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Shearwalls checks the compressive resistance of the wall bottom plate beneath the shear wall end chord stud pack.
Compressive Resistance
The factored compressive resistance perpendicular to the grain to the
Qr = A Fcp, where,
Fcp = f KD KScp KZcp KB fcp, where
f = 0.8
Fcp is the specified compressive resistance perpendicular to the grain of the wall framing material grade
KD is the load duration factor = 1.15 for wind and seismic
KScp is the wet service factor from O86 Table 6-10 = 0.67 for in-service moisture greater than 15%
KZcp is the size factor from 6.5.6.4 which we can assume will be 1.15 for all bottom plates
KB is the bearing factor from O86 6.5.6.5
All factors except KB are given in the notes to the Framing Materials table.
Cross-sectional Area A
A is the cross-sectional area of the end studs, the same A as is used in the bending term of the deflection equation, so it can be found in the Deflection table in the Design Results output. .
Bearing Area Factor
The bearing area factor KB is defined as
KB = (lb + 0.375) / lb
where lb is the width of the stud pack. Cb is 1.0 for lb ≥ 6.0", so stud packs with 4 members or more are unfactored.
KB applies only to those force locations that are under openings, and the openings do not extend to the bottom of the wall.
The notes to the framing material table indicate the possibility of the of the Cb factor but to not provide the value, as it can be different for each compression force location in the structure.
Design Results Output
Refer to Design Results Output for a description of the output tables showing compression force design.
Non-wood or Proprietary Walls
There are no assumptions made as to the composition of end chords for Non-wood/Proprietary walls and no compression force design for these walls.