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The total force on each shear line is distributed to the shear resisting elements according to the relative rigidity of the element.
The determination of this rigidity and other factors affecting shear distribution to are controlled by several Design Settings, as described below.
Rigidity for Shear Force Distribution
SDPWS 4.3.3.4.1 states that force must be distributed to shear resisting elements such that deflections on each element are the same, except that distribution to segments based on the relative shear capacities can be used if for all segments with an aspect ratio of between 2:1 and 3.5:1 for wood structural panels, and 1:1 and 3:5:1 for fiberboard, a penalty is applied to the design shear wall strength. This penalty is given in Shear Wall Height-to-Width Ratio.
Shearwalls therefore provides a choice between using deflection-based distribution and capacity-based distribution:
Deflection of wall segments, perforated walls, or force-transfer walls
If this option is selected the program will attempt through an iterative procedure to equalize deflections on the shear line by redistributing the shear force v to the shear-resisting elements until the deflections calculated are the same for all elements. Refer to Force Distribution to Equalize Deflections for more information about the methodology employed to equalize deflections.
Note that this method can increase design processing time due to the iterative procedures, and can result in many low-stiffness segments or sides of walls taking zero load, especially on lightly loaded shear lines. Under certain conditions, the mathematical routine does not converge and deflections are not equalized as expected.
Shear wall capacity (wood panels and fiberboard only)
If this option is selected, shear force is distributed according to the factored shear capacity of the wall or segment.
This results in uniform unit design shear force on all wall segments on the line unless there are variations in the capacity of these elements for the following reasons:
If this method is chosen, the program ignores the contribution to shear resistance and to stiffness from gypsum-based materials and lumber sheathing to comply with SDPWS 4.3.3.4.1
Refer to the Rigidity for Shear Force Distribution Design Setting for more information about these options.
Identical Materials and Construction
Using this setting, if you choose to allow walls on the shear line to have different material specifications, and have selected some unknown materials, an iterative design is performed with shear wall strengths or stiffnesses from one iteration leading to a redistribution of forces on the next, and possible different walls designed on the final iteration.
If all walls must have the same materials, for capacity-based design, only one force-distribution iteration is needed. For deflection-based design, fewer iterations are required if all walls are specified to have the same materials.