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Define a semi-rigid diaphragm, then apply diaphragm forces, as shown in Figure 1:
Figure 1 - Apply diaphragm forces
For a given load case, display any stress or shell force, as shown in Figure 2:
Figure 2 - Display stress or shell force
Where maximum chord forces are expected, draw or define a section cut, as shown in Figure 3:
Figure 3 - Maximum chord forces
Moments about the Z-axis represent in-plane moments. Ensure that the resultant-force angle is 90 in order to enforce vertical line, then select Refresh, as shown in Figure 4:
Figure 4 - In-plane moment
Compression and tension chord forces are then given as the value of each Z-axis moment divided by slab width, as shown in Figure 5:
Figure 5 - Compression and tension chord forces
For shear and collector forces located at the connection between the diaphragm and a shear wall, draw or define a section cut next to the support which follows the wall direction, as shown in Figure 6:
Figure 6 - Shear and collector forces
Again, ensure that the resultant-force angle is 90, and refresh as necessary. Given this example model, the shear/collector force, which is presented in F1, is 2952 lbs., as shown in Figure 7:
Figure 7 - Shear and collector forces
- Local axis of section cut 1, 2 and Z are similar to a frame element, resultant force angle indicates angle between X global axis and section cut local 1 axis
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