Charles Becht IV, Ph.D., P.E.; Greg Hollinger; Charles Becht V
Development of Basic Time-Dependent Allowable Stresses for Creep Regime in Section VIII, Division I / ASME STP-PT-024, 2008
The existing rules in the ASME Boiler and Pressure Vessel Code, Section VIII, Division I make no distinction as to the duration of load, although the allowable stresses in the creep regime depend upon time dependent creep properties for the material. Nominal 100,000 hour durations are used in determining the allowable stress. The report proposes two changes to the Code that would lead to more efficient design in the creep regime. 1) Higher allowable stresses for loads with a total duration not exceeding ten hours over the design life, such as earthquake and extreme wind. 2) A design approach that permits consideration of load duration in setting the allowable stress, using an approach that uses the existing allowable stress tables in the Code.