significant moment frame. In this case the moment frame would provide redundancy for the
shear panel. If the diagonal straps fail, this moment frame capacity would provide lateral
resistance for the moment from the P-delta effect of the gravity load. This redundancy is critical
to preventing building collapse for a structure whose lateral load resisting system has failed. The
panel redundancy factor, 1 is calculated as follows:
Qu Qp + Qc
Qp = the portion of the shear panel ultimate lateral capacity carried by the primary lateral load
resisting element including the effects of strain hardening. For panels with full panel
sheet(s) this contribution will increase with increasing deflection due to a widening of the
panel tension field. This value can only be reasonably determined by measuring Q c (as
described below) and calculating Qp as the difference between Qu and Qc.
Qc = the portion of shear panel ultimate lateral capacity carried by the columns acting as
moment frames. For panels with full panel sheet(s) this value can only be obtained by
testing the same exact panels with the full panel sheets removed. If these tests are not
performed for full panel sheet shear panels, Qc shall be set equal to zero.
4. The width of the cyclic test load/deflection hysteretic envelope. If the hysteretic envelope is
significantly pinched (no or very little load resistance away from the peak excursions), much less
energy is absorbed by the structural system so that building amplification grows. Pinched
hysteretic envelopes occur when the primary lateral load-resisting element is stretched, and there
is little redundant capacity from other elements to pick up load, so that little resistance is available
away from the peak excursions of the load cycles. Panels with significantly pinched hysteretic
envelopes, can experience high acceleration impact loading because the building will be free to
sway with little resistance and then suddenly snap the lateral load-resisting element when another
peak excursion is reached. This high acceleration snap can cause brittle failures. A shear panel
with a great deal of redundancy within the panel, 1 will tend to have a wide hysteretic envelope.
based on data measured in the
Table F-5 defines the acceptance criteria in terms of , and
cyclic panel tests, as defined by Equations F-2 through F-4.
Table F-5. Acceptance Criteria for Shear Panels
based on , and 1.
Panel Redundancy factor, 1
Hysteretic Envelope Width
Values for the system response modification factor, R system overstrength factor, 0 and deflection
amplification factor, Cd, are defined in Table F-6. These values are used in the seismic design
guidance defined in TI 809-04 and FEMA 302. Exceptions to this criteria shall require Corps of
Engineers Headquarters (CEMP-ET) approval.
Table F-6. Values for R, 0 and Cd.
System Response Modification Factor, R
System Overstrength Factor, 0
Deflection Amplification Factor, Cd