Why did they do that? 19

[TehMightyEngineer]

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.

 

[msquared48]

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

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

Mike McCann
MMC Engineering

 

[TehMightyEngineer]

Does an E6B flight computer from my pilot training count?

Maine EIT, Civil/Structural.

 

[Agent666]

Calculators run on batteries these days Mike

 

[NOLAENG]

@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.

 

[TehMightyEngineer]

"I'm curious to know if the pressure to go from the design phase to build phase was as demanding "back in the

http://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.

 

[msquared48]

Agent:



Mike McCann
MMC Engineering

 

[TehMightyEngineer]

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.

 

[mtu1972]

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

 

[Agent666]

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

 

[3DDave]

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-have-toppled-an-nyc-sky-1564732214/all

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.

 

[hokie66]

http://en.wikibooks.org/wiki/Professionalism/William_LeMessurier_and_the_CitiCorp_Building

This is probably a better version of the Citicorp Building story.

 

[Agent666]

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!

 

[paddingtongreen]

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