Allowance for variability of materials

Provision is made in Variability Factors for the testing of more than one sample of a test specimen to allow for variability of materials. If many tests are carried out, each sample is required to satisfy the performance criteria. Where various tests are conducted on pierce-fixed roofs at different span lengths, using the same profile, type, and thickness of cladding, fastening type and pattern, and they have the same mode of failure, they must be included as complying with the number of units in Variability Factors.

Where only static testing is conducted and cyclic test verification testing is not used, the variability factors must be strictly in accordance with Variability Factors.

The design capacity (R _d ) must satisfy

R _d < R _min / k _t where R _min is the minimum test value and the factor k _t is given in Variability Factors.