Engineering Judgement vs. Codes
Engineering Judgement vs. Codes
(OP)
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.





RE: Engineering Judgement vs. Codes
Having said that, the code often becomes construed as the "minimum standard of care" and to deviate from it puts additional liability on the engineer. We all know that there are times when engineering judgment should supercede certain provisions. My suggestion would be to document both sides of the argument, so that if an issue is raised at some point in the future, then there is a clear path as to the decision process.
Also keep in mind that if the code is not followed and there is a failure, the logical assumption is that if the code HAD BEEN followed a failure would not have occurred. This too, is sometimes a fallacy.
RE: Engineering Judgement vs. Codes
I have heard of cases where cars have been succesfully homologated, even though they did not meet all the written requirements, but not on anything safety or emissions related.
We also have internal standards which are substantially more restrictive than the legal ones, but we can design a car that breaks these standards, so long as we can demonstrate that the sub-standard performance still satisfies the customer's requirements, etc.
Cheers
Greg Locock
RE: Engineering Judgement vs. Codes
RE: Engineering Judgement vs. Codes
A lot of plans inspectors and building officials see things differently than engireers. Their experience and training is more focused on public safety than efficient or seemingly good design.
Everyone knows why doors of nightclubs open outward ( the Coconut Grove fire )but there are lots of other seamingly trivial things that can have an impact on public safety. Lots of people don't know what they are and the rules in place because of them.
RE: Engineering Judgement vs. Codes
Building codes set minimum standards. If you see something in the code that to you feels TOO minimum, just increase your design accordingly. You can then show that you have met the minimum design required by the code, and you even went the extra mile to increase the design due to your judgement.
RE: Engineering Judgement vs. Codes
Code is not god. Codes are created by human beings and human beings sometimes make mistakes. Part of the reason that our engineering education is structured the way it is, is to teach us to think. I meet too many engineers who blindly design to code without knowing the limitations and applicability of code. I suggest examining the code in detail, try to find out why it is the way it is, learn the limits of its applicability, find out the assumptions that are utilized. A good engineer questions everything and assumes nothing.
RE: Engineering Judgement vs. Codes
I think your final sentence is silly.
Cheers
Greg Locock
RE: Engineering Judgement vs. Codes
RE: Engineering Judgement vs. Codes
TTFN
RE: Engineering Judgement vs. Codes
Hg
RE: Engineering Judgement vs. Codes
1. I agree 100% with the fallacies Ron described.
2. Public safety and protection is not an issue, as
everyone agrees that this should dictate the design
above all else.
3. I also agree with JAE in that providing the minimum
(or more) as required by code is the way to go when
possible.
The point I was referring to is a case when a safer structure, in the opinion of the engineer, would result if it were in violation of a particular code requirement. I think that its not a matter of if the code goes far enough, but rather if it goes too far in some cases. I do not have a particular situation in mind, it was just a question discussed among fellow engineers. I hope this makes the topic more clear. Any other thoughts?
RE: Engineering Judgement vs. Codes
Hg
RE: Engineering Judgement vs. Codes
Secondly, if Motorcity (or anyone) has become aware of a situation (via hypothetical reasoning or otherwise) where there is a genuine deficiency in a code that could give rise to a safety issue then surely it then becomes a duty to bring this to the attention of whatever body is responsible for maintaining the code. Codes do evolve to reflect changing developments in materials / methods etc.
Afterall is not the hypothetical situation (if Motorcity had a specific design or structural problem in mind) a form of FMEA ? albeit informal in this case, and are not the codes (generally) the result of formal FMEA and real tragedies, written to prevent failures happening again ?.
RE: Engineering Judgement vs. Codes
RE: Engineering Judgement vs. Codes
I've gotten a number of minor code changes through various bodies by pointing out some discrepancy or other to people in the position to change things. It can be done. If what you have is a weird enough case, though, they would probably say that's not an intended application.
Most contracts, codes, specifications have an option for "the Engineer" to allow exceptions to the code, so your hypothetical situation could be handled under that provision. Just document the hell out of it--if applicable, show calcs both ways demonstrating that what you did is better, and also set down in words the overall logic of your reasoning.
I'm having a major "d'oh!" moment here--most of my job involves handling exceptions to codes, just on a more minor level than I'd thought you were talking about. And very often we'll let something go that's in violation of the spec but still structurally adequate, because the cure may be worse than the disease--for example, a small area reduced in thickness because a defect was ground out often isn't worth introducing a welded repair to the area. Dunno if that answers the original question.
Hg
RE: Engineering Judgement vs. Codes
I supervised over 40 engineers at that time. I advised that we would follow API RP 520 which is a requirement of many of our contracts. I also recommended that the PHD type should present his concerns to API. As far as I am aware no change occured.
Still, the use of engineering judgement is also required. We often speak of codes and standards. As with many standards, the API standard mentioned is a recommended practice. It is common for standards to include verbage that permits exceptions. Document deviation well, distribute to those in authority and proceed with approval.
John
RE: Engineering Judgement vs. Codes
Was the API method more or less safe than that established by your "Chemical engineer doctor"?
Regards
James
RE: Engineering Judgement vs. Codes
Interesting post. Getting away from the structural aspects of building codes, I can give you a good example of deviation of code and applying for a variance. The handling of fuels, specifically the dispensing of gasoline, is strictly forbidden indoors. However, we at a car assembly plant dispense gasoline as the cars near the end of the assembly line to enable driving off and facilitate vehicle testing. Our case for dispensing gasoline indoors is logical and by showing that our equipment, methods and safety precautions exceed the code for the handling of fuels, we had no problem obtaining a variance. This of course is not a unique situation, as every vehicle assembly plant in the world does the same thing. I think the point is that had we not applied for a variance, regardless of our equipment, methods and safety precautions, we would have been in violation of code. Maybe the scenarios are not parallel but as codes are written by engineers and variances granted by engineers when the design and safety criteria exceeds minimums, the inspector's black and white interpretation of deviation/violation of the code means nothing.
RE: Engineering Judgement vs. Codes
"The point I was referring to is a case when a safer structure, .., would result.."
Can't have it both ways. Either safety is an issue or it isn't. If it is an issue, it must come before code requirements.
RE: Engineering Judgement vs. Codes
A compliant design is assumed to be "safe" and is therefore indeed not a safety issue.
TTFN
RE: Engineering Judgement vs. Codes
"...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.
RE: Engineering Judgement vs. Codes
The chemical engineer claimed that the error in the API standard was unsafe - his method safer.
John
RE: Engineering Judgement vs. Codes
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.
RE: Engineering Judgement vs. Codes
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
RE: Engineering Judgement vs. Codes
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.
RE: Engineering Judgement vs. Codes
BobPE
RE: Engineering Judgement vs. Codes
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...
RE: Engineering Judgement vs. Codes
RE: Engineering Judgement vs. Codes
If you are the engineer, change the code and stand behind your decision for all to see....it is that simple...
BobPE
RE: Engineering Judgement vs. Codes
RE: Engineering Judgement vs. Codes
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.
RE: Engineering Judgement vs. Codes
RE: Engineering Judgement vs. Codes
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.