Responding to Plan Checker's Comment (the polite method) 33

[SE2607]

I have a plan check comment that one of my beams is 2% overstressed. While I always try not to exceed a CSR ratio of 1.0, it sometimes happens (putting a bigger beam is expensive, not available, etc.). This is a wood-framed residential remodel, which should be as safe as any other structure, I find this ridiculous. I could reduce the assumed dead loads enough to make this work, but I'm wondering if there are any provisions in the code which allow me to do this.

TIA

Sorry for the double post.

 

[ChorasDen]

Purposely providing a design check with any amount of overstress is certainly not wise from a risk management perspective

What would your insurer say to you designing to a ratio that exceeds capacity?

 

[Tomfh]

2% overstress will not fail

I think we all agree that a 2% overstress alone is very unlikely to cause problems, that’s not the issue here.

Think about the "newspaper test". imagine you designed a structure that did not pass a code strength check, which you decided to overlook, and then it collapses for some reason. Picture the possible headlines. Imagine friends and family reading, “Engineer knowingly approved faulty design”. I’ve witnessed people in these predicaments, standing before regulatory boards, desperately arguing that their slight deviations were not the cause of a disaster. It’s a situation you want to avoid at all costs.

This scenario is akin to being just over the legal alcohol limit during a fatal accident. Even if the alcohol didn’t directly cause the accident, being over the limit can heavily sway fault determination against you. Blame is frequently assigned this way, reflecting a common human inclination to find someone accountable. In these cases, who better than the engineer who knew the design didn’t meet the required standards?

Experienced construction lawyers, investigative journalists, and professional boards are very good at articulating these points in a compelling way.

 

[SE2607]

I don't even agree with this statement as an absolute certainty.

I emphatically agree. If those other other things, particularly if the contractor made significant errors.

What would your insurer say to you designing to a ratio that exceeds capacity?

Probably: "We would rather you design such that the CSR does not exceed 0.80.

 

[JLNJ]

Just doctor up a few numbers to "fix" it. Then be on your way.

If push came to shove your lawyer can line up 100 engineers who wouldn't bat an eye at 2% over. Heck, by then it would be an existing building and, per the IBC, you'd get to go over 5% with no penalty.

 

[Brad805]

"What would your insurer say to you designing to a ratio that exceeds capacity?" Not a darn thing. They care about claims. Well, that is how it for me in Canada anyway.

 

[Euler07]

This scenario is akin to being just over the legal alcohol limit during a fatal accident. Even if the alcohol didn’t directly cause the accident, being over the limit can heavily sway fault determination against you. Blame is frequently assigned this way, reflecting a common human inclination to find someone accountable. In these cases, who better than the engineer who knew the design didn’t meet the required standards?

I think this is a good point. If the beam did fail, for reasons not to do with the engineering (for example builder's negligence), then having FAIL written on the report would not do you any good in a court of law where the outcome of the case is decided by the emotions of a single individual on that particular day.

 

[SE2607]

This scenario is akin to being just over the legal alcohol limit during a fatal accident.

This is a great example to prove my point. If the legal limit is 0.08, 2% over that would be 0.0816. I doubt if machines can measure that accurately.

 

[phamENG]

My take on the engineering judgement argument is this: we get to exercise judgement on the inputs. We determine what loads are applied and where. The code tells us minimums in most cases, yes, but unless you're designing a box (or other specific shape laid out neatly in the pages of the code), it's not a cookbook. Then, once we've used our judgement to lay out the design and determine the necessary inputs, we start an analysis. Here, too, we have an opportunity to exercise our judgement. What simplifying assumptions can be safely made? Do we use FEM or an old book of 2d frame formulas? Etc.

Then comes the magic moment: comparing the results of our analysis to the code limits. The only opportunity we have to exercise judgement at this juncture is to determine if we agree with the results or not. Did we err in our judgement when making the inputs? Did we make a mistake in our calculations? These are very valid questions to ask, and the more experience we have the better we are to judge the result. But the result is the result. It is either correct or it is not. If it is correct, then we use it - if the beam is over stressed then it is over stressed. Over stressed does not mean failure. It means that, based on accepted engineering practice, it will not be as reliable as we expect components of our buildings to be under a wide range of unpredictable circumstances. But if we feel that result is not correct, then we go back and fix the mistake we made or reconsider whatever assumptions were made earlier in the process.

If you're opinion is that we can't count on our results being accurate to a DCR of 0.00....why was yours reported as such?

 

[Eng16080]

A few more thoughts, mostly just repeating stuff already mentioned above (before I block this site for the rest of the day!):
[ol 1]
[li]Even if we all agree that a 1.02 code check is unlikely to result in an issue, why invite the potential scrutiny? The general public will perceive it as black and white. You're taking on risk for no good reason. Per the example above, you really want to risk being at 0.0816 when you could have easily been at 0.0799? The two are not the same. While you might be able to argue that 0.0816 is ok because you "doubt if machines can measure that accurately," if nothing else, you now have to prove that![/li]

[li]I'm currently going through the slightly painful process of getting insurance, working on a solid engineering contract, etc. The term that keeps coming up is standard of care, which basically means providing engineering services that are roughly equivalent to competent engineers performing similar work in a similar location. I would be concerned that showing a beam calc. which indicates a 2% overstress might not meet the standard of care. I could be wrong though. It could meet it if others in your area have a similar practice. I would certainly be cautious though. Now, would an insurance company deny a claim for this reason? I would hope not, but I wouldn't put it past some of the slimier ones.[/li]

[li]Finally, I think if this thread had been about you being blamed for a structural failure/problem and it was discovered that some of your calculations indicated a small overstress, I think we would likely all jump to your defense, saying that the problem couldn't have possibly been due to that or due to that alone. I see what you're doing as a risk with no reward, and my intention is only to try to help a fellow engineer out, considering that you don't see it this way, which to me is surprising.[/li]
[/ol]

 

[jerseyshore]

Some great discussions in this post that really reflect the fine line we walk when a calculation can be black & white as pass/fail even though the process and reality of it is much muddier.

But to take the attitude of the plan checker being in the wrong over a failed calc you submitted and then coming on here to crowdsource a code provision to prove your point instead of just fixing your own calc is wild. It's not an "up for interpretation" code section you're looking to get backup on. Half the code officials around here can't even read, but they would sure as hell understand the word FAIL on a calc and make you resubmit.

 

[JLNJ]

LRFD vs ASD can vary by far more than 2%. LRFD is usually more efficient for light-ish live loads.

Calc it up in LRFD and blow the plan examiner's mind with FAILS ASD but (easily) PASSES LRFD.

 

[StrEng007]

After the amount of time dedicated to this topic, we all could have answered a couple RFIs and revised some calculations.

Regardless of over/under... at a certain point the business side of your practice (something most of us have to learn by ourselves) should take over and you'll do what is required to get this project off your list (what is legal or towards good practice). If that requires you to make some revisions to satisfy the "more conservative" view of the building official, you should be thankful they have brought this to your attention. If you got enough time to bury your feet in the mud and resist, you must not have a lot of work.

Sometimes you have to put your ego aside because you never know if you'll cross paths with this reviewer again, or what shortcuts the other players are willing to take. IMO, it doesn't matter if you're the smartest person in the room... the work that we do is not a competition to see how well you can toe the line of the Code.

 

[XR250]

I'm currently going through the slightly painful process of getting insurance, working on a solid engineering contract, etc. The term that keeps coming up is standard of care, which basically means providing engineering services that are roughly equivalent to competent engineers performing similar work in a similar location. I would be concerned that showing a beam calc. which indicates a 2% overstress might not meet the standard of care. I could be wrong though. It could meet it if others in your area have a similar practice. I would certainly be cautious though. Now, would an insurance company deny a claim for this reason? I would hope not, but I wouldn't put it past some of the slimier ones.

You might be surprised how low the bar is for standard of care in your area. Honestly, based on the questions you've asked and answered in the past and the fact that you simply show up on the site likely means you're going to be way above your local standard of care. We have a particular local firm that makes it easy for the rest of us.

 

[Eng16080]

You might be surprised how low the bar is for standard of care in your area.

No, probably not. I've seen plans by others. Some are good, but most aren't. I suppose from a legal/lawsuit perspective it's a good thing for most of us here if the standard of care is low. On the other hand, though, it can be hard to compete against other firms who are keeping the bar low.

I'm sure most people on this site who are voluntarily using some of their free time to think about and discuss engineering problems are way above the standard of care (even OP with their 2% failed beam).

 

[EZBuilding]

The standard of care thing is kind of a red herring, as in litigation you won't actually be judged against the actual standard of care in your area but rather the standard of care crafted by the litigators on the case. The profession as a whole should do a much better job of controlling and defining the standard of core to protect it's professionals, but leaves it to the lawyers instead.