TM 5-852-9/AFR 88-19, Vol. IX
CHAPTER 3
STRUCTURAL
3-1. General. This chapter extends the basic structural design criteria to cover items that are unique to arctic
and subarctic regions. It extends the criteria provided in TM 5-852-1/AFR 88-19, Volume 1, and other
criteria documents.
3-2. Structural design. Structural design of building construction in arctic and subarctic regions is unique
only in that conditions found elsewhere are compounded there. Large, and often indeterminate design loads,
wide seasonal temperature variances, short construction seasons, and limited availability of skilled labor,
construction materials, and transportation form the basis of design problems. Department of the Navy,
NAVFAC DM 9, and Department of the Army, TM 5-349, discuss these problems.
3-3. Special considerations.
a. Design loads. Design loads for selected arctic locations are listed in TM 5-809-1/AFM 88-3, chapter
1, and TM 5-80910/NAVFAC P-355/AFM 88-3, chapter 13, and American National Standards Institute
(ANSI) A58.1. Climatological data at remote sites should be obtained from individual sites to determine snow
and wind loads. Precipitation varies greatly between sites in the same general area and between areas;
consequently, snow depths and densities also vary. Many military installations have building sites at two or
more greatly differing elevations, and usually have different snow and wind loads at each location. Roof
systems with vertical irregularities are subject to increased snow loadings due to drifts and, in certain roof
configurations, snow can slide from high roofs to low roofs. Additional loads due to snow drifting, plus
additional loads and impact forces associated with sliding snow, must be considered during structural design
of roof systems.
(1) Wind loads and related problems. Metals that extend through building walls from the exterior
to interior will contract in the extreme outside cold and expand in the interior heat. If metals are restrained
at the wall, this expansion/contraction can result in unusual stress on the buildings. Solar radiation on metal
surfaces of one side of a structure, with extreme cold in shadows on the opposite side, has caused buildings
to rack or be distorted. These conditions can be minimized or avoided by painting, by providing for expansion
and contraction in connections, and by avoiding designs which require continuous metal connections through
insulated walls. When used as exterior walls, metal-surfaced sandwich panels with insulation as a fill material
can cause problems. When the outer skin is exposed to extreme cold, it will contract, while the inner skin,
exposed to room temperature, maintains a constant size. As a result, the panels deflect inward, which could
result in outer skin failure, excessive shearing stresses in the insulation, or excessive tensile stresses in the
inner skin. Providing adequate skin plate thickness or internal ribs will reduce the deflection.
(2) Ice loads. Solar radiation and heat transferal from within the building melts snow on the roof.
As the roof cools with a drop in air temperature or with darkness, this water turns to ice. Repetition of this
process results in glaciation. Glaciation occurring on a building eave is frequently referred to as an "ice dam"
(see figure 3-1). This concentrated type of loading must be accounted for in the design.
b. Material considerations. Common structural materials can be used in arctic and subarctic regions with
few problems. Some special considerations must be remembered, however.
(1) Wood. Low humidity conditions are common in buildings where subfreezing temperatures reduce
the amount of moisture in the air which can be taken into heating Systems from outside. Frequently, other
considerations prevent the addition of moisture as the air is heated. The resultant dry atmosphere draws
moisture out of the wood. As a result, wood shrinks, adhesives dry, planks and timbers check and split,
fasteners loosen, and warping occurs. The use of kiln-dried lumber or laminated beams will prevent some of
these problems.
(2) Steel. At cold temperatures, steel will change from a ductile to a brittle material. This change
takes place at a point called the transition temperature, which can vary over 100EF due to differences in
composition and grain size. Increases in carbon and phosphorus content will raise the transition temperature.
Adding nickel will lower the transition temperature, as will decreasing the grain size by heat treatment. When
designing structures subject to impact loadings, consideration should be given to specifying steel that has
impact resistance at low temperatures. Building foundation pilings have broken while being driven and
3-1
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