Thermal Expansion
Thermal Expansion
(OP)
With regards to the change in temperature parameter, I believe that the upper value is the maximum temperature that the steel will experience in operation/field. What does the lower value represent? I would assume that this is the temperature of the steel during cutting of the steel to the length specified on the design drawings. Is there some rule of thumb value for this lower temperature?






RE: Thermal Expansion
Things remain to be clarified, like the transition from the specified temperatures along the faces of the building towards the soil, that for rigid setups near the base may turn very high stresses if kept constant.
Bridge code is more specific as usual on gradient temperature issues, but the idea is always the same, to identify the ranges to explore in analysis and proper placement of the temperature excursions in the models.
RE: Thermal Expansion
I would say the minimum temp would be the air temp in the middle of winter of the plant was shut down. Unless you know for certain which time of year the steelwork is to be installed.
RE: Thermal Expansion
Also consider, Concrete shrinks over time. If you have a supported concrete deck, this will probably be the controlling factor.
The steel is "locked in" when the bolts are tightened and field welds completed.
RE: Thermal Expansion
For example, one of AASHTO's methods provides min/max values for steel of 0 and 120 deg. F but if you evaluate delta T for 120 you are essentially determining the horizontal loads applied due to expansion or contraction of the steel after the steel is "locked in"