Industry Practice for Steel Design
Industry Practice for Steel Design
(OP)
Hi,
I was wondering, if it is the current industry practice to use limit state for steel design or are you still using working stress (allowable) method?
I was wondering, if it is the current industry practice to use limit state for steel design or are you still using working stress (allowable) method?
Neilly Davies Consulting Engineers http://www.neillydavies.com.au






RE: Industry Practice for Steel Design
RE: Industry Practice for Steel Design
RE: Industry Practice for Steel Design
Neilly Davies Consulting Engineers http://www.neillydavies.com.au
RE: Industry Practice for Steel Design
RE: Industry Practice for Steel Design
RE: Industry Practice for Steel Design
If you "heard" it on the internet, it's guilty until proven innocent. - DCS
RE: Industry Practice for Steel Design
A pet peeve of mine is how people say "limit state design" to mean "LRFD." ASD is a limit state design, too. You check your loads to serviceability and strength limits. Where the factor of safety falls does not mean this isn't limit state design.
RE: Industry Practice for Steel Design
One of the hangups is that most of us tend to think in terms of stress, not load. Just one example is bolts. Regardless of size, if you tell me that a bolt has a certain tensile stress, I know whether or not it will be ok. When you tell me that a 2 1/4" A615 GR 75 anchor rod has 190 kips of load, it doesn't click with me whether or not it is ok. It's much easier to remember the allowable stress for commonly used bolts that it is to remember the allowable load for every given size. It's not that big an issue to calculate it but that's more time. And as everyone would agree, more time means more money and I don't see our fees increasing.
It's interesting to note how even with my limited use of the LRFD methods, I've found that deflection controlled my beam designs...which led me to a heavier beam...which took me back to something similar, though still slightly smaller, in size that I would have picked through use of AISC 9th edition. Also interesting to note is all the talk about "bouncy floors".
RE: Industry Practice for Steel Design
I'm an ASD guy, but I'll defend the groaning LRFD guys. The calculations are more lengthy not because it's LRFD, but because you're using a manual (green ASD) that is almost 20 years old. The new and improved methods result in more lengthy calculations. Blame that on progress, not LRFD.
RE: Industry Practice for Steel Design
RE: Industry Practice for Steel Design
I like to think in terms of where my loads fall in relation to a safe (allowable) stress condition. It just makes more sense to me than thinking in terms of comparing factored loads to an ultimate state condition.
RE: Industry Practice for Steel Design
RE: Industry Practice for Steel Design
You still need service loads for deflections. You can't get away from the service load combinations.
Surely you don't check drift with 1.6*50-year wind.
RE: Industry Practice for Steel Design
"The evolution of an Engineer begins with a passion for learning more and more about less and less until absolutely everything about nothing is known."
That said, LRFD brings us one step closer to our ultimate goal.
RE: Industry Practice for Steel Design
I would agree that serviceability is a unique case. Even if you used ASD, you would still have a separate load case for serviceability, as you have pointed out for wind. However, you could do wind with the LRFD factored loads by adjusting the allowable drift, depending on your local jurisdiction. Where I am at, there is no local code for wind drift serviceability, so I could offset the LRFD factored loads by setting the drift limit higher.
The point I was making was that you could do your steel design and concrete design using the same load combinations, especially when you get to foundation design.