The SEAINT List Server has been down, and I'm not sure that the following
message, sent during the down period, got through. It deals with a concept
that I haven't seen or heard discussed, and I would like to be sure that it
is on the table for consideration by the SEAOC Seismology Committee.
I believe that Ben's and Ron's points regarding diaphragm yield are both
valid, each applying to different types of structural systems.
If yielding of the diaphragm results in damage to a gravity-load-carrying
component of the system, as would be likely to be the case for a concrete
diaphragm, the design needs to protect the diaphragm from yielding.
If the yielding of the diaphragm would not damage the gravity-load-carrying
system, as would most likely be the case with a wood-sheathed diaphragm, the
diaphragm may be the most appropriate part of the lateral load resisting
system in which to allow first yield.
This is another case showing us how importance it is to have reviewed by
engineers experienced in each type of structural system the proposed Code
provisions that are intended to apply to all kinds of structural systems.