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Re: Steelstud Shearwalls with Structural Panels

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Fasteners in steel studs perform quite a bit differently than nails in wood
studs. 

Wood nails tend to be fixed in bending just below the face of the wood stud
and absorb much of their energy by bending. Wood nails can still have
significant residual stiffness even after many cycles of bending. 

In contrast, fasteners in steel studs will rock in their holes and tend to
rotate at the face of the stud after a few cycles as if they are pinned.
(Hence its important to use fasteners with deep threads so they don't just
ratchet out of their holes.) There is very little residual stiffness due to
low fastener bending resistance at the face of the steel stud in subsequent
cycles. 

Fastener stiffness picks up with extreme lateral loads, but this is primarily
due to fasteners being pulled in tension by panels rather than fastener
bending at the face of the studs as in wood systems. 

When earthquakes and their aftershocks are over, and if you have small
residual offsets in a steel stud system, you can expect relatively low
residual wall stiffness compared to wood studs. Walls with large permanent
offsets will likely have large stiffnesses in the direction of the offset and
very little stiffness in the opposing direction. 

While this might not be life threatening, steel studs could result in a
different type of property loss than we normally see in wood frame systems.
How much more or less loss? I don't think we have enough information to know,
but my hunch is there could be significantly more property loss in steel
stud/panel systems because of the low residual wall stiffness in some
building locations for certain types of ground motions.

Fred Turner
Staff Structural Engineer
Ca. Seismic Safety Commission
1900 K St. #100 Sacramento, CA 95814
916-327-1606 916-322-9476 Fax
FredT5(--nospam--at)aol.com