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Re: We're Not Getting Older, We're Getting DUMBER

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On Jan 25, 2006, at 11:17 AM, Scott Maxwell wrote:

Point is that I agree that there are quite a few engineers that are more than happy to bury their head in the sand and conintue to use what they are used to using even though there is new and typically better knowledge (or codes) out there.
I swore I'd stay out of this, but I can't help myself. This thread is only half a discussion--a lot of people saying 'newer and better' but no one saying what's improved. Could someone please tell me what's the improvement with limit design? Are fewer buildings collapsing than before? Is the owner's cost noticeably smaller? Are structural design fees going up? Or down? What's been gained by changing our jargon to include 'limit state?' So far we know that academia loves it and so does Canada. New graduates seem to like it but they're taught nothing else, which isn't much of a reason. Anyone know why they teach it instead of ASD? Can anyone cite any examples of hazards avoided? Are buildings built under ASD design rules being scrapped because they're dangerous or unsatisfactory? Any correlation between seismic resistance and the code rules? It is suddenly easier to determine loading or characterize plastic collapse?

As an old fart who's gone from slide rule design of pressure vessels in the 60's to FEA I've seen some real Code changes and the improvements they led to. The most profound was a realistic consideration of fracture toughness in design and the second set out an analysis-based design approach which allowed lower design margins in return for greater attention to secondary stress and fatigue. Both of these embodied significant performance and safety enhancement that everyone could point to. And like LRFD, they still haven't been universally embraced or understood, even as Code provisions are being regularly upgraded. So I think I understand the process and the reasoning as well as anyone. Let's have it--why is LRFD an improvement? Will there be fewer bodies or do people like it because some academic told them to like it?

I've said a hundred times on this list that I don't do buildings, so maybe I've misunderstood something. In the years we've discussed the topic I haven't gotten much of an explanation of why LRFD is better--maybe this time it's different. It's been repeated a hundred times on this list: steel doesn't care what the design rules are--it always behaves like steel. Charlie Carter pointed that out a couple of days ago, and he's right, but there's still this undercurrent in this whole thread of shifting paradigms and 'better' designs, along with snickering about old farts who who stick with what works, just because it's what has worked, tee-hee.

Christopher Wright P.E. |"They couldn't hit an elephant at
chrisw(--nospam--at)skypoint.com   | this distance" (last words of Gen.
.......................................| John Sedgwick, Spotsylvania 1864)
http://www.skypoint.com/~chrisw/


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