Final answer:
Importance factor 1.0 corresponds to mean recurrence intervals of 50 to 100 years.
Step-by-step explanation:
The importance factor, denoted by "I," is a crucial parameter in structural engineering that reflects the significance of a structure or component within a given context. In this context, an importance factor of 1.0 indicates a standard or baseline level of importance. The mean recurrence interval (MRI) is the average time between occurrences of a specific event, such as a design load or hazard.
To calculate the MRI corresponding to an importance factor of 1.0, we can use the formula: MRI = T / (I * R), where T is the return period, I is the importance factor, and R is the reliability index. For an importance factor of 1.0, the MRI simplifies to T / R. Given that T = 50 years for the lower limit and T = 100 years for the upper limit, the corresponding MRIs are 50 years and 100 years, respectively.
Therefore, an importance factor of 1.0 corresponds to mean recurrence intervals of 50 to 100 years. This implies that the structure or component under consideration is designed to withstand events with return periods ranging from 50 to 100 years, ensuring a reasonable level of safety and reliability within that timeframe.