How do I obtain collector forces within a floor diaphragm?
Answer: The collector forces within a floor diaphragm may be measured through the following process:
1. Define a semi-rigid diaphragm, then apply diaphragm forces, as shown in Figure 1:
Figure 1 - Apply diaphragm forces
2. For a given load case, display any stress or shell force, as shown in Figure 2:
Figure 2 - Display stress or shell force
3. Where maximum chord forces are expected, draw or define a section cut, as shown in Figure 3:
Figure 3 - Maximum chord forces
4. Moments about the Z-axis represent in-plane moments. Ensure that the resultant-force angle is zero, then select Refresh, as shown in Figure 4:
Figure 4 - In-plane moment
5. 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
6. 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
7. Again, ensure that the resultant-force angle is zero, and refresh as necessary. Given this example model, the shear/collector force, which is presented in F2, is 2559 lbs., as shown in Figure 7:
Figure 7 - Shear and collector forces