Calculations, Calculation and More Calculations!! 7

[strucguy]

Why is it that I feel, we as engineers sometimes get a little too overboard in doing or asking for calculations for each and every simple aspect of design. I am an licensed engineer myself. And, I am in no way undermining the importance of design calculations in ensuring we deliver a safe and sound structure to our clients. But, when calculations in whatever form they are, overtake our engineering commonsense and judgement, I think it's time to step aside and take a serious look at ourselves and the not so sensible approaches we sometimes take. There has to be a limit to the level of documentation that has to be maintained for any specific design job, so that our efforts can be channeled towards aspects that have a bigger impact on the project. Also, unless we start thinking in terms of systems and not worry about every nut and bolt, we are definitely headed towards a road to nowhere. What are your thoughts on this?

 

[imcjoek]

Also, unless we start thinking in terms of systems and not worry about every nut and bolt, we are definitely headed towards a road to nowhere.

Engineering IS the details.
Take a look at the Hyatt Regency for a good example of what can happen when every nut and bolt is passed on for the next guy to deal with.

On the subject of calculations:
Intuition is very often wrong. Even the intuition of the experienced can fail. The experience is required to understand what the calculations are saying. It is not a free pass to skip them.

 

[msquared48]

Structguy:

Tell your argument to a lawyer and see how far you get. He will love your philosophy, but for the wrong reasons.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[SLTA]

or look at that high rise that Bill LeMessurier designed, one thing got changed, and the whole building could have crashed down. yes, big picture is important, but honestly, connections are more so.

 

[strucguy]

imcjoek...see my original post. It was never my intention to undermine the importance of engineering calculations in accomplishing our everyday design tasks. But, as with everything...there has to be a limit to these calculations too. I have performed peer reviews on projects done by others, and it has always been my approach to understand the intent of the designer rather than checking the whole design. Also, I would never expect to see calc for each and every element on the job. Even if they had all the calcs...I could still find areas where the engineers should have performed some calcs. I don't think a typical engieers budget would allow for an unending trail of calc work. And, I don't think my budget would allow me to check each and every element of the structure as part of the peer review.

My original post was in regards to many trivial redesign issues that we come accross during the course of a project. Say...the client wants to make a 1 ft square hole in 30 ft wide masonry wall, drill a 6" hole through the slab at the middle of 30ft x 30 ft bay. If you can't take an engineer's word for issues like these...and expect to see a piece of paper with fancy stress strain analysis, I am forced to think that either my license has no value or the reviewer has some issues with his intellect. Mistakes do happen in the kind of profession we are in...but that should by no means cipple us from using our intuition that we as engineers have gained from years of experience.

 

[hokie66]

strucguy,
Maybe these other folks don't understand what you are saying, but I do. Engineering still must involve judgment, not just slavery to indecipherable code provisions. Having a detailed calculation for every conceivable thing in a structure does not insure safe designs unless accompanied by a good dose of common sense, which unfortunately is too uncommon these days.

 

[LiteYear]

This topic comes up every now and then in Safety Engineering discussions - there are proponents of the theory that a well specified and calculated design creates a safe product and there are critics that say that this approach can blind the engineers to applying judgement. I tend to ensure that at least the latter argument gets heard. The former argument reminds me of well meaning, but ultimately flawed "proofs" people have tried to use to convince me of something that is blatantly false.

The issue I think is that there tends to be an air of unwarranted awe in formulas. But a formula is subject to the same principle as a computer - GIGO. Even applying the formula again, and again and again doesn't fix issues of misapplication or misinterpretation. I'm a particular fan of applying judgement that represents an alternative approach to the standard applicable calculation. Too many times I've seen someone establish an hypothesis (that forms a prejudice) and then construct a calculation that simply confirms that based on their invalid assumptions their conclusion is correct.

This of course, is a common criticism in Safety Engineering - that so much time and effort is spent on working through mechanistic calculations, that the task of stepping back, considering and applying sound engineering judgement is overlooked.

 

[cranky108]

This sort of goes along with consultants asking for to much data or providing to little.

A few times a year I get sent a page questionare, front and back, asking for specific data. I know they don't need it all, and the engineer that sent it is looking to take one number and put it into a formula somewhere. But he sent me the whole questionare.
The worst thing is on a big project, I will see the same questionare from different engineers at the same company. And my answer to them, when I call them, is always "it depends on what you need it for". If an consultant can't tell me why he needs a piece of data, then he dosen't get an answer.
And they never seem to understand what difference it makes. It's simple, it changes my assumptions.

Bottom line, don't send me a one page questionare if you only need one answer. Don't waste my time.

So I do understand about over the top calculations, because other people don't want to communicate.

Put an end to useless, and unused data.

 

[Twoballcane]

“Say...the client wants to make a 1 ft square hole in 30 ft wide masonry wall, drill a 6" hole through the slab at the middle of 30ft x 30 ft bay.”

If you get requests like this and you are not asking the right questions in return, small request like these are the ones that bite you in the a$$ at the end. The only way to be diligent in your designs especially if there are loads and moments is to go thru the analysis. I think of it as a check list to make sure it is ok because you never know it may turn up something the requester did not realize or did not tell you. You may get down to loads and the requester will come back and say “oh, so we can add a 10 ton thing a ma jig thru it…will this break something?”. So the hole may be innocent, but the application may be over the top.


Tobalcane
"If you avoid failure, you also avoid success."
“Luck is where preparation meets opportunity”

 

[JAE]

We had a big discussion some time ago about calculations - specifically their purpose, use, and mis-use.

Here is the thread: thread507-89434

 

[DHambley]

"What are your thoughts on this?" My specialty is electronics, quite different than structural but this "calculations issues" are the same. It takes someone with enough sense or experiance to know what requires detailed calculations and what can have a simple margin applied. As stated above, a bunch of calculations does not ensure reliability. A practical person would know that you don't need 0.1% accuracy when the tolerance study shows you only need 50%.
I got paid a lot (from your tax money) as a contractor several times to "analyze to death" several circuits for spacecraft. The original design was very sloppy; high voltage spikes causing noise on the mixed-signal boards, transistors running very hot, and all sorts of other problems. I wasn't allowed to change the circuit, only to perform analysis showing how reliable it was....but is wasn't reliable. You'd go down to the lab to run a test and half the time something would break. The good news for taxpayers though: it had lots of paperwork with the word "Quality" stamped on every sheet and lots n lots of calculations.

Oh, and the first two comments were from people who thought your question was, "Can you please write a worthless, sarcastic comment?" I re-read your post....um...nope. Didn't see that question in there.

 

[cranky108]

If you don't want a sarcastic comment, then don't ask an engineer.

 

[GregLocock]

I'm struggling to see any sarcasm in imcjoek's reply.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[VoyageofDiscovery]

Be happy the Clients want calculations, these are your only defence in court. Loads change, expectations change. When it's all said and done this is your mark within engineering, it records what you did. When it is given to your Client, they own it to some degree as well as they may have given you some parameters. Computers today make it a cinch. One more thing, calculation without experience is nothing, experience without calculation is nothing, put it together, it's everything!

VoD

 

[beej67]

Engineers need both strict adherence to getting the details right, AND the intuition to know when those calculations don't seem right. You need both. One doesn't cut it.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[imcjoek]

I'm struggling to see any sarcasm in imcjoek's reply.

I'll try harder next time.