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Why did they do that?
19

Why did they do that?

Why did they do that?

(OP)
Working under a PE from the red book era of AISC I often see aversion towards "modern" methods of doing things. It made me wonder what people thought of engineering then (before my time) and now. Basically I'm looking to get perspective from other engineers on what they like or dislike about modern methods vs "back in my day" and find out why people think engineering has made the changes they did.

Speifically, LRFD vs Allowable Strength Design vs Allowable Stress Design. Green book AISC vs black book. Hand calcs vs computers (i.e. effective length vs direct analysis). Simple equations vs complex equations.

If you're wondering, this was brought on by my boss and I discussing how the green book has you check base metal at the weld fusion for a fillet weld but the black book does not. We also often have discussions on the merits of ASD vs LRFD load cases. For example, is it unconservative to design a buried concrete structure for LRFD load cases when it's all dead load.

Maine EIT, Civil/Structural.

RE: Why did they do that?

I am curious what we have to say about this one. I know my office we have some people who still exclusivly use ASD for everything but large Seismic and some special concrete design.
-
I have almost always been told that ASD is more conservative than LRFD and has simpler equations. the simplicity stems from more conservative curve fitting(?). I suppose to me it is a thing of doing what one is comfortable with, and why would 20 years of ASD knowledge be replaced with 0 years experience of LRFD. I can see that as a difficult transition to make a Senior Design Engineer do.

RE: Why did they do that?

Black book still has that. Sort of. . . . Page 9-5 (of the manual, not the spec) has a section about base material rupture at welds. Essentially saying that the base material has to have a certain minimum thickness to avoid base material failure.

If not met, in my calcs, I use this to reduce the strength of the weld connection down to a value that will match the base material rupture.

RE: Why did they do that?

(OP)
Josh: Yes, that's the conclusion we came to as well in our office and elected to use either that or the 9th edition base metal fusion check.

Maine EIT, Civil/Structural.

RE: Why did they do that?

6
Speaking only for myself, I don't like:
  • Complications for complication's sake
  • Feeling like I have to rely on a computer to get to a solution
  • Rube Goldberg load factors so that I can design to within a gnat's whisker yet still have to wonder if I've done it correctly
  • Getting lost in the forest for the trees (i.e., feeling so bogged down by the code updates that I wonder if the building will pass muster with the code officials when I know it will stand up to the forces of nature.)
  • The implication that the old-timers were a bunch of ignoramuses who couldn't design a building now that we have our nifty new codes
  • Feeling like I'm at the mercy of the theoreticians
  • Being distracted by minutia causing me to miss the larger principles
  • Feeling like we're getting away from the wisdom, elegance, and simplicity of our forebearer's designs for too-clever-by-half "sophisticated" solutions that might prove to be penny-wise and pound-foolish
I could go on but I'll confine myself to that for the moment. But, hey, you asked.wink

RE: Why did they do that?

(OP)
No, no keep going Archie. As a young and impressionable engineer (Hah!) I not only want to know what you think and actually agree with you on many of your points.

Maine EIT, Civil/Structural.

RE: Why did they do that?

I am glad to hear that I am not the only one who uses the t_min calculation to downgrade the capacity of my welds under the assumption that excess weld will not contribute but is present.

Archie, what do you like? :)

RE: Why did they do that?

Archie264:
You speak for me too. Nicely done.

RE: Why did they do that?

Yikes - another ASD vs. LRFD thread. Run. Hide. Stock up your shelter with toilet paper and scotch!

RE: Why did they do that?

(OP)
Well, I guess, but I probably wasn't clear on what I meant. ASD vs LRFD was merely an example which has been discussed to death. While I'd love to hear more about it I also was hoping people would discuss items similar to what Archie brought up; how we used to design vs how we design now and what they think of it.

In the end I'm basically looking for what people would reply to any engineer who says "I don't like how they do X now...", not "I don't like X because." Though obviously there is a lot of parallels between the two.

Maine EIT, Civil/Structural.

RE: Why did they do that?

Hmmmmn.


Seems like the "Build per Code" answers don't ever answer ..
Does it work?
Did it work?
Will it work? (Under this specific set of conditions, temperatures, maintenance, pressures, loads, movement, soil/building/steel/ground/wind/seismic/dynamic loads conditions?
What have I not allowed for?
What might happen, but not at the same time, have I allowed for that can be eliminated? (Do you really get an earthquake, hurricane and all those people climbing the tower at the same time?)
Is it safe now?
Will it be safe in the reasonable future?
Will it be safe under unreasonable (but foreseeable) conditions?

Can it be built at my client's budget, material, ability, material, labor, and time constraints+

RE: Why did they do that?

OK - sorry - Just seemed like the thread was taking that turn....

I can say that I have designed out of the red AISC manual. That said, I currently use LRFD. I can use both, don't really care that much about either. I understand how LRFD is more accurate in terms of probability of failure and also understand that in many cases that increase in accuracy doesn't amount to a hill of beans....but sometimes it does.

Back when I was a younger EIT, I did see a lot of the older engineers using "old" methods. One guy was still doing concrete design in ASD - so you'r talking perhaps 1950's era designs.

I think what I saw, and understood, was that people don't always feel comfortable with change

Think about yourself and how you react when your favorite word processing program or spreadsheet program gets updated.

People get comfortable with what they know and with their skill set. When new "stuff" comes along this can create a sense of threat - I suddenly don't know what I used to know or I suddenly aren't up to snuff with the latest code requirements - it can be un-nerving for an engineer who has successfully designed things for years only to be told that they aren't doing it right anymore.

RE: Why did they do that?

Yikes, I don't think I deserves stars for my whining, though I did mean every bit of what I wrote. (But thanks for them.smile) For me it's not so much an issue of ASD vs. LRFD but, rather, the overall increasing complexity that seems to be occurring across the codes and reference books. In my opinion the benefit from the continual changes and additions are well into the realm of diminishing returns and have become, in some cases, an impediment to good design.

RE: Why did they do that?

Archie:

If I could give you more stars, I would.

Sometimes I wonder if the code changes are due to the "nitch" effect, i.e., someone carving out a place in history for themselves.

If it ain't broke, don't "fix" it, especially by making it so complicated to decipher that more mistakes are far more likely as that moveable failure envelope is getting smaller and smaller!

KISS!

Sorry, but I guess I am into trite and hackneyed expressions today... Still very applicable though to me.

Mike McCann
MMC Engineering

RE: Why did they do that?

I learned to propose a structure to fill a need, then to visualize the loads flowing down the load paths, not unlike water down a pipe. I then asked each member (or group of similar members) questions, I asked if they were stiff enough and then if they were strong enough. As we investigated only primary load paths the structures had a level of redundancy. Very occasionally, I would perform a second order analysis but not often, I was discouraged by my bosses from doing so. Using load factors that applied to the whole structure was simple. As different load factors, and different strength reduction factors crept in it was discouraging, I could no longer "see" the loads flowing because of these multipliers and dividers got in the way.

I learned woodworking in high school, all with hand tools. Even though I have used power equipment since they do not feel comfortable. I spend more concentration on safety than on the shaping of the wood. Same thing with structural design, not having to worry about whether the model would run, or even having to tweaking it to make it run, left me free to understand the structure. Sorry if that sounds Zen but it is real.

I said in the first paragraph that the old methods left a level of redundancy, I understand that now we calculate secondary and tertiary load paths to the gnat's ass, we have to deliberately add in some redundancy. Because we took out, what to my mind was a natural redundancy, we have to deliberately and formally introduce an unnatural redundancy.

While we do use less material with LRFD, do we really save money, the material is the least of the costs of structures.

I would like to know if those of you raised on LRFD can "see" the loads flowing down through the structure to the foundations Whether you can see the structure bending a little, swaying a little.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

RE: Why did they do that?

You knows, many of the large buildings had wind tunnel tests performed on them during the design phase, many 20 or 30 years ago, and were placed in the skylines of the times. However, how many of these structures have been re-analyzed with the additional buildings around them today? How have the forces to the structures changed? Lessened overall? Locally increased? This is just the tip of the iceberg here...

To design these things to a knat's eyebrow just makes no sense to me when the rules are always changing. It's just too dangerous, and lives will be lost. Where is the redundancy, the fudge factor, the extra capacity, or whatever, to stand up to the unknowns of the future?

Mike McCann
MMC Engineering

RE: Why did they do that?

4
A different perspective (from a 1972 graduate):

I think the hand-calcs vs computer we see so often here is a false dichotomy. Sure you can get over-involved with detail and miss the big picture when using computers, but that can happen with blindly following a text book in a hand calculation too. Computers can be used as a black-box, but they can also be used to get a better understanding of how a structure really behaves than is possible with simple hand calculations, or to do a quick simplified analysis as an order of magnitude check on a more complex one.

As for allowable stress vs LRFD (or limit state design, as we call it in the rest of the World), I really don't understand some of the comments here. How does a procedure that only considers one condition (estimated stresses at nominal maximum loads) lead to a better understanding of structural behaviour than procedures that specifically requires you to consider the strength and serviceability of the structure under expected loads and maximum loads with minimum strength, and also to consider the stability of the structure under extreme loads, far in excess of the design loading?

Certainly it is possible to over-complicate the design process, but it is possible to over-simplify it as well. The question is not computer vs hand-calcs, it is how can we use all the available analysis and design tools most efficiently to produce the best end result?

We should simplify as far as possible, but no further. - Albert Einstein

Doug Jenkins
Interactive Design Services
http://newtonexcelbach.wordpress.com/

RE: Why did they do that?

The majority of errors that I have made in my designs were when I became distracted my some detail of the design that was not that important in the overall design and as a result I had less time to devote to the more important areas of the structure. I place the current codes in that catagory with too much time and attention devoted to minutia and squeezing the last ounce out of every detail. Every hour I spend trying to untangle the true intent of the codes is an hour less that I have to analize and evaluate all the more important aspects of the design. This is really a dangerous trend and is imposing on the practicing engineer unreasonable and impractical constraints while trying to ensure that the public is safe when his design is utilized.
Others have mentioned some real serious issues and specifically Paddington about redundancy.

RE: Why did they do that?

2
It is certainly not computers vs hand calculations, as computers have been a great tool. But in the computer era, the practice of structural engineering has been overly complicated, partly due to computing power. Because computer programs can be written to solve complex problems, creating complex problems is attractive, particularly to academics. Practicing structural engineers have not been sufficiently vocal or diligent in resisting complication for complication sake. If you just consider reinforced concrete structures, the last 50 years have seen moderate improvement in strength design, but not in serviceability. Problems of cracking and deflection, at least in my experience, are worse than ever. Some of this is due to accelerated construction practice, which the design codes fail to adequately consider.

RE: Why did they do that?

I don't understand why people focus on the code so much. Design shouldn't really be happening to the code. Code is a way to check at the end that you've met some minimum standard. Even then, it's really easy to use conservative factors in the code where you've sized things for other reasons and prove that everything's okay quickly.

I size 90% of my members to within 90% of their final size on the back of a piece of scratch paper. How I do my final documentation check doesn't really affect how I actually design things or slide loads around.

Whether it's LRFD or ASD or complicated formulas or simplified approximations it's all the same physical behaviour. If you have a reasonable understanding of that you're going to get to the same point.

A lot of the new code stuff just gives you more tools. Sure I've got a complicated interaction equation I can use for steel in biaxial bending with compression loads. I've got it in a spreadsheet and can use it if I have reasons to get that close to theoretical capacity. If I don't need to do that, in most cases I can still just add my three force/capacity percentages and if it's under 100% I know I'm okay and conservative. There are all sorts of fun complicated equations that you have the opportunity to use if you need to, but generally don't have to when you're in the 'figuring out the structure' stage.

RE: Why did they do that?

I think it's important to remember that any code is a minimum requirement... This applies whether it's fifty years ago or yesterday....

Our understanding just happens to be more complete in this day and age.

RE: Why did they do that?

Let me fix that for you...Our understanding just happens to be more INcomplete in this day and age.

RE: Why did they do that?

Not to distract from the direction of ASD vs. LRFD, but I have a problem with the complexity of the design codes in reference to seismic design. Is there a statistically relevant difference in the seismic factors just by moving a few miles one direction or the other? The new three or four significant digit lookup tools seem to think so. Is it not possible that the seismic zone maps were of acceptable accuracy? Perhaps going back to that system and updating the parameters would be a good compromise.

/end rant

RE: Why did they do that?

Some individual engineers understanding is incomplete because they see the codes of the day as the only thing they need to now satisfy. We all know there is more to structural engineering than satisfying equations, to understand how the structure works and behaves are some of the best qualities an engineer can possess.

Otherwise we know more collectively about engineering, the behaviour of materials etc than we ever have. This allows us to push the limit so to speak when we understand what we are doing.

Unfortunately in my experience the vast proportion of Structural engineers just don't get the basics anymore. Design is dumbed down by black box solutions that take everything to the limit where the feel for the design is lost. I am sure everyone has seen calculation sets that are just composed of spreadsheets with little demonstration of load path or even satisfying fundamentals like equilibrium.






RE: Why did they do that?

"Practicing structural engineers have not been sufficiently vocal or diligent in resisting complication for complication sake."

I don't think that necessarily the case. Computers has allowed architects to design structures that could previously only be dreamt about, since there was no way to do the math to even prove that the structure could meet its requirements. Asymmetrical structures were not easily analyzed, but computers can not make short work of them. Many of the taller buildings in seismic zones would have been impossible to design 30 yrs ago, because hand calculations would not have been able to model how active or passive dampers could protect the bulding.

TTFN
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RE: Why did they do that?

Agent666,
Now that you put it like that, I agree with you.

IRstuff,
I didn't argue about computers, but rather about unnecessary complication. The type structures you referred to probably involve 1% of our work, so should not be the tail which wags the dog.

RE: Why did they do that?

I am sure the pre-engineered metal building folks welcome ANY change in the code that will let them knock a few more pounds out of their spaghetti.

RE: Why did they do that?

Well said Archie and hokie66....similar era, similar thoughts.

As hokie66 noted, strength design is what it is, but serviceability has been woefully neglected. I understand that serviceability changes are on the cusp in the next couple of years (code-wise). Getting things to stand up is easy. Getting things to last is more difficult. Apply that as you wish!lol

RE: Why did they do that?

Ron,

Yeah, more changes!

RE: Why did they do that?

(OP)
Well, since not all changes are bad, who else is eagerly awaiting the new ACI code? About time they fixed that disorganized pile of lawyer dung. I can't believe it took them this long to realize that designing a column per ACI involes like 10 different sections in the spec whereas in steel or wood it's one freaking section (two or three if you count lateral stability and connections) and AISC and NDS include a manual for your troubles at almost the same cost!

Maine EIT, Civil/Structural.

RE: Why did they do that?

Does anyone have an example of LRFD giving less conservative results, and then problems from using the smaller size in the field? I see undesigned and drastically undersized components inexplicably work just fine. It is funny to tell someone that their 100-year-old beam is overstressed by 100% and needs to be reinforced.

LRFD is trying to respect the fact that things don't fail because they are 30% overstressed in ASD. Things fail when they are 400% stressed. Personally, deflection and serviceability mean more to me than a unity check. I see less experienced engineers super-concerned with strength and ignore deflection and vibration.

_________________________
TKE

RE: Why did they do that?

(OP)
Buried box culverts under AASHTO. City was using 3 rows of precast box culverts with end caps as underground storage tanks for combine sewage and stormwater overflow. Contractor placed one row and then excavated for the next placing the fill over the previous row (almost 200% the original soil load). No vehicle loads (too deep) so the engineer (not me) correctly designed them to a 1.35 soil load factor (vs 2.1 live load AASHTO factor) using the expected soil load. Note that AASHTO does not have a "dead load only" load case except for one that increases the self-weight of structures only. The box culverts were also cast with the wrong bar spacing by the precaster. Anyway, long story short they broke. Had they been done with a uniform safety factor they wouldn't have broken. We got called in to do an after the fact analysis and calculated that the bars were about at the expected yield stress if I recall correctly and that failure was ultimately caused by the soil overload and not the misplaced rebar.

Maine EIT, Civil/Structural.

RE: Why did they do that?

@TME
That's called experience!

RE: Why did they do that?

(OP)
Indeed. One thing my boss has taught me, and I've taken to heart, is very similar to what people have said here. Just because it meets the code doesn't mean it's good engineering. For example, we do a lot of work in industrial facilities and my boss never has me bring a column beyond 50% actual/allowable ratio if we can help it. Reason being that 50 years from now they'll probably hang 2 pipe racks off the column, want to add another floor, and bust up the flanges with forklifts. The key is to know what people are most likely to abuse and what they aren't. In an office building, sure, take the floor beams to 99%. However, don't put a custom lifting beam out there with the minimum weld required, it'll cost them a few dollars more to make sure the connection doesn't control and might save someones life.

Maine EIT, Civil/Structural.

RE: Why did they do that?

As a younger engineer, I would like to give me perspective even though this post was originally for more seasoned engineers.

Most of the senior engineers I work with would prefer to never use LRFD or the more complicated codes created only for revenue.
As someone who learned ASD, LRFD, finite element, etc. during college, I thought the senior engineers were just stubborn to change when I first started working.
Now, I often times spend too much time focusing on the potential load combination sets and factors (ASD - Steel, LRFD - Concrete, Service - Foundation) required for code prescriptions rather than the intent of a safe design.

After working for a couple years, I've come to realize that most of the basics and fundamentals of structural engineering have been lost in some ways with the advent of sophisticated computer analysis programs, spreadsheets, etc with my generation.
Some of my coworkers in the same experience bracket will often overlook things from a computer analysis or spreadsheet due to garbage in = garbage out.
I'm not saying we are doomed or I am an exception to the rule.
I still utilize the software tools available, but I've become much more diligent in checking them with hand calcs and common sense as I've gained increased experience.
Hopefully one day in my career we will reach common ground between fundamentals, computers, and methodologies.

As a black book engineer, please don't hit me too hard with your green/red one.

RE: Why did they do that?

(OP)
I've had the exact same experience uncblue. When I first starting out of college many of my designs were technically correct but looking back I focused way too much on doing every last detail and check in a design trying to "prove" it was "safe" where a simple, conservative back of the envelope calculation could confirm that and all the little details could be checked after I verified it with my envelope calcs. Forests and trees and all that. I've also found that I now do a lot more diligent in checking my spreadsheets and software with rough calcs. I've found a fair amount of my own garbage in = garbage out issues that should have been found much easier with back of the envelop calcs.

Definitely would love to see more younger engineers chime in here.

Maine EIT, Civil/Structural.

RE: Why did they do that?

2
Uncblue & TME:
For younger guys, I think you’ve got it right, and do see the trees and the forest for what they are..., This from an older guy. My hat’s off to you for this knowledge and understanding. None of us old guys are saying computers and software aren’t important. For all my ranting about the use of computers, computers and various software have allowed us to do things that we could only approximate or imagine before. In that, I agree with Doug and Hokie. They are a wonderful addition to our box of tools, in the right hands. But, they have also allowed way to many people who have little education or experience to pretend to be engineers, on things they have no business tackling, without some very serious and experienced guidance. Way too many of the users of this stuff have no idea how it works, or where the potential glitch points are in the programing. Most of this software tries to do way too much in one full swoop/or program, and consequently is pretty difficult to check or follow. The users have a very limited understanding of how the structure or detail works, which is actually caused by the very way they have designed and detailed it, so it’s pretty hard to imagine that they know how model it to get reasonable output. If it converges or it doesn’t blink in big red letters, ‘this’ll never work, you dummy’ they think they’ve got it right and they’ve done a good job. Never mind that the details can’t be fabricated or constructed.

None of us old guys are saying bldg. codes and standards aren’t important. But, the rate of change of all the codes and stds., with very little real improvement in the final infrastructure produced from these code changes; and the lack of coordination btwn. referenced codes and stds., and that pertains to content and date of issuance, certainly is no help to our entire industry. It is a hindrance, continuous headache, and very expensive, except for those who are enriched by the continuous publication and testing and research on so much minutia. I have never resisted an addendum or change when something really proved to be deficient in its current form, but change for change’s sake in dribs and drabs, scattered all over the place, mostly just confuses the process. There is no doubt about the comfort issue with what you know and use regularly. I taught WSD and USD in conc. back in the mid 60's, USD showed up and was used seriously for the first time in the ACI code. I have used many different steel codes over the years and followed the development of AISC’s LRFD with considerable interest. But then, by the nature of what I was doing, I missed regular practice with a couple cycles of the AISC codes, and have ended up behind the eight-ball ever since. I think I have a pretty good handle on the intent of all of the codes we use, but I’m becoming increasingly nervous about the rate of change and the minutia involved in that change, for the sake of change, which one could easily miss until he had to explain that code variation to a judge, in our litigious society.

It would seem to me that our educational systems are not teaching enough of the fundamentals any longer. That can all be done by computer, so who needs that fundamental understanding of how structures work any longer, a real feeling for how they work, that’s Paddington’s point. And, who cares about good clean design and simplicity of detail, the computer can handle the complexity even if we don’t know how to model it or check the results.

Mentoring seems to have gone out the window, we have the internet now, google it. Most of the OP’s here should be directed to the boss, so he knows what you know and what you don’t know, so he can make some effort to keep you and the company out of trouble. I’m all for giving a young engineer all he/she can handle, to force them to think a bit beyond their comfort level; but then watching and guiding carefully so they don’t go to far astray.

Good for you, I would like to work with you.

RE: Why did they do that?

(OP)
"Most of this software tries to do way too much in one full swoop/or program, and consequently is pretty difficult to check or follow."

My goodness, THIS! You made a bunch of good point dhengr (star for you!) and once this thread runs its course I hope to write up my impressions and summarize everything that was said here. That said, I definitely want to expand my personal experience on the above.

Back when I first started out of college I expanded a few spreadsheets I had created during college into design templates. The two most advanced were my wood beam/column spreadsheet and my foundation spreadsheet. The wood spreadsheet took input loads and sizes and ran through the bending and axial checks for a wood beam. While I never really had much I've changed in it over the years (still use both) if I were to make it today I would break it up into sections so that it's much easier to follow and much easier to utilize when I do something that's not very standardized (like a T-shaped wood column or something).

For the foundation spreadsheet though I've editing that thing about 10 times (most recently last week) and it's become this behemoth that can do rectangular footings, square footings, strip footings with unbalanced soil loads, wind and seismic moments at the base, etc. And I've still barely scratched the surface of what I could try to put into it. However, with my last revision just this week (added rectangular footing rebar calcs) I realized that it was very unwieldy. For example, I used it for a rectangular footing, great. But then when I used it for one that had a slightly different loading configuration it wasn't right and I had to re-write a bunch of load cases to make it correct. Tons of checking later and I was satisfied but I pity whoever in the office will be checking this because it's so convoluted now.

In the future I plan to be much more systematic with my calcs and my own spreadsheets. No "all in one" calculations (unless I'm doing something 10,000 times), rather one spreadsheet for one calculation. Then, if I'm doing something unusual, a hand calculation can replace one of my spreadsheets easily without throwing them all out.

I see the same thing you mention in software. They're so "all in one" that it's way too easy to screw up your inputs, way too easy to use something without having the experience to back it up, and way WAY too easy to misunderstand what the black box is doing.

"Good for you, I would like to work with you."

Thanks! That's very flattering.

Maine EIT, Civil/Structural.

RE: Why did they do that?

I think in parallel with 'improving' the codes, you also need to consider that the actual typical quality you get during the physical activity of building the structure from the typical contractor is usually follows a trend in the opposite direction...

RE: Why did they do that?

(OP)
Really what they should do is publish code revisions every 10 years or so that contain improvements to address any deficiencies (emergency code addendums could be added if needed). The remaining "new" material could go into non-mandatory addendums which get added to the code every 10 year cycle or so. MUCH simpler, much easier, much more practical. However, then we buy less codes... they gotta make their money somehow.

Honestly though, I'd take a $1000 code every 10 years than a $300 code every 3 years. Only once in the past 8 years have I ever wanted a new code because I wanted to utilize something "new" (GFRP bars in this case).

Maine EIT, Civil/Structural.

RE: Why did they do that?

Personally, I think the whole subject here should be termed "Code Blue". bomb

If you ever lost electricity, does anyone here still remember how to use a slide rule?

Mike McCann
MMC Engineering

RE: Why did they do that?

(OP)
Does an E6B flight computer from my pilot training count?

Maine EIT, Civil/Structural.

RE: Why did they do that?

Calculators run on batteries these days Mike :)

RE: Why did they do that?

@dhengr
I always enjoy reading the perspective of "older" engineers on this forum and learning from their wisdom.

"Never mind that the details can’t be fabricated or constructed"

I think this was one of the biggest learning curves for me when I began designing. I didn't learn anything about constructability during my school days and made some embarrassing mistakes along the way. Luckily the mistakes were caught in house, but they were definitely a humbling experience. I think universities should make a more concerted effort to teach this concept to students. I have been lucky enough to work mainly under two of the brightest and most mindful engineers imaginable. They have both been instrumental to my progress and understanding. To your point about litigation, one of the engineers in particular has always driven a concept into my head that has always stuck with me.
Could you reasonably defend your design to other professionals and officials?

@TehMightyEngineer
Cheers and I'm with you on the ACI Code.


Another item I forgot to list earlier was design turnaround. I'm curious to know if the pressure to go from the design phase to build phase was as demanding "back in the day" as it seems now. I feel the fact we have been able to do this in some cases due to software and computers has almost been a double edged sword. In my experience, now the clients seem to expect this all the time as if we punch in a few key commands and voila. The lack of respect for our profession compared to other similar professions (doctors, lawyers, etc.) is alarming to me when I look down the road of my career. We had a client moan and groan because he felt we were spending too much money and taking too long to analyze a very heavy lift (~50 ton). During one of the meetings, I was thinking are you serious? You do realize the consequences if this goes wrong? One of our senior engineers handled the situation diplomatically (another thing they don't teach you in school). In the end, the lift went very well and the hard working people in the field went home that day to their families which is most important to me.
I'll go homeless before I approve something with a guilty conscious just to keep my salary. Sorry for the rant but I'm interested in hearing what "older" engineers think.

RE: Why did they do that?

(OP)
"I'm curious to know if the pressure to go from the design phase to build phase was as demanding "back in thehttp://www.eng-tips.com/viewthread.cfm?qid=363449 day" as it seems now."

I'll second this, I'm sure it has but I'm wondering how people think it compares. I too have seen some lack of respect for what structural engineers do ("who cares if it can take the code prescribed loads, just have your boss stamp it already, we were behind when we found out it needed a engineers stamp."). That said, I've also worked with people who got burned because they didn't have a structural engineer, now they call us for all sorts of little things and provide us a reasonable amount of respect to our designs.

Maine EIT, Civil/Structural.

RE: Why did they do that?

Agent:

shocked

Mike McCann
MMC Engineering

RE: Why did they do that?

(OP)
They also can be powered by the sun!!

(Why the heck did the forum put a link in the middle of my post?)

Maine EIT, Civil/Structural.

RE: Why did they do that?

I've been enjoying this topic and had decided that I'd just be one more old-timer complaining about the new Codes, etc., and then uncblue touched on a topic I had not thought about in quite a while.

Working for a structural consultant on architectural projects in So. MI during the mid '70's, a review date would be chosen and everybody would print their drawings and exchange them. Arch., Struct., Civils, Mech., etc. Not sure the Elec. dwgs were given to us. Everybody would look at all of the dwgs to make sure everything was coordinated. After about a week the bosses/supervisors would meet again and exchange comments. Not only were any inconsistencies straightened out, but little things such as mis-spelled words or confusing notes would be brought to our attention. Having other sets of eyes reviewing the work was very valuable. Only then were the drawings finalized and issued for bidding and/or construction.

Don't know if this was common anywhere else, but over the last many years it seems that everybody wants everything ASAP.

And then the Contractor keeps a scorecard of RFI responses to flaunt any "delays" to the Owner, etc.

gjc

RE: Why did they do that?

When I do peer reviews I feel like I am doing that for them these days.

RE: Why did they do that?

Are "To Engineer is Human" and "Engineer's Dreams" by Petrovski required reading?

Also, came across this article yesterday:
http://gizmodo.com/how-a-simple-design-error-could...

It's about how a simple, code-acceptable design substitution led to a 1:16 probability that the Citicorp building in NYC could be simply blown over.

RE: Why did they do that?

It's always awesome that those who missed the obvious are charged with fixing the obvious, makes me wonder sometimes.

I have seen the opposite on a building our company peer reviewed, whereby it was square in plan, but Bracing was orientated on the 45 degree orientation. Engineers analysed it only in the orthogonal direction with respect to the plan. When they analysed the seismic cases parallel to the Bracing suddenly the loads went up 40 odd percent as expected.... Other than that it complied in full with the code!

RE: Why did they do that?

I may have given the impression that I'm against computers, not so, I was probably one of the first engineers to use a spreadsheet for engineering work, they were originally written for accounting purposes.

My first personal computer was the Sinclair ZX81. It was amazing what could be done with that 1k memory considering it included the display memory, there was even a spreadsheet, "VU-CALC" for it. My familiar with VU-CALC set me up to use Lotus 123 to speed up a huge piece of work and then the mainframe sheet for an even bigger one.

There are so many good points on this thread. To set the table on my contribution, so to speak, I started on the drawing board in 1952, when I was 17, in London, working for an American company designing and building oil refineries. I had one day a week to go to the technical college and started performing calculations a year later and on statically indeterminate structures the year after that. I don't remember which steel manual that was, I think it changed once during my ten years that company.

One of the things that made me leery of structural design programs was the difficulties we endured during their development, for a long time there were limited input options, preventing accurate modelling, and the results often were ridiculous. It was a souring experience and probably made me mistrust them for longer than appropriate.

As to the ASD Vs LRFD discussion, my view is that I have to check ASD for serviceability, why then perform another calc to simply reduce the weight of steel unless it produces a safer structure? Reducing the weight of members does not have a huge effect on the cost of members they need the same number of cuts and bolt holes and that is where the money is.

The thing I love about structural design programs is that if I exaggerate the scale of the deformation diagrams I can very quickly find what I did wrong, as long as there were not too many too many, the effect seems to grow exponentially with the number of bugs rather than linearly.

When I came to the USA in the mid sixties, the Portland Cement Association gave the concrete codes and manuals to us, PCA got a penny for every bag of cement that was sold, their job was to sell us on concrete structures. I think the AISC manual came free or at a reasonable price, I think they paid for the work, we paid for the printing etc. Now we seem to be the captive providers of a living for some academics and code writers.

Someone asked about schedule shrinkage. At the beginning of my working life, we completed the designs before obtaining bids on all disciplines; from there it has gone to, "How much can we shrink the critical path with incentive/penalty contracts?" to, "This is the schedule and these are the liquidated damages you will pay us if you fail."

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

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