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This is the wood shrinkage that occurs between fabrication and in-service of the perpendicular-to-grain wood members spanned by the hold-down.
It is calculated when the hold-down does not include a shrinkage compensating device.
Calculation
The vertical shrinkage displacement is 0.002 x (% fabrication moisture content – % in-service moisture content) x shrinkage length for the building level that the hold-down is on. The shrinkage length is entered in Structure input view from default assumptions given in the Hold-down settings. .
Moisture content input
The fabrication and in-service moisture content are input in the Design Settings. If deflection analysis is not activated you can input only whether it was greater or less than 19% (fabrication) or 15% (in-service), for use in nail withdrawal design. For deflection analysis the actual moisture content is input.
In- service Greater than Fabrication
If for some reason in service moisture content is greater than fabrication, shrinkage is set to zero.