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RE: OMRF (R value) (code development process)

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Mark,

I believe that was part of Charlie's point.  I believe he was trying to
point out that the R-factors _COULD_ have been "...based upon actual,
observed and test performance...", but there are more influenced by
subjective criteria even though they do in a VERY rough way reflect real
performance.

Actually, I know for a certainty that the selection of R-factor is rather
arbitrary.  I was present during the discussion of what R-factor's seemed
logical for the new precast special moment frames and other new systems at
the Seismic Subcommittee H meeting of ACI 318.  While the R-factor for
these systems have some basis in real performance relative to other
systems, actual values (i.e. 4.5 vs 5 vs 5.5 etc) are purely subjective.

I believe that Charlie's point (and your's) is that we should have an
objective system which would set the R-factor based upon testing data of
lateral systems.  This would make sense to me as well, because then that
testing system could be made into an ASTM procedure and used by
individuals if they have a lateral system that does not quite fit into any
of the systems in the code.  I am confident that this could be done, but I
am sure that there are some technical hurdles as well as political hurdles
that would need to be over come.

HTH,

Scott
Ypsilanti, MI


On Sun, 14 Jul 2002, Mark Gilligan wrote:

> 
> With regards to the R factors being "...based upon actual, observed and
> tested performance...",  I would suggest that you take that statement with
> a grain of salt.  In reality the R factors were calibrated to the arbitrary
> K factors that were previously used.  There was some tweaking of specific
> values but in most cases the values were more influenced by the opinions of
> the delegates than they were by any formal process.  I seem to remember
> hearing of a research project by ATC that was supposed to develop a formal
> methodology for determining R factors.  The fact that we still do not have
> a formal procedure for determining R factors would suggest that all of the
> R factors are at some degree subjective.
> 


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