ASD vs. LRFD?
ASD vs. LRFD?
(OP)
I'm a young gun starting out his career, and my father (a civil P.E.) taught me how to do all my calcs using the ASD method. I recently bought Salmon & Johnson's "Steel Structures" 5th Ed. and they emphasize LRFD. Is this a trend that is starting to be used more and more? I'd like to know which method is more prevalent throughout the country (my guess is ASD), so let me know what you guys are using.
- Adam
- Adam






RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
ASD worked for 100 years --- so why challenge that??
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
LRFD is becoming more and more prevalent. Concrete is almost exclusively designed using LRFD.
Wood design has attempted to move toward LRFD, but is overwhelmingly designed ASD. (The newest specification is a dual format specification, similar to AISC 13th ed.)
I disagree with you mike; the whole point of having load factors is to account for uncertainties in a statistically significant manner. If your dead load is off by 10%, that's OK because you have factored your dead loads by 20%, etc.
In steel, LRFD and ASD are calibrated to give nearly the same results at a LL/DL ratio of 3. At Higher LL ratios, LRFD generally requires larger sections.
RE: ASD vs. LRFD?
I was taught LRFD in school. Went to work and had to learn ASD. Went back to grad school (while working) and had to re-learn LRFD. Went to a steel seminar on 360-05 and had to learn the LRFD equations again. No wonder why I get them mixed up from time to time.
Now with the new spec I don't think it really matters. Use what ever you think is easier.
Personally, I still use ASD. I think it's easier because you don't have to calculate a different set of loads to figure deflections.... and I don't have to explain everything to my older coworkers.
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
All of a sudden I feel like I should be wearing inappropriate amounts of gold. *sigh*
YS
B.Eng (Carleton)
Working in New Zealand, thinking of my snow covered home...
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
I use both methods, more often ASD, but occasionally LRFD for aluminum analysis.
RE: ASD vs. LRFD?
Did someone mention the school no longer teaches ASD? It's a surprise and disappointing decision. Not wise, at least for the time being.
RE: ASD vs. LRFD?
For steel and wood design, ASD makes sense because deflection generally controls. You use unfactored loads for design and you then check deflections using those same loads.
DaveAtkins
RE: ASD vs. LRFD?
*Pray to God it Works
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
If you have the experience to judge a deflection check may not be required, but many elemnets should always be checked for deflection.
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
In ASD, you factor one side of the equation.
In LRFD, you factor both sides of the equation.
Am I missing something??
RE: ASD vs. LRFD?
I think since you are young Adam, there is no reason why you cant learn and adopt both methods, either way it makes you are far more rounded engineer.
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
Your statement is true of the new ASD vs. LRFD, but not true of the old ASD vs. LRFD.
RE: ASD vs. LRFD?
RE: ASD vs. LRFD?
Keep in mind the old ASD is 20 years old and wasn't updated from the time it came out until 2005. The difference between the old ASD and the new ASD is merely better information, not a dramatic change in philosophy.
RE: ASD vs. LRFD?