Need a book? Engineering books recommendations...

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

FW: LRFD Load Factors.

[Subject Prev][Subject Next][Thread Prev][Thread Next]
Dave,

You make a very good point.  The material factor phi was determined by
comparing the material strength and dimensional variations produced to meet
certain tolerances.  If the material is produced under conditions exceeding
the assumed tolerances, then phi factors should decrease to provide the same
reliability.  In lieu of local provisions, this is where engineering
judgement is used.

I have worked with British Standards and have noticed that they are very
similar to the American LRFD.  Someday, when we Americans master metric
units, we can all be working off the same page.

Thanks for your comments,

Curt La Count, P.E.
Jacobs Engineering
Portland, OR
 ----------

I think you are only right when dealing with a consistent set of codes and
this hasn't been expressly stated in this thread so far.  In New Zealand
for example, load factors and phi factors are different to Australia codes,
but when only one or the other is used both codes provide a similar design
and factor of safety (excepting earthquakes - lets not get sidetracked on
this example!).  Using the Australian loading standards in combination with
New Zealand material standards would not be correct.

I think load factors apply only to the code that are stated in.  A code
which has poorly defined loadings for say wind or earthquake would/could
 have a higher load factor to compensate and therefore be only applicable
when used within that code.

Material quality and more importantly construction quality DO vary around
the world.  I would expect material factors to vary on this basis alone.
 This makes me think that not only is it appropriate to use a consistent
set of standards for design, the construction specifications would also
need to be those developed around those same codes.  From personal
experience, it is difficult specifying local specifications in a different
part of the world where the industries there have there own codes or an
other country's code and are unfamiliar with the specified ones.

Regards

Dave Meney