§29.613 Material strength properties and design values

(a) Material strength properties m ust be based on enough tests of m aterial meeting specifications to establish design values on a statistical basis. (b) Design values m ust be chosen to minimise the probability of structural failure due to m aterial variability. Except as provided in subparagraphs (d) and (e), com pliance with this paragraph m ust be shown by selecting design values that assure m aterial strength with the following probability: (1) Where applied loads are eventually distributed through a single member within an assembly, the failure of which would result in loss of structural integrity of the component, 99% probability with 95% confidence; and (2) For redundant structures, those in which the failure of individual elem ents would result in applied loads being safely distributed to other load-carry ing m embers, 90% probability with 95% confidence. (c) The strength, detail design, and fabrication of the structure m ust m inimise the probability of disastrous fatigue failure, particularly at points of stress concentration. (d) Material specifications m ust be those contained in documents accepted by the Agency. (e) Other design values m ay be used if a selection of the material is made in which a specimen of each individual item is tested before use and it is determined that the actual strength properties of that particular item will equal or exceed those used in design.