who doesn't use manual computations anymore? 5

[pattontom]

More than half of local structural engineers I know doesn't use manual computations anymore. They reason it's long process to get for example the biaxial interaction diagram, moments of each columns and beams and their interactions especially if they are designing very tall stories. So they rely on ETABs for example which is complete package and can even produce complex spectrum seismic analysis that would take 3 weeks for just one projects. As you know ETABs can automatically calculate all the moments and shears of each element and their combinations that you may miss out manually. So who amongst you also use such package and no longer do every process manually? And for those who do manually and spend 3 weeks for just one project writing dozens or hundreds of handwritten paper, what do you think the ETABS folks can miss out when they don't do each member manually?

 

[TLHS]

I don't do all the engineering by hand on anything other than a small or unusual structure. On most structures, though, you'd never go through the process of sizing each member even if you did the whole process by hand. You'd identify the possible worst cases members and only end up sizing a handful of members.

No matter the size of the project, I pretty much always do preliminary sizing entirely by hand and have a pretty good idea what it'll all be before I put it into software, at least for strength governed cases. The engineer generally has a pretty good idea on what the governing case will be and where the worst member(s) will be. Doing those by hand to start means that the structure's mostly designed. You can do simplified or conservative capacity checks on those pretty easily. Then, when the computer does it's check, it acts to confirm what you already knew.

You either do it that way, or you do it in reverse where you do the model and then check by hand. I just find it faster to figure out member spacing and general parameters by hand on a piece of paper rather than having to remodel to optimize things.

Even on complete finite element models I wouldn't be comfortable doing something entirely by computer.

I'm a young engineer, so none of the above is because I'm not comfortable with computers. I just recognize their limitations. Computer models are difficult to check comprehensively. There can also be issues with software where it doesn't act how you think it's going to act because your assumptions are different than those of the software developers.

 

[hokie66]

If an engineer doesn't use BOTH manual and computer aided calculations, he is not doing his job adequately. I would add in the "cookbook" as well, as lots of design aids are available to make life easier.

 

[IDS]

I do my hand calculations on the computer.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[jwilki]

Design aids and programs will take you so far, but they will not help you understand underlying engineering principals. I too perform preliminary design by hand and confirm them with software/aids or I stick my design loads into the ‘blackbox’ and check some critical results it spits out by hand.

 

[IDS]

Design aids and programs will take you so far, but they will not help you understand underlying engineering principals. I too perform preliminary design by hand and confirm them with software/aids or I stick my design loads into the ‘blackbox’ and check some critical results it spits out by hand.

I disagree, I think "hand calculations" vs "computer calculations" is a false dichotomy. It's quite possible to follow a pre-defined "hand calculation" without gaining any understanding of whether it is appropriate, and it's also quite possible to use computer tools to investigate how a structure will behave under different assumptions, and to obtain a better understanding of the problem than would be practicable using purely manual methods. I'd say the question should be: do you use automated design processes, or do you think about it?

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[msquared48]

All my calculatins are done by hand, computer or otherwise.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[hokie66]

It's not the hand that matters, it's the brain.

 

[pattontom]

For those who haven't used ETABS. Try putting just a simple beam supported on a column. Enter the uniform load or point load in the program. You will find out the moments produced by the program is the same as when you calculate it using manual formulas. Now add it it many elements and the manual computations would be taxing. This is why ETABS and STAADs are so popular because they are just formulas put on graphical interface. I wonder how many percentage of you use ETABS and STAADS. What other softwares are like them? It is a known fact that engineers above 50 years old are not familiar with them because these software are not available when hokia66 (who is 66 years old) and BAretired (who is above 60 years old too as he is retired) for example are in their younger years (and only Atari or Apple II computer available).

 

[haynewp]

LOL

 

[hokie66]

Not true...it is not a "known fact". I am more than 66 years old. I have used computers throughout my career, and have written programs. I have used ETABS, but more often have interpreted the output. I don't resist using computers. But the key is to know approximately what the output should look like before you start inputting. Just plugging into a black box and blindly accepting the results won't make you an engineer. It won't even make you a good technician.

 

[paddingtongreen]

I'm 77 and retired, but I've been using computer programs since 1970, mainframes and desktops. I roughed out my member sizes and estimated the load paths so I could speed up the de-bugging if I got a different output.

Please don't make unsubstantiated assertions about we experienced engineers.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[rowingengineer]

The only "known Fact" in this thread is that Pattontom has heard some very poor advice and is probably to young to know it.

The computer is only as good as the user, if the engineer doesn't know how to model the beam correctly than the computer isn't going to do this for you. The computer can help you as long as you tell it how to. Sure you can probably do all your calcs on the computer, but if you think that one program is going to handle all these calcs than that would be foolish. You must have ways to ensure the program is correct.

lets review the problem put forward, a beam supported by a column, will real life match my model? Give we are only suggesting one column and one beam so the beam must be cantilevered evenly each side of the column. As such the column must take moment to the foundation for your patterned live load as a minimum, Did we size the foundation for this moment or just uplift.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[JohnRBaker]

In the case of engineering, computers (and the software on them) can be seen as 'amplifiers' in that they allow experienced and competent engineers to do more work, quicker and more consistently.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[msquared48]

pattontom:

I guess I'm over the hill too at 64, the young one in the bunch here. I've dealt with computers since 1966, and, obviously am more convinced of their programming limitations than you are.

I guess someone needs to hire you while you still know everything. I think you just may have lost a lot of expert mentorship on this forum. Good luck.

Mike McCann
MMC Engineering

http://mmcengineering.tripod.com

 

[pattontom]

I'm asking this because a company which designs 20-50 storey buiilding and above used entirely ETABS outputs in their calculation sheet. They don't put any formulas.

When doing 2-storey. Of course I use formulas in excel. I don't rely entirely on ETABs. But for the 20-39 storey designers. They just use ETABS.

Anyway.I wonder who amongst you design 30 storey too? The period of tall stories are bigger hence they can withstand seismic better... so is it a general case that maybe short 3-storey are more seismically challenging to design than 30 storey? No. I won't try 30 storey. Just asking. Thanks.

 

[Parrapit]

I am also a youngster and out of my experience I have realized that the more senior guys are the limitations to a design program. The reason for this is that they have a set way, of doing a design and using the program all these years and when new features are added they still rather use the "older" method of analysis on the same program which they are comfortable with.

Which is fine in my opinion but there designs are a lot more conservative at times. Example when a 3D method of analysis is added they still prefer to use 2 planes only but the third plane will also help in the stability of the structure.

I guess its fine but I personally like to be as economic as possible. Please don’t get me wrong I respect the more experienced guys as the teach me a lot.

I only use hand calculations for my loading and the programs for the rest but also have a tight relationship with the program designer’s technical team.

 

[rowingengineer]

Pattontom,
If I was supplying calcs to someone, I would only provide computer generated outputs generally, however this wouldn't be a true reflection of all my calcs. Reason for this is that I would only provide the major analysis components, not my checking or non-typical calcs. And yes I do design building over 30 stories, but find that the complexities don't really start until you get over 55 stories.

"The period of tall stories are bigger hence they can withstand seismic better... so is it a general case that maybe short 3-storey are more seismically challenging to design than 30 storey? No" I recommend you read up about soft stories and a few books on medium building complexities in design.

Parrapit,
Please don't lump all senior engineers into the same area. Most of us are update with our programs. I found a fault in a very common program only the other day that the developers admitted that it had been there from day dot. my normal rule of thumb is that a new design feature will take 6 months to be fully tested before you can trust it with any confidence and then I always do a quick check

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[IDS]

Please don’t get me wrong I respect the more experienced guys as the teach me a lot.

I'd hate to see how you talk about people you don't respect then.

FWIW, I'm another one in the right side of 60 club (i.e. born pre-53), have used computers all my working life, and have a methodology similar to that described by rowingengineer.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[IRstuff]

Obviously, I'm not in this industry, but I use tools in accordance with their application. There are calculations where I have created Mathcad worksheets with manual equations; and there are calculations where manual calculations are impractical. No building height limitations here, just tedious and repetitive calculations that would require about 100 times longer to do the calculations manually.

I expect that all engineering disciplines have a similar situation. My ME cohorts would readily agree that almost all their stress calculations for our products must be performed with FEA, based on meshed networks generated from CAD models. Almost nothing that they design are amenable to manual calculations, because the shapes and geometries are too complex and are not readily describable with simple equations. Thermal analysis can be performed piecewise using manual calculations, but the system level calculations can only be done with application specific thermal analysis packages, since the designs invariably would require massive matrix operations.

TTFN
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