Engineering Judgement vs. Codes 2

[MotorCity]

Here is a hypothetical situation which has generated much discussion among a few of my colleagues. When, if ever, should engineering judgement take precedence over legally adopted design codes or standards (i.e. building codes)? For example, if during the design process you encounter a situation where following a code would be detrimental to public safety or result in an uneconomical design are you still required to adhere to that portion of a particular code? As an engineer, could I over rule a building inspector's decision, who probably has no formal or technical education in engineering? If I am under a contract with the owner to provide design services, am I still obligated to follow the code and seal the drawings if I believe that the design is flawed due to following the code? I know that in most codes there is are statements that say something like "in lieu of a more detailed analysis based on engineering principles......." which provides a loophole, but this is not always the case.

 

[IRstuff]

The poster posited a structure that is "safer" than than a compliant design.

A compliant design is assumed to be "safe" and is therefore indeed not a safety issue.

TTFN

 

[stevenal]

I would propose that an engineer's obligation to public safety doesn't end with a code making committee's today's definition of "safe." "Safer" is always a desirable goal. Codes by nature lag technology, and engineers can affect changes.

"...if during the design process you encounter a situation where following a code would be detrimental to public safety..."

Sounds like safety is very much an issue. Can't have it both ways.


To take this beyond the hypothetical:

A clause in the 1997 and earlier versions of the National Electrical Safety Code was being interpreted in a way I considered to be detrimental to the safety of construction workers in an electrical substation. I let the committee know in a letter, and proposed an exception. The committee took my exception and added to it. See exception 3 of rule 110B in the '02 NESC, and IR507.

 

[jsummerfield]

JamesCG,
The chemical engineer claimed that the error in the API standard was unsafe - his method safer.

John

 

[rhodie]

The issue is:

Do you follow the letter of the law, or the intent of the law?

In my mind, the intent of the law is paramount.*

Justifying such a departure from code -to establish the true intent of the law- would at a later time be easier to explain than, in this context, justifying blind legalism.


* If the law (code) is properly written, the intent becomes the letter.

 

[Slowzuki]

Specific to the Canadian National Building Code, there is something called an equivalence which can be demonstrated by an engineer. A large chunk of our companies activities and from developing equivalences.

There are many mistakes/holes in the NBC and NFC in Canada, engineers don't generally exploit them but others using the code sometimes do.

Even worse are mistakes in some of the local authorities regulations. They do not grant equivalencies.

A specific example is in Nova Scotia, the NS Building Code Regulations that append the NBC require limits placed on building occupany not based on the exiting provided but by using the design factors for minimum exit standards. No credit is given for providing additional exiting from room.

This is a serious limitation making it near impossible to allow graduation ceremonies in gymnasiums etc even if sufficent exits are designed and provided. The authority looks at the table showing the minimum design loads for exits and makes that the maximum number of people permitted.

The funny thing is the table they reference has an appendix entry explicitly saying the table is not intented to limit occupant loads and that it has been mistakenly used to do that by authorities.

Ken

 

[BigH]

Follow the codes to the letter - then sit back and let our wives and building inspectors design. For if the code designs, what is our purpose?
I have seen several times where codes are being followed and the resulting design is garbage - why? The code didn't identify some peculiar point that the actual site condition had - like adjacent footings. Or, the code requires, say 40kg stone for slope protection when engineering tells us that 1kg stones is sufficient. In other words the codes were inappropriate, yet they were codes so . . .
I took up geotechnical engineering years ago because they didn't have many if any codes at the time. I would be surprised if any of the great advances in geotechnical engineering by the pioneers would have been possible if they were constrained by codes.

 

[BobPE]

I like how EddyC put it his/her post, only with a subtle change...Codes were created by engineers for use by laypeople....We make the codes and we can design around them if good engineering practice dictates. We then take responsibility for the design....After all this is what it means to be an engineer...

BobPE

 

[TrevorP]

Interesting thread.
motorcity asks 'if...you encounter a situation where following a code would be detrimental to public safety...'.
This is a hypothetical situation, and I can't think that there could be many cases where this would apply. Usually codes specify a minimum standard of safety. Exceeding this minimum is rarely a problem. If the code were to actually prohibit something that could improve safety, then it would be necessary to understand the reason for this. It might be possible to get round it, but only by following some very definitive steps.
If the code tells me I have to use a 40kg stone, then I think I would tend to use 40kg stone rather than a 1kg stone, even if that was all that was really required. I would, of course, make sure I fully understood the code first to make sure that there were no get-out clauses. But I think it would be cheaper and easier to do that than try to convince my insurance company that the code is excessive, or worse still persuade a judge and jury that 1 kg is adequate for the worst reasonable design case and that it wasn't reasonable to design for the 500 year storm that just hit. If using a 40 kg stone compromised safety on the other hand...

 

[BigH]

TrevorP - the 40kg stone is a safety hazard to the poor 50kg worker who gets the hernia carting it about! I understand your point but there are some codes that rely on "the bigger the better", "the more the better". To compact an expansive clay to 95% modified Proctor is asking for problems once the moisture content increases and causes excessive swelling - still, the spec says to do it.

 

[BobPE]

BigH:

If you are the engineer, change the code and stand behind your decision for all to see....it is that simple...

BobPE

 

[BigH]

BobPE - I'm happy to do it - but sadly, I don't have the final say as I am not the "Engineer" (as per FIDIC or contract) and so so many worry about the "auditors." I fight my battles when I see I have a chance to win. Thanks for the back-up!

 

[stevenal]

"I can't think that there could be many cases where this would apply"

Think harder. The code writing bodies are made of reasonable people, but they cannot possibly imagine all of the interpretations the AHJs will put them to. A little feedback, and they'll close off a misinterpretation or two in the revision cycle.

My October 4 example involved the temporary storage of an electrical vault in a substation yard. The first suggestion by the AHJ was to move the vault outside the substation fence. We patiently explained that the vault was slowly filling with rainwater, and that making it easier for kids to drown would certainly not enhance public safety. Their second suggestion would put workers at risk.

 

[davidbeach]

An example of code not accommodating reality: A building being built on, or retrofitted with, base isolators, total motion being up to 18" horizontally from rest position. Code requires that flexible conduit in service entrances be limited to six feet. That range of motion can not be accommodated in only six feet of 4" flex conduit. The risks of an energized service entrance feed being ripped asunder during a seismic event are far greater than those associated with using more than the code permitted amount of flex conduit.

 

[TrevorP]

Aha, a few good exceptions to prove the rule...(and aren't these always the most interesting?).
Please note the phrase - "I can't think there would be many..." rather than "I can't think there could be any...".
Anyhow, I can't think of anything more valuable than getting the code changed where necessary - so a star for stevenal for that!
Actually, by doing this, you followed what I was meaning by 'definitive steps' - to the end point.
My point was really that, if it is merely an inconvenience to follow a code, then you do so at your own peril. Legislation is becoming more and more onerous all the time, and public expectations of safety higher and higher.