Allowance for Variation
Factors to Allow for Variability of Structural Units
| No of units tested | Coefficient of Variation (COV) | |||
|---|---|---|---|---|
| 5% | 10% | 15% | 20% | |
| 1 | 1.2 | 1.46 | 1.79 | 2.21 |
| 2 | 1.17 | 1.38 | 1.64 | 1.96 |
| 3 | 1.15 | 1.33 | 1.65 | 1.83 |
| 4 | 1.15 | 1.3 | 1.5 | 1.74 |
| 5 | 1.13 | 1.28 | 1.46 | 1.67 |
| 10 | 1.1 | 1.21 | 1.34 | 1.49 |
| 20 | 1.06 | 1.13 | 1.21 | 1.29 |
| 100 | 1.01 | 1.01 | 1.01 | 1.01 |
Coefficient of Variation (COV) is derived from Standard Dev / Av for a group of tests. The COV to be applied to a series of tests is the average overall spans measured during a test schedule conducted over a continuous period using identical material.
For serviceability loads, a coefficient of 5% may be assumed unless there is evidence that a higher figure is warranted. For strength loads, a coefficient of 10% may be assumed unless there is evidence that a higher figure is warranted. For clip-fastened products, the applied depreciation factor may not be less than 1.3.
The number of units tested relates to the number of valid results derived from a given fastener configuration and purlin spacing.
For values between those listed in the table, interpolation may be used.
- Log in to post comments