Complexity of Engineering 19

[vmirat]

Recently, I received the latest edition of the Steel Design Manual from AISC. While purusing through the pages of this weighty tome, I reflected on how complex the field of engineering, specifically structural engineering, has become over the years. The respective institutes, societies, and such have spent lots of time and money developing more and more exacting methods for determining forces on structures. I'm wondering if we are getting to a point of diminishing returns? The more complex we make the process, the greater the chance for error. We develop computer programs to help us solve these complex problems but at the same time don't trust them. Are we to the point of "measuring with a micrometer, marking with a crayon, and cutting with a chainsaw?" And then I thought about the entire construction process, of which we are only a part. What about the builder? There was recently a very long post concerning additional certification for Structural Engineers (SE) based on the premise that the structural world is so complex that addition qualifications are required to insure quality. But what about the builder? Should there be additional qualifications for those involved with the building of these structures that we spend so much time and mental energy designing?

 

[DaveVikingPE]

FAR out!

If you want to make money, be an 8-A contractor!

 

[DRC1]

I think it is important to understand that structural engineering has not changed, only how we attempt to model and predict beam response to load. The actyual response of the beam is ignorant and uncaring of our predictions.
I think in college we are taught to design to the absolute least weight for a set of given conditions. This is fine for mastering the concepts of analysis and design. Unfortuantely, nobody ever tells us at our last class that you never really know floor loads, joint releases, construction quality and a host of other alues that effect the data we have been "Given". The other great seceret that no one shares at graduation, is that the steel costs are the least expensive part of the structure and increase the size of the member is the most cost effective insurance you can buy.

 

[WillisV]

DRC1 - as Hardy Cross once said "strength is essential but otherwise unimportant."

 

[MotorCity]

A college professor of mine had it right: "The only design code engineers need to follow is Mr. Newton's. His code is quite simple, there are only 3 rules".

 

[swearingen]

And which one of those nice three rules deals with the pages and pages of code language addressing serviceability? F=ma is great, but F=ma with 7 feet of deflection does a structural engineer no good...

 

[miecz]

More and more often, at seminars explaining code provisions, the first questions always seem to be "what software is available to do all these calculations?" This phenomenon is especially prevalent at LRFD seminars. It seems as though the attendees (myself included) are so overwhelmed by the code provisions that they intend to rely on software to "meet the code", and have no intention (or hope) of digesting the material just presented. A dangerous situation, if you ask me. If the purpose of the progressively complicated code provisions is to increase safety, it is having the opposite effect.

 

[dik]

DaveVikingPE... I've been using limit states and plastic design for nearly 30 years... Other than simple spans (which I avoid if I can make them continuous) nearly all steel design is Plastic... good economy and fewer pieces to handle... Our's was the first class at university to use Ultimate Strength Design for Concrete... and we haven't looked back...

Dik

 

[rapt]

Maybe we should look at it from the other direction. Codes have always simplified a lot of design aspects because the calculation methods were too complex to do on a slide rule or abacus. Now we have computers which can do the calculations maybe we should use them and the simplifications can be removed.

unfortunately we then get the situation that jmiec points out where a lot of engineers use software because they do not want to learn the theory and assume the computer will do it all for them. Computers are calculators and the software available today and for the forseable future are and will be calculation algorithms, not engineers. The engineer still must understand the background, the logic and the expected results and use the computer to his advantage, not to replace him. And far too many do not. They see design as producing a drawing as quickly as possible. Doesn't matter what is on it as the computer produced it so it must be correct!

Engineers must accept that there is a need for continuing education and that does not mean how to push a go button on a computer program. Would you go to a doctor who was still practicing the 2000 year old Roman operation or health care methods.

 

[Dinosaur]

Many interesting points and counter-points. Bottom line is I think some of us are too smart for our own good.

An earlier comment sugested ultimate strength was first before working stress. In my opinion, that was before there was anything like structural engineering. In those days, designers were architects of buildings who relied on empirical evidence learned on the construction site. They didn't do anything like what we consider engineering calculations today.

The advent of the railroad industry was the impitus <sp?> for modern structural engineering because you couldn't just throw a bunch of material at the problem anymore. That caused us to learn about structural mechanics, stress and strain, etc.

Regarding the durability of Roman structures, it is all very quaint. Kill a few thousand slaves and let the world admire your engineering prowess! Please, give me a break. With their budget, I could build a few things that'll last.

Codes are necessary for defining the loadings otherwise we'll never get off square one. After that, it all comes down to capacity on one side of the equals symbol and demand on the other. I agree with the concept of applying a smaller amount of the factor of safety to dead load than live load. This is the single best element of LFD in my opinion. It could have been accomplished in WSD but would have left folks scratching their heads.

Likewise, plastic hinges, yeild line theory and all that is interesting, but becomes terribly cumbersome on multi-DOF systems.

In the end I have two substantial complaints about the current trends; we are getting less and less savy about actual construction and we are not getting paid more to go through the more complicated processes of LRFD but we have the same expectations and liability. I have reviewed other engineers work too many times only to discoved they didn't "know their sphincter from an excavation." Lets get back to basics and forget all this fancy stuff that inflates our egos.

 

[archeng59]

I worked am a former mechanical engineer (machine design). I changed to structural engineering because I wanted to be involved in something more creative. sorta "the grass is greener over there" concept. It amazes me that structural engineers spend a great deal of time analyzing buildings using rather exact dimensions for joint locations, member lengths and spans, member sizes, rebar locations, connection designs. However, the construction process is not nearly as exact. Appears to me the construction industry uses the "close enough for the girls I go out with" concept. In the machine design industry, if an engineer says something is not fabricated properly, things are done about it: whatever it takes to get the final result to match specs. The engineer is always right. In the construction industry, if a contractor builds something not exactly to specs, he does everything he can to get it approved and accepted. The engineer is not always right because "we all know engineers over-design everything", "that's the way I've always done it", or "I've never had to do that before". The contractor's opinion means more to owners than does the architect or engineer.

 

[miecz]

rapt-

Ironically, most engineers collect thier CEU certificates right after the questions about software are answered. (Notice that there are seldom many other questions.)

I'm afraid that Continuing Education may, if fact, be exacerbating the problem. Code commitees can make the codes as convoluted as they wish, and then use the complexity to justify a code seminar. The CEUs are offered as carrots to entice addendees, as we all need to show our licensing boards those CEUs. Because of time and budget restraints, the seminars are squeezed into an intensive session. The result, a complex code, a confused engineering community, and a call for more software.

Dinosaur-

Very insightful and well said.

 

[JStephen]

ArchEng- you remind me of the quote I read a while back (possibly on this website) about how the engineers could show the elevations to 8 decimal places "but we still have to build it with the big yellow bulldozers".

 

[trac]

The adage that "If it looks right, it is right" nowadays probably means that it has not been designed and/or comply with some (if not all) clauses of the new codes.
Trac

 

[DaveVikingPE]

You know, if Hardy Cross were still around, there'd be no need for them fancy computer programs.

 

[archeng59]

JStephen, do you agree with that statement to a certain extent? the methods we use to analyze and design are much more exact that the methods used to construct the building. The interns who work for me want to calculate loads to the nearest 1/2 pound, for a tributary width to the nearest 1/8" and size a beam using a span measured to the nearest 1/8". They do not believe me when I say you can have the load determined to the nearest kip and the span to the nearest 1/2 foot for most designs. Mostly because their professors demanded that level of exactness and because they can calculate to the 10th decimal place using calculators or computers. is engineering too complex? I agree with vmirat's statment that we are at the point of "measuring with a micrometer, marking with a crayon, and cutting with a chainsaw."

 

[IRstuff]

You simply think you're accurate, but that's a fiction based on the fact that you can carry 10 decimal places. You and the industry make gross assumptions about the statistical distribution of the performances of the materials you use, you make assumptions about the ability to ignore the equivalent details like the strength and location of each and every fastener and joint.

In the end, you have to throw in a factor of 2, 3, or 4 to ensure that want you've ignored or simplified won't come back and bite you.

The reason that you can then allow the cuts to have such wide apparent uncertainties is that you've sufficiently overdesigned the system to tolerate these uncertainties, AS IT SHOULD BE.

You're the guy with the 4-yr degree, training, and license. Would you really want a 100-story building's fate to depend on the accuracy and discipline of a guy who might not have even finished high school? The design complexity is incumbent on you because you're trained for it.

TTFN

 

[connect2]

Codes/research/technical comittees its an industry like any other at the end of the day I guess.
I don't mind the codes, it the continual changes that are time consuming. We deal with six different materials. Its a full time job keeping up, never mind the demand side of the equation and all those related changes.
Limit States Design, Allowable Stress Design the mechanics are still the same. Elastic or Plastic analysis not much has changed. 1st. order vs. 2nd order elsatic/plastic analysis Hardy Cross vs. a computer matrix program. I'll take the computer any time.
Recently the phi factor (material reduction factor) for reinforced concrete increased from 0.60 to 0.65. Recently we were at a job inspecting reinforcing, dowels and vertical reinforcing, contact lap splices in a shear wall, it would make your head spin.
Its amazing how many of the references still in the new codes refer to guys coming out of the 40's, 50's and 60's for the fundamental mechanics.
I don't think nearly enough time is spent on mechanics and basic structural analysis.
I have a problem with proprietory products and code compliance based on third party testing and approval based on some governmental authority checking of the appropriate boxes. This is a whole different level of acceptance and required understanding removed from codes and calculations.
Lots of good points in this thread.

 

[JStephen]

I tend to be an 8-digit person myself, just because so often, the work is done on computer anyway, and it's actually extra work to round it off, there.

On the overall complexity question, it seems to me like when a structure is actually built, stands a 100 years, and is then demolished, that there is nobody in the world that can say within a factor of 2 what the seismic loads are that the building will actually see during that time. That being the case, I can't see much reason to get beyond the 4-zone type of earthquake design.

 

[rapt]

jmiec,

I do not regard a seminar of any sort as contributing to continuing education. Just shows what a joke the whole system and the people who have risen to a psoition to run it are.

A good engineer will question what he does not understand and research it and improve himself. That is continuing education but we do not get many points for that. That is supposed to be the whole aim of our university education. Not to put out technicians who know which buttons to push. Unfortunately now a lot of universities are now putting out button pushers.

Anyone who does that research will understand the reasons why codes are becoming more complex (in many cases) and will learn the theory behind what we do and be better engineers for it.

The rest will just figure out which new buttons to push.

 

[vmirat]

Well. I never guessed this comment would garner such attention! It warms my heart to know that I'm not alone in my frustration. Now the hard question. What can we do about it? We have self-appointed committees (ACI, AISC, ASCE, etc.) that are telling us how to do engineering. Is it time to "rage against the Machine" or do we continue to sit back and let them dictate our profession? At this point, the model building codes like IBC have pretty much adopted what these institutes and societies say, and the building departments adopt the model building codes, with which we must comply in order to build. Who's applying the common sense test to all this codes stuff? Maybe we should form our own national organization called the National Organization for Practical Engineering (NOPE)? We could charge membership fees and have conferences in Vegas!

Although I'm being a little silly here, I suggest we all think about who it is that's telling us how to do engineering.