that stands on 14 foot steel tube columns concentrically brace. The
connections are butt welded to the columns.
These brace connections are not allowed in this seismic zone for new
construction.
The two story wood framing can be analyzed as though its base is at the
top of the steel braced frame.
Is there any concept or code that would prevent me using the flexibility
of the wood to isolate the braced frame from the otherwise high shear
loads due to its rigidity?
I am considering the Nonlinear Static Procedure (NSP) in the ASCE 41-06
"Seismic Rehabilitation of Existing Buildings". My thought is that there
is virtually no weight laterally and rigidly attached to the rigid steel
frame. The horizontal and vertical wood diaphragms will absorb energy
and possibly reduce seismic forces that would otherwise buckle the
braces and fail the connections. The connections then might not require
to be cut back for new steel gusset plates that would allow some yielding.
Otherwise I might consider this a voluntary upgrade and reduce the
criteria to a level that the owner can afford.
David Merrick, SE
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