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CSA O86 allows for shear walls to be designed to resist overturning using either hold-down connections or anchorages at the ends of each shear wall segment. A complete description can be found in Chapter 9 – Shearwalls and Diaphragms of the CWC publication Wood Design Manual. The software allows for shear wall design using hold-downs and/or anchorages.
A lateral force acting on the top plate of a shear wall segment tends to overturn the segment. To resist this overturning force, traditional shear wall designs include hold-down connections at the end of any segment subject to overturning. A hold-down connection normally consists of steel brackets, anchor bolts and/or a threaded rod connecting the tension end-stud of the shear wall segment to either the foundation or to a lower level shear wall (refer to figure 9.7 of the Wood Design Manual). If hold-down connections are included in the design, the overturning force is transferred from the top chord directly through the tension end-stud (and then through the hold-down connection) to the wall or foundation below. Since the sheathing is not used to transfer the overturning tension-force, all of its strength can be considered for shear resistance.
Anchorages may be provided, as an alternative to hold-downs, to resist the overturning force acting on a shear wall segment. An anchorage is a threaded rod, installed within 300 mm of the segment's tension end-stud, connecting the bottom plate to the foundation or to the top plate of a lower level shear wall segment (refer to figure 9.8 of the Wood Design Manual). Since the tension end-stud is not directly tied down, the overturning tension force must be transferred through the sheathing. The full strength of the sheathing, therefore, cannot be considered as contributing to shear resistance. To account for this, CSA O86 requires that a hold-down effect factor, Jhd, be applied to reduce the design shear strength of shear wall segments for which anchorages are provided instead of hold-downs.
Refer to Hold-downs Effect Factor Jhd for more information about the shear wall design implications.