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原文传递 EVALUATION OF RETROFIT PROCEDURES FOR NAIL-LAMINATED AND STRINGER BRIDGES.

题名：	EVALUATION OF RETROFIT PROCEDURES FOR NAIL-LAMINATED AND STRINGER BRIDGES.
作者：	Larson-TD; Seavey-RT
关键词：	Beams-; Bituminous-construction; Bridge-decks; Bridge-design; Bridges-; Costs-; Deflection-; Evaluation-; Grout-; Inspection-; Laminates-; Load-tests; Minnesota-; Nails-; Retrofitting-; Strength-of-materials; Stringers-; Timber-
摘要：	Many of the 1,400 timber bridges in Minnesota need to be improved to meet present day standards. When the desired service level can be attained by widening a bridge six feet or less, a retrofit can be done by placing a second, wider, transverse deck onto the existing deck and substructure. Bridge components must be carefully inspected prior to a retrofit project. Bridge #6641 in Sibley County was retrofitted. First the bituminous surface was removed. A longitudinal beam supported the extended deck. Grout was poured and leveled and then nail-laminated panels were laid transversely. A bituminous surface was laid over the full width of the new deck. The cost of the project was $51,632. (Replacing the bridge was estimated to take 2-3 years and cost $215,000). The county quantified the strength change and load distribution characteristics of the retrofitted bridge deck. Static and dynamic tests were performed both before and after the retrofit. The tests show that adding a second deck effectively decreased the static deflections and improved the transverse load distribution. Nail-laminated timber bridge #2642, also in Sibley County, was retrofitted in 1992 and was load tested again in 1995. All dynamic deflections were lower than those of the post-retrofit tests in 1992. This improvement can be explained in part by the drying of the moisture that was introduced into the bridge deck during grouting. Subsequent drying would add stability to the bridge deck. A retrofitted timber bridge is expected to last an additional 20-40 years.
总页数：	2002/07. pp36
报告类型：	科技报告