huangyhg

lfd & lrfd
could anyone explain me the difference between these 2 methods??
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are you sure is not an asd vz. lrfd comparison what you are looking for?
asd allowable stres design = old method
lrfd load and resistence factor design = most recent method
in aashto, chapter 10 steel design, it has lfd,( load factor design). my thought, lfd and lrfd are alike. is it correct??

no, they are not alike.
in a very small nutshell, load factor design includes factors only on loads, while in lrfd factors are considered on both loads and materials.
aashto has an entirely seperate code for lrfd. it is very nearly night and day difference between the lfd code and the lrfd code.
who uses lfd?
here we use:
wood - asd
masonry - asd (lrfd for slender walls)
concrete - lrfd
steel - asd (old skool both gravity and lateral)
(lrfd/aisc-spssb97 (for lateral only on occasion)
oh, i am a building engineer, not bridges.
is transportation industry the only one using lfd?
hi, i'm new here...
i'm a canadian engineer (mostly buildings)
here we always use the lrfd method, which we call limit states design. even for wood and masonry we use lrfd.
awe72: i am in california. you guys are few decades ahead of us.
concrete design here has been strength for quite some time now. for steel, most engineers still use asd. although there are lrfd methods for masonry and wood, i dont know of anyone using them in practice.
lsd, lrfd and lfd are all based on factored up forces vs. element strength with possible variations. i am not familiar with canadian lsd and lfd mentioned in this post. i am guessing basic design philosophy is the same.
qshake: would you mind expanding a little further on your description of lfd and lrfd? thank you in advance.
before expanding let me just say that, here in the midwest, we use mostly lfd for steel and concrete structures. wood and masonry are asd. lrfd has not caught on here and of course the developer/owners in the private sector could care less what method is used as long as it is done on time, under budget and no change orders occur. in the public sector, there have been a few states that actually practice lrfd and some who've threatened to implement it but have not done so to date.
qshake: it sounds like you do buildings. for steel design, do you use aisc manual of steel construction lrfd, third edition? reason who i am asking is, here we don't talk about lfd. we call it lrfd. and prior to reading this posting, i thought it was the same thing but apparently not.
well, from my own experience, lrfd (or lsd here) gives you more 'things' to check compare to asd (we call that wsd - working stress design here).
we design masonry with asd before and it is quite simple and fast then lsd method, but most of the time it's always a bit over-design. the new canadian masonry code will remove the option of designing with asd and only consider an lsd design.
yes but i agree with qshake that the argument is only between us the engineers anyway. and yes, i never heard of lfd too , i got the impression that it's the same with lrfd. so, qshake, i'll be interested in reading some info. anything online that i can access (website, etc?). thanks
hello there awe72.
basic difference between wsd and lsd is that in wsd, we use the actual force a

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