The AISC LRFD 3rd edition lists threshold stress ranges, Fth, below which no evaluation of fatigue resistance is required...implying infinite life at those stress ranges.
The AASHTO LRFD 2003 lists exactly the same threshold ranges, but the commentary states that infinite life is achieved only when the design stress range is less than one-half of the thresholds (commentary 6.6.1.2.5).
One possible reason for this difference is that bridges are more likely than buildings to be subject to corrosion (which can reduce the endurance limit).
But does anyone know for certain why there's this difference? (Or who to call to find out...)
TIA!!
The AASHTO LRFD 2003 lists exactly the same threshold ranges, but the commentary states that infinite life is achieved only when the design stress range is less than one-half of the thresholds (commentary 6.6.1.2.5).
One possible reason for this difference is that bridges are more likely than buildings to be subject to corrosion (which can reduce the endurance limit).
But does anyone know for certain why there's this difference? (Or who to call to find out...)
TIA!!