As JAE pointed out, there have only been a few posts that actually addressed the OP's question. Since we've digressed I've decided that writing a haiku will be just as productive as arguing preference
Allowable Loads
Resistance changing Designs
Factors our Stress now
Well, his question was, "What method is most economical and safe to use in the design of steel structure, is it LFRD or ASD?" (With emphasis added.)
Several people addressed the economics of it and Ron addressed the "safe to use" issue. As he pointed out, ASD is less susceptible to user error and surely that's of consequence to those of us who are highly susceptible to such...
Here's my haiku:
Dead load plus live load
equals total load. Unless
factors phi it up.
Archie: Yep, I can't think of one reason that makes LRFD safer than ASD except perhaps that one could make a mistake going from an ASD steel design to LRFD concrete design, but that's all I got.
That said, if you look at the original question saying "what method is BOTH the most economical AND safe to use in the design of a steel structure..." I would say LRFD would be the answer. It is safe as far as I can tell. Maybe not "safest" but it is safe. It's also the most efficient unless you have a very large live load relative to your dead load. Thus, I would say the only reasonable answer, however against the grain it is, would be LRFD.
I just like to keep it simple, both in the design approach and the construction. Complicating anything increases the possibility of errors. Errors increase costs too. ASD over LRFD. I will be quiet now...
