Live Load Testing and Load Rating of Older Glulam Girder Bridges.

摘要

This paper is focused on the field performance of glulam girder bridges built prior to 1970 in the Pacific-Northwest Region of the United States. Although many of these bridges are still performing satisfactorily and recent inspections have not detected any significant structural problems, new reductions in the load rating process are significant. The reductions associated with these pre-1970 glulam bridges are based on the beams not having the higher-quality tension laminations found in modern glulam beams. Due to the absence of these specially-graded tension laminations , research studies suggest that these glulam beams have lower strength values and require engineers to reduce their bending resistance values by up to 25 percent. The aim of this field investigation was to develop a modified approach to load rating pre-1970 glulam bridges that results in less severe reductions than required in the current load rating procedure. This poster reports on the recent field testing conducted at several bridges in State of Oregon during August, 2009. Field testing involved physical mapping, non-destructive testing, and core sampling of girder laminations in those zones loaded in tension. In addition, girder deflection and strain measurements were recorded under static live loading.