What does the repetitive member factor denote in wood design?

The repetitive member factor, designated as "Cr," tells us how much strength is gained in a structure when multiple identical members are used repetitively in a system. In wood design, when structural members, such as beams or joists, are used repetitively in a similar loading scenario, the structural performance is improved due to the distribution of loads and the reduced risk of failure.

By applying the repetitive member factor, engineers can adjust the permissible stress or design values of these members to encourage their efficient use while ensuring safety and performance under load. This factor accounts for the presence of multiple members under similar conditions, allowing for optimized design decisions that promote material efficiency and structural integrity.

The other factors mentioned do not pertain specifically to the concept of repetitive members in wood design. For example, "Cf" typically relates to the adjustment for certain factors like size or duration of load, while "Cfu" may correspond to specific conditions affecting the design of structural wood. "Ci" is generally associated with other criteria in the design of wood, such as the effects of wet service conditions. In this context, "Cr" accurately reflects the concept concerning the benefits of utilizing repetitive members in wood structures, making it the correct answer.