Calculate the Differential Loads:

Calculate the Differential Load (incremental uplift force). The differential load is the difference between the uplift load at each level vs. the level above. This load transfer point is where the uplift load is transferred into the structure. This may happen on every level or may skip levels.

(Note: if a load transfer point is used on every level, fewer trimmers will be used and plate sizes can be smaller. However, more take-up devices and plates will be needed. If floors are skipped then fewer take-up devices are required but rod size and trimmers may be increased.)

Sample: Run 3A uses R6 rod (3/4”) on level 1 and R5 rod (5/8”) on levels 2 and 3. Take-Up devices are always installed at levels where the threaded rod size changes.

1. In sample Run 3A, the differential load transfer will occur at level 1 and level 3.

2. The differential load at level 1 is the difference between level 1and 2. (8,000-5,500 = 2,500 lbs.)

3. The differential load at level 3 is the remaining run load. (8,000 – 2,500 = 5,500 lbs.)

Note: Load transfer points are always on the floor of the story above. Loads are carried through the floor and into the story below. (Exception: when a header is used with short trimmers in a wall, usually at the top floor)

After the differential load information is put into the table the balance of the runs can be determined.

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