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Performance of Stress-Laminated Timber Highway Bridges In Cold Climates

机译：寒冷气候下应力层压木公路桥梁的性能

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摘要

This paper summarizes recent laboratory and field data studies on thermal performance of stress-laminated timber highway bridges. Concerns about the reliability of stress-laminated deck bridges when exposed to sub-freezing temperatures triggered several investigations. Two laboratory studies were conducted to study the effects of wood species, preservative, moisture content, and temperature variations on pre-stressing bar forces (critical factor) in stress-laminated decks. The field performance of several stress-laminated timber bridges were monitored within a Nationwide Timber Bridge Monitoring Program, a cooperative effort by the U.S. Forest Service, Forest Products Laboratory and Federal Highway Administration. Bar-force and temperature data from a subset of bridges were continuously monitored for a period of 2 to 5 years with remote data acquisition systems. Significant pre-stressing bar-force losses were observed in laboratory studies when the moisture content of deck laminations were at 30 percent and greater and the deck temperature reached 0℉ (-18℃) and below. The field study concluded that the magnitude of cold-temperature induced bar-force losses were not significant enough to warrant special considerations in the U.S. bridge design code. However, it may warrant special considerations in cold weather regions outside the United States whenever deck lamination moisture contents exceeding 20 percent are combined with ambient temperatures remaining below 0℉ (-18℃) for extended periods of time.
机译：本文总结了有关应力层压木材公路桥梁热性能的最新实验室和现场数据研究。对应力叠层桥面桥梁在承受亚冰点温度时的可靠性的担忧引发了几项研究。进行了两项实验室研究，以研究木材种类，防腐剂，水分含量和温度变化对层压板中预应力杆力（临界因子）的影响。在美国全国林业局，林产品实验室和联邦公路管理局的共同努力下，在全国范围的木桥监测计划中对几处应力层压木桥的现场性能进行了监测。使用远程数据采集系统连续监测来自桥梁的一部分的力和温度数据，持续2到5年。在实验室研究中，当甲板叠片的水分含量为30％或更高且甲板温度达到0℉（-18℃）或更低时，观察到了显着的预应力钢筋损失。现场研究得出的结论是，低温引起的钢筋损失的幅度不足以保证美国桥梁设计规范中的特殊考虑。但是，当甲板覆膜的水分含量超过20％并长时间保持低于0℉（-18℃）的环境温度时，在美国以外的寒冷地区可能需要特别考虑。

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