who doesn't use manual computations anymore?
who doesn't use manual computations anymore?
(OP)
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?






RE: who doesn't use manual computations anymore?
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.
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
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/
RE: who doesn't use manual computations anymore?
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
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).
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
Please don't make unsubstantiated assertions about we experienced engineers.
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: who doesn't use manual computations anymore?
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."
RE: who doesn't use manual computations anymore?
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.
RE: who doesn't use manual computations anymore?
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
RE: who doesn't use manual computations anymore?
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.
RE: who doesn't use manual computations anymore?
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.
RE: who doesn't use manual computations anymore?
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."
RE: who doesn't use manual computations anymore?
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/
RE: who doesn't use manual computations anymore?
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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RE: who doesn't use manual computations anymore?
I am not a structural engineer and I never designed a static structure bigger than a garage and then I had a structural guy check my beams and footings, however a computer is a computer and a calc is a calc and some rules are universal.
I have successfully designed a few structures that have wheels and are towed along roads at some speed, all by hand and rule of thumb and dead reckoning. None ever catastrophically failed and all where substantially lighter than commercially available products. I had them built and running before a computer only jock would have finished the drawings.
I have also used computers since they occupied several floors of a large office block which was obviously some time ago.
I have also been around long enough to appreciate that electronic devices can and do make mistakes. I mean give me a break, just how many silicon layers at a nano thick are in a computer chip and how many chips and possible routes are there for an electron to travel around all the boards and through all the chips. It's actually incredible that they don't all get lost or diverted to the wrong spot or the right spot at the wrong time.
When was it that Intel had the floating point problem.
I know I personally had a simple pocket calculator way back when that repeatedly gave a very obviously incorrect result to a particular simple calculation. Lucky is was wrong enough so that a simple thought process identified the error. It was the type of thing like say working out the area of a circle say 3.something inch dia and the answer came out to thousands of sq inches.
I repeated it at least 5 times and gave it to several colleagues to check. We all got the same patently wrong answer from the same input. A simple change of one character in the input gave correct results, but going back to the original calculation even after other correct but different calcs still produced the same error.
As a result, I always check my calcs by several methods including a rough in the head to test for ballpark accuracy. Anyone who does not is well on the way to landing face first in the mud. One of your mentors actually needs to give you a little trip and a firm push so you learn the hard way as that seems the only way you will learn.
Regards
Pat
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RE: who doesn't use manual computations anymore?
"People will work for you with blood and sweat and tears if they work for what they believe in......" - Simon Sinek
RE: who doesn't use manual computations anymore?
I think you will find that these programs are not just a collection of formulae. How many would they need to cover every single eventuality?
Pretty much all analysis programs give wrong results. They lie to you. You just have to determine if the results are close enough for your purpose. That is where your judgement comes in.
RE: who doesn't use manual computations anymore?
I have done way too many hand calculations in my day. But that experience usually gives me some insight as to what my first trial sizes should be. We don't to 30 story structures, but we do model large industrial facilities with 2 to 3 floors and lots of differing equipment loads.
I too have been using computers since 1970 - of course they were main frames with punch cards. My first matrix analysis and finite element classes were in 1973. My biggest pet peeve is people that refer to matrix frame analysis programs as Finite Element Analysis. Two different animals.
My next pet peeve is trying to model everything: girts, purlins, stair stringers, etc. That is absolutely nuts.
So I try to be computer literate, but I still design with ASD and the 8th Edition AISC manual on my desk. It sits on top of the 13th Edition which gets opened far fewer times. But since the programs design the members per the Codes I specify, it is not necessary to dig too deeply in the manuals any longer.
gjc
RE: who doesn't use manual computations anymore?
I guess you can consider me a "youngster." I'm in my early thirties, but I'm no spring chicken, either. I echo the sentements of many of the engineers that have commented, including the engineers who are over 50.
I use computer analysis software almost on a daily basis. But, I always back up the results it spits at me with some form of hand calc. Why? Because very smart and experienced engineers taught me not to trust them.
When you are working with a large structure (or any structure for that matter), how do you know your analysis is correct? How do you know if you have proper load paths? How do you know if your structure's dynamics is in the ballpark? How do you know if your software is giving you a "correct" deflection for a beam? Do you even know what your software is doing or how its doing it? I'm not saying that you need to do everything twice. What I am saying is a responsible engineer would verify his/her work to ensure that what the computer spits out is accurate, even if it's just a bunch of scribbles on a piece of scrap paper.
There is nothing wrong with soley including computer inputs and outputs in your calculation package. I do that all the time. I make sure that I am 10,000% comfortable with what I am putting in.
Just a tip, the engineers who are over 50 (as you describe them) can offer you insights to engineering in ways that no code book or textbook can. Instead of insulting someone because they are "old," I suggest you show a little respect and listen to what they have to say.
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
Not really important, but I'm just curious why that peeves you. The way I see it, a beam in a frame analysis is just a particular type of finite element, so it is finite element analysis, just as much as models with plate or brick elements, or any combination of the three.
Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
I am an "older engineer". As Mike McCann noted, he has been using computers since about 1966...I'm not far behind him. Early 70's for me.
In high school, I taught my math class to use a slide rule....went through engineering school with one until my senior year. Amazing how many times over the years I've calculated things in my head that were within a few percent of the answer obtained by more accurate means. Sorry you younger ones have missed out on such thought provoking processes. Did it just today with my younger protege.
I'm also no stranger to sophisticated computer analysis....but my prior "training" has taught me to be suspicious of the output and to look at it critically. Computers are tools of the profession....they don't provide the engineering judgment...just the mathmatical manipulation. If you depend on them to solve engineering problems, you are using them incorrectly. If you depend on them for expedience in the mathmatical process...then you have the right idea.
Though an expensive camera can show a scene in its proper context, it takes a photographer to compose a photo that captures the nuances of the scene. A piano can render all the notes of a musical scale, but it takes a composer to assemble those notes into a palatable melody. The engineer must compose on the computer.....his instrument, his tool, his canvas.
RE: who doesn't use manual computations anymore?
Hand calcs and other design aids, such as books and tables, allow rough design to be done as a sanity check. Randomly verifying things like single beam moment and shear values using quick hand computations help identify where problems might be. Simple tributary area and loading computations, combined with span information make sure that loads were applied properly. If things don't add up, you need to find out why. Blind reliance on the blackbox is not a good idea, but neither is doing every calc twice by hand, to verify the verification. In safety or reliability analysis, the human is the weak link vs a machine, so don't make the mistake of blindly accepting hand calcs, either.
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
Regarding slide rules, my mentor told me that whe he was starting out his mentor had a slide rule with a broken cursor - apparently it was only able to read to two digits worth of accuracy. He didn't replace it because, as he explained, that's all you need. My mentor told me that that left quite an impression on him. It's a shame those dudes didn't realise they need 14 digits worth of "accuracy".
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
For structural members, the stiffness matrix is comprised of the terms that relate the internal forces in the member with joint displacements - such as PA/L, 12EI/L^3, 4EI/L, etc. Then the structure is solved like a complex spring where [P] = [K][d]. Joint displacements are solved for first and then member internal forces are found using the assembled stiffness matrix and the applied loads.
For finite element analysis my interpretation is; the relative displacements of the nodes on a particular element are defined with respect to one another (i.e. it's internal element stiffness); an overall stiffness matrix is developed, the displacements of nodes are solved for; and then the internal stresses of the elements are solved for using the internal stiffness fomulations that were used to define the element.
Here is a much better answer from thread earlier this year (thread507-323635: Finite element analysis)
Hello, Can someone please explain to me, without getting overly technical, what exactly a finite element analysis is?
Thanks.
. . .
JAE (Structural)
10 Jun 12 12:33
Powers - very tough to do that well without knowing what you do know.
Are you are familiar with frame analysis programs where you have beams and columns represented by "stick" members - a member that has a joint at either end? You connect all these into a frame or other representation of a structure and by knowing the deflection-force relationship between the two joints you can analyze the structure.
These two-joint "sticks" are two-joint finite elements. They are essentially a member/entity that creates a relationship between two joints. If you move one joint, the other responds with a defined force.
Each joint, typically - in 3D models - represents six degrees of freedom - X, Y, and Z direction translation and X, Y and Z direction rotations.
Now if you expand that two-joint member into a three or more joint member, the member now becomes either a planar flat element (triangle or rectangle) or perhaps even a solid element with multiple joints that all are related to each other in terms of displacement and force.
The analysis/solution is similar to the two-joint member except there is a problem. The two-joint beam type members can be analyzed such that both equilibrium and deformation compatibility are satisfied (Sum of forces/moments = 0 and the deflection of element A at a common joint with element B is the same). However, with more than two joints, you can't satisfy both of these - only one. Most all finite element solutions choose to satisfy the deformation compatibility and then by keeping the size of the elements small, minimize the sum of forces error in the model.
And then the mesh can be refined to determine if you are honing in on the approximate answer.
gjc
RE: who doesn't use manual computations anymore?
I haven't stopped checking calculating machines' output since I discovered that some of the TI-55's user registers were also used by the machine for intermediate results of some of its built-in functions.
In the meantime, I've learned to program microprocessors right down on the silicon, and gotten pretty good at it, I think.
I still don't trust the damn things.
Mike Halloran
Pembroke Pines, FL, USA
RE: who doesn't use manual computations anymore?
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: who doesn't use manual computations anymore?
If welding is impractical at all, even in places with smaller forces, can slip-critical bolts be used in order to avoid the reduction of capacity due to bolt holes?
RE: who doesn't use manual computations anymore?
Wrong thread I think.
Regards
Pat
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RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
Anyone that relies solely on hand calcs at this point will get left in the dust in terms of schedules and budgets.
Anyone that relies solely on what the computer says is not doing engineering, they are doing data entry.
RE: who doesn't use manual computations anymore?
1. difficult to hang on one's belt...kept interfering with normal gait...
2. immediately placed more pressure on the engineer...everyone expected a more accurate design up to three decimal places in some cases..
3. had a tendency to bind-up under times of extreme pressure/tension like when you found out you were 4 weeks behind schedule with 2 weeks left to deadline...probably as a result of that death-grip...
4. had same design/member sizes as the 12" slide rule and in my opinion was under-designed..they probably used LRFD in the design to whack the last 0.2oz out of it and as a result had the common deflection problems...
5. not easy to carry...as a result, one would tend to carry it either as a cutting-edge engineering tool or as a stick...in fact, both came in handy at times depending on the make-up of your design office...
6. had no well-defined sweet spot so, as a result, one could loose 0.1 seconds in a normal engineering calculation which over the life of the engineer could really add up..
I could go on but I think you get the picture..
RE: who doesn't use manual computations anymore?
* As football helments became stronger players started using their heads as battering rams thereby causing neck injuries.
* As tennis rackets became larger professional games turned into little more than serving contests and viewership declined.
I'm sure there were many non-sports examples as well. But in our industry, as computation machines improved there came with it some unintended and undesirable consequences. The main one, in my opinion, is that the building and material code writers seem compelled to keep up with them. Honestly, what firm could comply with the various codes without "black box" software to grind through all the requirements...and still stay in business? You don't even have to get past Ch. 2 of ASCE-2 to see that. Finding the worst load combination for each member by hand would take 1.2 Days + 1.6 Weeks + .5(Lightyears or Something Rediculous)...so off to the black box we go. (And remember, the affects of one or more of those factors not acting must also be considered and it's easy to get lost in all the numbers. And that's just to get started.)
Then there becomes the problem of people not having much clue how the output they are using was generated...
Seasoned engineers who saw this all slowly evolve on their watch don't usually have too much of a problem with it...one change at a time isn't hard to take and they can make their own real world sanity check without the computer. For the new engineers, on the other hand, it's a much different situation and their dependence on black box computer software is much greater. The situation does the whole profession a disservice, in my opinion.
All of which brings me back to the topic at hand. That is, it wouldn't hurt my feelings if the licensing exam required the use of slide rules and disallowed even simple electronic calculators. Maybe then there would be some push back to the Rube Goldberg philosophy of code writing.
RE: who doesn't use manual computations anymore?
Confirming things by hand, or doing preliminary sizing by hand (where 'by hand' could include spreadsheets or things like mathCAD) doesn't take a lot of time.
It's not a question of not trusting computer programs. It's a question of not fully trusting anything. Fear is an engineer's friend. It shouldn't keep you from taking action, but it should be there in the back of your head reminding you of the consequences of what you're doing. You have to understand the action of your structure and be able to take responsibility for the actual math that went into it. With experience you can get the understanding of the structure from a computer model. That's great, it speeds things up and can let you do things that aren't reasonable by hand. There are two places where there are issues though. In the first case, you could have a situation where you become complacent and treat it as a black box without actually understanding the structure. This is dangerous. In the second case, there could be an error in the way the actual math, model or assumptions are implemented.
You have to be able to look at the structure and the results and be completely sure you understand why the reactions and stresses are what they are in each component. If you ever hit a situation where you look at something like the force distribution in a structure and don't immediately understand why it looks like it does and your response isn't to sit down and figure out why it looks like that, you're not actually engineering anything. If someone asks you why some critical load or reaction is what it is, and your answer is that the computer reported it, you've done something wrong. That's the first situation above.
In the second case, it's a question of verifying because it's not a perfect world and people screw up. It can be anything, but you have to be more careful with things like computer software because you didn't actually write it. If you don't check it, you're implicitly taking responsibility for the work of the software company. If your structure breaks because of an error in the software, they're still going to blame the engineer.
It's not like anyone goes and does a computer model and then checks it with a check of all the load cases and using all the special case code formulas on a piece of paper. You're going to use tables and simplified assumptions and formulas that you've simplified from the code or from other sources. I, personally, like to put pen to paper as much as I can, but it's personal preference more than anything. Nobody's going through the world checking things by doing hand checks for the code check on a beam-column using the full steel interaction formula on a piece of paper for every item in the structure. First off, people are really only doing math for items that could reasonably be critical. Secondly, they're either using a spreadsheet that they've verified or they're using a simplified formula (My/Myr+Mx/Mxr+C/Cr at the simple end, or incorporating as many additional factors as are reasonable) and then seeing if they're close enough to call it okay. If a case exists where it's reasonable to use the full code formula and you're doing things on paper, you're just doing it in the case that actually requires all the factors.
Doing enough math to make sure you're not getting a catastrophic failure and that your numbers are reasonable, when combined with some degree of judgement takes very little time. Hell, proper checking generally saves time because you're going to catch things that would be difficult to fix in the field.
Also, nobody's including any of this in their calculation package. Generally, a calculation package is the minimum necessary information required to satisfy people that the code has been appropriately applied and adhered to and that some degree of due diligence has been done. Additional information is confusing and takes time to prepare. I'm not going to write paragraphs in my checking calcs or my preliminary calcs to ensure it's clear to a code checker what my assumptions are. I'll write in simplified explanations that would make sense to another engineer that took a proper look at them, but anything more than that's a waste of time.
This is ignoring the things I'll do entirely by hand because it's just faster that way.
RE: who doesn't use manual computations anymore?
Any good engineer will perform a reality check but whereas you used to do it to confirm the provisions of the code now you do it despite them. For example, how many engineers simply apply a 20 psf (or whatever) wind load and design the structure vs. pouring through all the gyrations the code requires? Plenty, I bet.
And yes, some software providers do indeed include code provisions in their packages...in fact, I think most of them do at this point.
And no, I'm not a young engineer any more so it's less of an issue for me...I've watched a lot of these things morph into their current Frankenstein-like forms so I've been able to absorb many of them one step at a time. But I feel bad for the recent graduates. I've seen some that I think would have made good design engineers but were too intimidated by it to try and instead migrated over to the project management side of the house. It amounted to a loss of good talent due to code intimidation. A shame, really.
RE: who doesn't use manual computations anymore?
I'm going to avoid going into it more than that, because we've all seen what happens to threads where we start the 'codes are too complicated' conversation :p
RE: who doesn't use manual computations anymore?
RE: who doesn't use manual computations anymore?
I guess I'm too new here to have seen the 'codes are too complicated' threads; maybe I'll do a search for them...
RE: who doesn't use manual computations anymore?
Don't confuse code compliance with design. Never the two shall meet. But all too often, designers think "it meets code, so I'm done."
RE: who doesn't use manual computations anymore?
Oh, you needent worry that I will confuse the two; in fact, that speaks to a point I made on the thread related to the New Zealand earthquake thread in that an argument can be made that building codes reduce our safety rather than enhancing it.