An independent review of the bases for the development of resistance f
actors found in the American Institute of Steel Construction's (AIC) 1
986 Load and Resistance Factor Design (LFD) Specification is provided.
The objectives of this paper are to critically evaluate claims found
in a recent paper regarding the validity of these factors, to review a
nd investigate the probabilistic approach taken in the development of
these factors, and to examine the implications for design. Considerati
on is given to the reliability levels associated with established phi
factors, as well as the implications for design of using a larger dead
-load factor than is currently used. It is shown that, while an analys
is of allowable stress design (ASD) criteria indicates little consiste
ncy with respect to relative safety for different load combinations, a
relatively consistent reliability (about beta = 2.6) was assumed in t
he development of resistance factors for steel beams in flexure. Final
ly. while improved methods for estimating dead load may be warranted,
an arbitrary increase in the dead-load factor may be overly simplistic
and result in excessively conservative designs.