Thermal Loads on Rails

[c_villacorta]

Question on thermal loading for metal railings:
I am working on designing a metal rail with requirement for thermal expansion/loading, project specs states:
"Provide handrails and railings that allow for thermal movements resulting from the following maximum change (range)in ambient and surface temperatures by preventing buckling, opening of joints, over-stressing of components, failure of connections, and other detrimental effects. Base engineering calculation on surface temperatures of materials due to both solar heat gain and nighttime-sky heat loss.
Temperature Change (Range): 120°F, ambient; 180°F, material surfaces."
-Or see attachment for the spec itself.

What's the correct interpretation of the given temp data? Should ΔT be 180°F or ΔT=180°F-120°F=60°F ?
I am using Staad.Pro for the analysis as well as manual calcs. The project is in NY if it helps. Thanks!

 

[SlideRuleEra]

ΔT=180^o.

Air (ambient) temperature range is 120^o.
Temperature range for the metal is 180^o. The difference in the two ranges is caused by metal's extra heat gain from solar during the day and radiant heat loss to the night sky.

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