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CSA O86 11.5.5.3, Figure 11.7 mandates that relative shear wall capacity be used to determine the distribution of forces along a shear line. However, the Commentary to O86 11.5 indicates that this method is not valid for shear lines with variations in materials, construction or hold-down configuration, and that distribution based on relative stiffness of shear wall segments is preferable. If the Use shear wall deflection the calculate rigidity Design setting is checked and Distribute forces to wall segments based on rigidity is also selected, the program attempts through an iterative procedure to equalize deflections on the shear line by redistributing the shear force v to all the shear wall segments until the deflections calculated with are the same for all segments.
Constant Components of Shear Wall Equation
It is not apparent in the form of the shear wall deflection equation, but shear wall deflection depends on a number of constant components of that are not dependent on the shear force v. These constant components are non-wood panel nail slip, the effect of wood shrinkage, bolt-hole tolerance, miscuts, and gaps on hold-down displacement, the hold-down force components due to dead and wind uplift loads and from hold-downs on the levels above, and hold-down overrides you can apply in the Hold-down settings .
This constant component has several effects on the procedure to equalize deflections, described in the subtopics to this topic.
Deflection in Sheathing of Two-Sided Wall
Before the deflections in shear wall segments are equalized, in each segment with sheathing on both sides of the wall, the sum of the sheathing shear deflection and nail slip deflection is equalized as described in Deflection of Two-Sided Shearwall.
Design Processing Time
As illustrated in Design Processing Time, the option of equalizing deflections can increase processing time needed to achieve a successful shear wall force distribution and design. Improvements to processing efficiency have reduced this time to manageable levels even if this method is used.