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For each material type, the table below lists the maximum allowable aspect ratio h/b, where , b = segment length and h = height of segmented or perforated wall segment or FTAO pier, and the Shear Capacity Adjustment factor for walls or segments with high aspect ratios.
The areas of the program where you can see these aspect ratios and factors are given below the table.
Aspect Ratio Shear Capacity Adjusment Factor
For blocked wood structural panels and fiberboard, "unadjusted" values are given for the maximum aspect ratio for which no adjustment is necessary, and "adjusted" values for the the absolute limit. For wall segments between the unadjusted limit and the adjusted limit, the Shear Capacity Adjustment must be applied to the shear capacity.
For segmented and FTAO walls made from wood structural panels or fiberboard, as per SDPWS 4.3.5.5.1, adjustment factors are different according to whether you have selected capacity-based or deflection based force distribution methods in the Design Settings.
For perforated walls, the factor shown is not referred to as the Aspect Ratio Adjustment per se. It is an effective factor implicit in the SDPWS Eqn. 4.3-5 for perforated wall shear capacity. It does not depend on the force distribution method.
Non-shear-resisting Segments
In Segmented walls, segments that have aspect ratios that are are greater than the maximum are treated as non-shearwalls and do not attract shear force. .
FTAO piers greater than the maximum are rejected when you make a user interface change that would create one.
For perforated walls, segments greater than the maximum that occur at the ends of the wall, are neglected in the definition of the perforated wall, along with adjacent openings.(More than one set of segments/openings can be neglected at each end). Narrow segments interior to the wall are not included in the Sbi or Sb values representing adjusted and unadjusted lengths of full height sheathing.
Aspect Ratio Limits and Factors |
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Shearwalls |
SDPWS |
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Wood Structural Panels |
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Maximum aspect ratio |
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SDPWS 4.3.3, Table 4.3.3 |
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Blocked, adjusted |
3.5:1 |
3.5:1 |
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Blocked, unadjusted |
2:1 |
2:1 |
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Unblocked |
2:1 |
2:1 |
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Shear Capacity Adjustment* |
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4.3.3.2, 4.3.5.5.1 Exception 1. |
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Capacity-based force distribution |
2b,/ h |
2b, / h |
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Deflection-based distribution |
1.25 - 0.125 h / b, |
1.25 - 0.125 h / b, |
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Fiberboard |
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Maximum aspect ratio |
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SDPWS 4.3.3, Table 4.3.3 |
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Adjusted |
3.5:1 |
3.5:1 |
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Unadjusted |
1:1 |
1:1 |
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Shear Capacity Adjustment* |
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Segmented or FTAO walls* |
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4.3.3.2, 4.3.5.5.1 Exception 2 |
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Capacity-based force distribution |
0.1 + 0.9 b,/ h |
0.1 + 0.9 b,/ h |
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Deflection-based distribution |
1.09 - 0.09 h / b, |
1.09 - 0.09 h / b, |
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Perforated walls** |
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All types of force distribution |
Sbi /Sb; bi = 2b/h when h/b > 2 |
Sbi /Sb; bi = 2b/h when h/b > 2 |
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*Applies to shear wall segments with aspect ratio between 1.0 and 3.5. |
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**Fiberboard is only allowed in combination with wood structural panels on perforated walls |
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Lumber Siding |
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Maximum aspect ratio |
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Table 4.3.3 |
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Horizontal, Vertical |
2:1* |
Doesn't say |
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Single Diagonal |
2:1 |
2:1 |
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Double Diagonal |
3.5:1** |
Doesn't say |
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* Use value for single diagonal in absence of guidance for horizontal and vertical lumber |
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** In absence of guidance, use value for wood structural panels |
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Gypsum and plaster |
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Maximum aspect ratio |
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4.3.3, Table 4.3.3 Note 2 |
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Unblocked |
1.5:1 |
1.5:1 |
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Blocked |
2:1 |
2:1 |
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Plan View
The program shows segments as greater than the maximum aspect ratio as hollow, as if they were non-shearwalls. Segments to which an aspect ratio is applied are shown with diagonal hatching.
Elevation View
The aspect ratio and any applicable aspect ratio factor > 1.0 are shown on each wall segment in Elevation view.
Wall and Shear Line Dimensions Output
The Wall and Shear Line Dimensions table of the Design Results output shows the aspect ratio of all segments
Shear Results Output
The program shows the Aspect Ratio factor in the wall segment row the Shear Results table in the wall row in the column Cub/Asp.