Eric, thanks for your response. I think I am still missing a concept
though. You are right in that the yield curvature is lower if use use
lw instead of C`u, this is the problem. If the yield curvature is
lower, then the calculated total curvature is lower (ult curv = YIELD
CURV + plastic curv). If the ult curvature is lower, I am less likely
to need B.E. I have some books in my office, and will review this
concept again Monday. But it looks like my answer is this - the UBC is
interested in the max compressive strain (conc.) The side effect of
using Ec/C`u is that if the wall goes inelastic at all (Delta M > Delta
y), then you are required to have boundary elements. Numbers might help
better explain. I will try another post later.
Again, Thanks for your help.
Jake Watson, E.I.T.
Salt Lake City, UT