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Like perforated walls, force-transfer-around-openings (FTAO) walls as defined in SDPWS 4.3.2.2 are a wlls with full height segments at the ends and one or more openings within, and other full-height segments between the openings. Like perforated walls, they and like perforated walls they require hold-downs only at the wall ends.
However, unlike perforated walls, segments with openings are included in the distribution of shear force and contribute to wall resistance. And due to minimum segment lengths, narrow segments not meeting the height to width ratios in Table 4.2.4 are not allowed within the walls.
In FTAO walls, shear force is transferred around openings by steel straps and blocking, and distinct shear stresses are developed in each shear wall "pier" – rectangular areas beside above and below openings, or above and below other piers.
.As per 4.3.3.3, aspect ratios and aspect ratio factors apply to each pier rather than a full height segment
SDPWS Table 4.3.2.2 calls for a minimum segment width of 2', but after consultation with design code authorities, we apply a min. width of 18" (blocked) or 2 feet (unblocked),
An additional restriction imposed by Shearwalls based on a review of FTAO literature is 12" foot of material above and below openings (i.e. no doors).
Shearwalls rejects FTAO walls not conforming to any of the abovementioned restrictions if you try to input them.
These walls appear with square hatching in Plan View. They are evident in Elevation view via the shear forces shown at each pier, straps, and strap-blocking forces.
Refer to the following for more details: