Imaging tools for evaluation of gusset plate connections in steel truss bridges

After the collapse of the Interstate 35W Bridge in Minneapolis, Minnesota, in 2007, transportation agencies began evaluating and rating their inventories of gusset plate connections. Connection evaluations require accurate drawings that detail the plate, member, and fastener geometries. These structural details should also accurately reflect the as-built conditions. For some connections, as-built information may not be available, or the available drawings may not represent the actual field conditions. To fill this gap, a new methodology was developed that enables rapid and accurate collection of field measurements for connection plate geometry. The method uses close-range photogrammetry techniques to rectify images taken with consumer-grade cameras using flat-field and fish-eye lenses. The technique has been demonstrated on full-scale gusset plates in the laboratory and in the field. Dimensional measurements from the processed images provided results that are as good as or better than conventional field measurements and with tolerances below what most engineers require for calculation of gusset plate connection capacity. This technique provides a new tool for bridge engineers to quickly collect gusset plate geometry that can be used in connection evaluations and rating and can further enhance bridge-management tasks.