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Hold-down forces are the tension forces created by the overturning uplift and wind uplift, counteracted by dead load. The program also calculates compression forces at the other end of the shear wall segment, created by the combination of dead and overturning forces, counteracted by wind uplift.
Tension forces are are used to design hold-down connections and calculate hold-down displacement for deflection analysis. At the other end of the segment, the program checks the compressive resistance of the wall bottom plate under the end chord studs, and calculates the contribution to shear wall deflection from the crushing of the bottom plate.
Generally speaking, a hold-down device is required at each end of the wall to resist forces from either direction, and compression forces at both ends must also be resisted.
Exceptions to this arrangement occur when the dead load counteracting force is greater than the tensile overturning force, in which case no force appears at what is ordinarily the tension end and the hold-down devices is not designed.
Irregular arrangements of openings on upper levels can create situations where the tension force on one level combines with a compression force on the level below. It is even possible for compression forces to appear on the lower level where hold-down forces ordinarily would, and vice-versa.
Tension and compression forces from hold-downs at the end of adjacent shear segments on the same level are not combined.
Output
The program shows both tension forces and compression forces in Elevation view and in Plan View. In Elevation view, the program shows loads and forces in one direction, so typically a hold-down is shown on one end and a compression force on the opposite end. You can select the opposite force direction to see the hold-down and compression forces reversed.
Both the compression force and hold-down force at each location shown in the Hold-down Design table in the Design Results output.
Dead Load Factor
Dead loads used to counteract overturning hold-down forces are factored with the lower load combination factor used when dead load counteract other loads. For compression forces, dead loads are not considered to be counteracting and the regular (non-counteracting) load combination is used for them. Refer to Dead Load Component for more details.