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Re: asd vs lfrd

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Jon turner wrote:

> I was wondering why allowable stress design is still being used in
> the United States.  I am a practising structural engineer in Canada and have
> been using limit states design, which i believe is called lfrd in the US,
> since I graduated from university.  I do not have much knowledge about asd,
> so can somebody clue me in on the advantages and disadvantages between the
> two systems? Also I am wondering why you have so many exams to become
> registered as a professional engineer.  Here in Canada, after you graduate,
> you are registered as an engineer in training.  After a period of two to
> four years, depending on your province of residence, as an engineer in
> training you become a professional engineer after passing a civil law exam
> related to engineering.  Many people have told me the reason for the
> differences in our systems is that your engineering programs are not
> regulated from university to university, so the quality of students is
> judged more from whether they can pass the exams after they graduate.  Our
> engineering programs are regulated by a central body insuring that all
> students are taught the same courses and that all of our engineers are on
> equal footing.

It has nothing to do with the ability of the graduating engineering students.
All recent engineers can do lfrd design.
The problem is with the Boss.  In our case, I am the boss, and I don't want to
learn lfrd.  It is just a waste of my time.  I have been using working stress
for almost 25 years now, and it works just fine thank you.  If I am going to
supervise engineers doing structural calculations for me and put my stamp and
signature on their calc's, I need them using a design method that I am familiar

I know that it seems like we may never switch over to lfrd, but with time it
will happen as it did with concrete.  When I went to school we were taught both
working and ultimate methods for concrete.  My first job at Bechtel we used
ultimate strength.  At my second job, the boss had no idea now to do ultimate
strength method, and would not allow me to use it, so I used working stress.  At
the present time in our office, either method is acceptable.  I tend to use
working stress the most because I know it the best.  However, I am equally
familiar with both methods.

I suspect that as time goes on, lfrd will become more common, as the "boss"
becomes more familiar with it.