huangyhg

structural steel design in sub-zero temperatures
i have to design a small 15,000 sq. ft. single storey freezer building. (25 ft. height steel building with metal roof deck and insulated wall panels).
the operating temperature inside will be -50 deg f (-45 celcius). assuming summer construction, the differential temperature will be in order of 120 deg f (65 deg c). the building is completely insulated (walls, floors and roof).
are there any design guidelines i need to follow? any words of wisdom? any good details i should consider from your past experiences?
i appreciate your help.
daria
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if you designed this using the bs5950 you would design it using a special grade of steel whose design is based upon brittle fracture. ref clause 2.44.
the stellar group in jacksonville, fl specialize in this type of construction. they may be able to provide some help
a few points to consider:
1. an operating temp. of 50 deg. f is not a freezer, but a cooler. there is a big differance. the floor slab of a cooler does not need to be insulated, but be sure to have a good vapor barrier.
2. all joints in the insulated panel system must be well sealed and stagger the joints between insulation layers. warm, moist exterior air that infiltrates into the cooler will cause condensation. i've actually seen it rain in a cooler that was not sealed tightly!
3. as noted, there are specialty firms that design and build coolers. usually the enclosing building is a conventional design with a cooler built within it.
the operating temperature is -50 deg f (not +50)! that's definitely below freezing. based on the size of the building, we have calculated a shrinkage of 1.5 inches.
daria,
sorry, my bifocals weren't bifocalling! (:{ you can also forget about the rain inside the unit, it will be too cold to even snow! <g>
frost heave of the subgrade can be a concern and so the thickness of the insulation under the slab should be looked at carefully.
thanks for the responses so far. you are correct jheidt2543 about insulating the floor.
below the slab on grade, we have 6" rigid insulation on a sand bed that is heat traced. the steel columns go through all this sub-grade onto the concrete piers below. but the column base plates have to sit on a +/- 8" thick wood block acting as an insulator to prevent condensation at the base of the columns.
daria,
in canada we have structures (operating plants) that are exposed to ambient temperature that you are looking at (-45 deg c) and we have no problems with the serviceability condition of the structure. one thing you have to keep in mind is that all your steel is exposed to the same temperature, threfore the shrinkage is small relative to each of the steel members (assuming that the steel
i would consider high-strength steel, astm a572 gr. 50 type, except for the foundation columns, which, because of the possibility of vehicle impact, should be low-temperature api5lx.
all bolts outside the building freezing envelope should be regular astm a325 or astm a490 high-strength bolts, and all bolts in the freezing envelope are astm a320 l7 low-temperature, high-strength bolts.
cheers
beaver12,
the building is actually being constructed in ontario, canada. the entire structure is a freezer building, so i cannot consider the "inside out" concept, otherwise all structural steel will be exposed.
we are thinking of designing the entire building out of heavy timber construction using parallam beams & columns (coefficient of thermal expansion is about 1/4 to 1/5 of steel).

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