Return to index: [Subject] [Thread] [Date] [Author]

RE: Who's using ASD or LRFD?

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Title: RE: Who's using ASD or LRFD?

>I'm left with the very strong impression that this isn't so much new
>methodology as the old methodology tarted up with a new vocabulary. Seems
>like we engineers do that a lot.

You're both right and wrong on this, Chris. No insult intended with the latter half of that statement.

At the starting point (circa 1986 when LRFD was first released and that Essentials of LRFD publication you mentioned was written) there wasn't all that much different between LRFD and ASD. They came from the same basis (which is why I wonder whether people that say LRFD is so wildly different from ASD have actually even looked at LRFD). I'd say the major difference at that time was the more uniform treatment of load variability for the wide variety of design loads.

Since then, there have been two revisions of the LRFD Speciication: the 1993 revision (in print) and the 1999 revision (being finalized right now). In each of those revisions, a little more has been added that differentiates LRFD from ASD. The 1999 LRFD Specification will have, among other things, explicit treatment of srength and stiffness requirements for stability bracing for beams, columns, frames, etc., a section on evaluation and load testing of existing structures, and a major improvement to fatigue provisions.

You're right too that we engineers do all like to change our vocabulary all the time.