Originally posted by John Breen:
Wind loadings on exposed piping that is not housed within a building are normal (creditable), and these loadings should be included in the design basis and considered in the sustained load case. Furthermore, I think that if Ben's L5 case includes the 25 year wind it should be combined with the sustained loadings of pressure and weight as a normal sustained load combination that should be compared to 1.0 X Sh. However if it includes the 100 year wind, then it should be considered an occasional load combination and the stress for comparison should be 1.33 X Sh.
This has not been my experience. A wind load is pretty much always treated as occasional (OCC in Caesar). We've talked to structural engineers about wind loading, since ASCE 7-95 (now 7-98) is the basis for the wind pressures we use. B31.3 considered the multiplier for increased allowables based on duration and frequency. I've sought input from structural engineers if there is any time element involved in the increase in allowables they use for structural steel under wind loading.
The answer basically is no. Wind is considered a temporary loading, much like a hydrotest, and allows for the use of increased stress values, essentially reducing the factor of safety, to allow these situations to be considered without unnecessarily increasing the cost of the design.
In looking at the ASCE criteria, the terminology (which I don't have in front of me, I'm going on memory) suggests the calculated wind speeds are of a transient nature.
As such, I would have a hard time including a wind load in a stress review that did not consider the increased allowables for a temporary loading. To include wind in a simple sustained case review seems excessively conservative.
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