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Maximum Aspect Ratio
As per SDPWS 4.3.5.2 and 4.3.4.4., each central pier (i.e. between openings or between opening and wall end) must conform to the height-to-width limitations given in Table 4.3.4, that is, 3.5:1 for blocked walls and 2:1 for unblocked walls. These limits are not applied to opening piers or corner piers, however, these piers do not typically have high aspect ratios.
Aspect Ratio Factor
Although it isn’t explicitly stated in SDPWS 4.3.4.4, we were informed that the intention of the SDPWS is that force-transfer wall central piers that have height-to-width ratios between 2.0 and 3.5 are subject to the Aspect Ratio Factor given in 4.3.4.2 (for deflection-based distribution to segments), and the adjustments in the Exceptions to 4.3.3.4.1 ( for capacity-based distribution).
These are the same factors and adjustments used for segmented wall full-height segments, except that for force-transfer walls they applied to the dimensions of the central piers between two openings or between an opening and the wall end.
The aspect ratio factors are not applied to opening piers or corner piers, however, these forces rarely govern force transfer wall design, nor do they typically have high aspect ratios.
Width-to-Height Ratios
SDPWS provides only height-to-width limitations, asin ordinary shear wall segments, width-to-height is rarely an issue. However, for force-transfer walls, narrow piers above openings can have very high width-to-height ratios such that they cannot be relied upon to transfer shear forces. For example, using our 1-foot pier height limitation, a 4-foot opening exceeds the 3.5:1 width-to-height ratio.
In the absence of design code guidance, Shearwalls does not check pier width-to-height and leaves the design of openings to your judgment in this regard.