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InTrans / Aug 14, 2018

Cold temperature effects on stress-laminated timber bridges

Stress-laminated bridges perform well, if adequate bar
force is maintained to provide the interlaminar friction
and load transfer between adjacent deck laminations.
Stress-laminated decks utilize both wood and steel
components; therefore, different material thermal properties
may cause bar force to change as the temperature
fluctuates. In response to concerns about the performance
of stress-laminated bridges in extremely cold climates,
a cooperative research project with the University
of Minnesota; the USDA Forest Service, Forest
Products Laboratory; and the Federal Highway Administration
was initiated to evaluate system performance at
temperatures ranging from 21.1å¡C to -34.4å¡C. Stresslaminated
bridge deck sections, constructed of Red Pine
lumber and high strength steel stressing bars, were
placed in cold temperature settings of -12.2å¡C,
-17.8å¡C, -23.3å¡C, -28.9å¡C, and -34.4å¡C, while bar
force measurements were collected. Testing was completed
at three different moisture content levels: >30,
17, and 7 percent. At -34.4å¡C, bar force losses were
high when the deck moisture content was greater than
30 percent and were moderate to low when the moisture
content was less than 18 percent. In all cases, bar force
loss was fully recovered after temperatures increased to
21.1å¡C.

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