the project in the books as a loss, eat the extra cost and meet the code requirements anyway.

 

[jimaitken]

Testrun

I just saw your last post and want to add to my response.
Ask your senior engineers for guidence on how they would complete the design. They may be using their own experience and accepted practice at your DOT as background for their request. If they are still asking you to do something you are not comfortable with, tell them your feelings on the matter.

The amount of budget necessary for your extra effort to complete the design according to the code requirements will be a pittance compared with the money that it will cost you and your firm in claims, plans revisions, and potential legal costs if the design is faulty or a fialure occurs.

Good luck.

 

[bridgebuster]

You are obligated to a standard of care first and foremost, regardless of what it does to your budget. You have to follow whatever code is in your contract; any deviation needs to be agreed upon with your client.

A few years back, a client switched to AASHTO LRFD. At that time, it had several bugs, particularly, the requirement for substructure reinforcement was much higher than using the standard specs. I worked out an exception to the spec with the client; they were satisfied.

Maybe you need to ask your senior engineers to be more specific about your work. One problem I've seen with younger engineers, they tend to over think and over analyze because with a computer it's possible to consider numerous possibilities. Recently, one fellow in my group prepared an elaborate STAAD model to design a 75' long pedestrian bridge; a waste of time.

Is your company under pricing the work; that's bad? Or are you doing more than necessary?

 

[jimaitken]

Testrun
Check out this thread.

http://www.eng-tips.com/viewthread.cfm?qid=164313&page=1

 

[Ron]

bridgebuster nailed it....follow the standard of care! If you don't your liability goes up tremendously, without regard to what you client "wants".

 

[HgTX]

If the client in question is some government agency, though, they may have put in place their own design policies that override the design manuals. (However, these should be for well-thought-out engineering reasons, not simple convenience.)

Hg

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