Is manual calculation still needed nowadays in structural design? 5

[ccpe]

I have been working in construction and engineering field for many years. But I have not done any structural design or analysis extensively for at least 10 years although I would analyze structures very roughly or on concept level occasionally. When I was doing structural design many years ago, my manager didn't want to buy computers and software to complete designs. So I had to do everything manually. Fortunately, the company had a small library contained various standards, codes, engineering manuals, etc. I could always found the design data of various loads (wind load, live load for various structures, etc.), property for common material (weight, strength, elongation rate, proportion, etc.) and common structural calculation formulas. But I know that software are so powerful now. They can do almost all structural calculation for us and are much faster. Do we still need to master manual structural calculation skills?

 

[JoshPlumSE]

Yes, manual calculations are essential, IMO. However, it depends on what your definition of "manual calculation skills" is. For me, a "manual" calculation often involves entering formulas into MathCAD or Excel.

 

[WARose]

Do we still need to master manual structural calculation skills?

Absolutely. And just plugging and chugging on some spreadsheet/FEA software without thinking about the underlying assumptions is dangerous.

I personally do calculations (all the time) that there is no spreadsheet (that I am aware of) that can do it.

 

[Ron247]

Ditto, you will always need to be able to do your own calculations. First, I caution you, computer programs have flaws in them. They find out about the flaws by people doing their own calcs and comparing the results. I can easily give examples if I had to.

I also think you are referring to classical structural analysis (slope-deflection, 3 moment etc) as much as you are "calculator skills". You must have a good working knowledge of these to have an idea when your computer output is wrong. The programs are powerful and fast but they are also not responsible for your building falling down.

 

[kingnero]

Whenever I have to do something more than once, I make a spreadsheet for it.
First time use, it gets thoroughly double checked against manual calculations (even when the input is also based on manually inputting formulas/standard values/...).

 

[JStructsteel]

Most of my 'hand' calcs are based on a spreadsheet. That way I can change any variables I want to play around with the design. No reason to do a calc by pencil and paper anymore.

 

[ccpe]

Thank you all for your valuable replies. When I say manual calc., it doesn't mean you use pencils, pens and paper. It means the classical methods, contrary to just enter the data into the computer, let the software do the all calculation and analysis. For classical calculations, you need to find data from authorized resources, such as reliable manuals, codes, standards, data publications, etc. Then choose the proper formula, then apply the results with the reliable resources to choose the size of steel bars, thickness of bearing walls, concrete, etc. The flaw for classical style is that different professionals may come to different conclusions. For example, some professionals may choose 1m x 1m column, the others may choose 0.8m x 0.8m column.

 

[hokie66]

That's not a flaw, it is a benefit. Why should we all be the same? It is called design for good reasons.

 

[skeletron]

Rational manual design often is often very satisfying.

 

[IRstuff]

"The flaw for classical style "

The same is true of computerized analysis, since there is no "right" and "only" answer.

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[msquared48]

Slide rules are needed when the power goes out, so, yes, very yes to manual calculations.

Mike McCann, PE, SE (WA)

 

[oldestguy]

On this subject a question. Can anyone point to a case or cases where computer calculations have resulted in some degree of damage claim against the engineer, faulting this use? Perhaps commenting on the lack of parallel manual checking calcs.

 

[TehMightyEngineer]

I recently found a couple of quirks in my RISA model via rough hand calcs. Rather than fight with the program I reverted to hand calculating the various items I questioned. Wouldn't have caught the issue without hand calcs and hand calcs were the most efficient way to correct the issue.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[drawoh]

oldestguy,

I have been told that everyone today wants to see a diagram with pretty colours, such as is generated by FEA software. When I have done crash safety calculations, I have determined that my points of failure are bolts. Bolted connections are easily but incorrectly modeled by FEA. You really need to do your statics and your moments about a point of rotation.

I did a crash safety analysis on a system that sat on six anti-vibration mounts, three to a side. If each mount were rated at one sixth of the mass of the system, the crash moment would be resisted entirely by the two mounts at the far end. Statically, this is not good at all. Energetically, it probably will work[ ](???). When I am in control of designs like this, there are four (only) correctly sized mounts.

--
JHG

 

[chicopee]

When a contractor that I worked for, slid girders over the electrified tracks in Bridgeport, CT, back in the late 1990's, a hired structural engineer from Brewster, NY did all the calculations, several pages long,by hand. His work took a few months to complete and the project was done at night without a glitch.

 

[msquared48]

See... The electricity went out and he had to do the calculations by hand.

I stand vindicated.

Mike McCann, PE, SE (WA)

 

[ccpe]

'That's not a flaw, it is a benefit. Why should we all be the same? It is called design for good reasons.'
Kind of agreeing with you, hokie66, otherwise there might be no Leaning Tower of Pisa.

 

[XR250]

I still do a lot of things by hand simply because it's faster - time is money!
Most wood and steel beams, joists, wind loads, seismic and sheer walls I typically do on my calculator.

 

[helfreco]

I transitioned from a large company to a small one. I previously had all the software I wanted all the way up to ANSYS (and I used it a lot). My new firm cannot afford software like that. I have an old version of STAAD to do my structural analysis, but I still have to do all my code checks by hand. I have been developing a lot of Excel spreadsheets since I have been at my new job.

Hand calcs are also good for spot checking things real quick.

 

[Sawbux]

I have a solar powered calculator. Will work during daytime with the lights out.