FRT 210, Strain Gaging Hold-Down Bearing Links on the I-65 Kennedy Bridge

The cantilever truss end spans are secured by uplift bearings. The bearings are attached to the knees of the trusses by twin links joined by connection plate. The links are pinned to the knees of the trusses and to the uplift bearings. A KTC inspection of the movement of the bearings/links/truss knees in June 2007 revealed excessive movement between the bearings/knees due, in part to wear in the pin holes in the links and possibly the uplift bearing and truss knee pin connections Researchers will acquire and set up a multi-channel strain gage signal conditioner/data acquisition system to take strain gage data concurrently from 2 links. Strain gages will be installed on the link pairs of the four uplift bearings to measure differences in strain between each link of the link pairs. Gages will be installed on both faces of the links to determine whether the resulting strains are equivalent The four gages at each hold-down bearing will be monitored under normal traffic. The data from each gage will be viewed concurrently in real-time and recorded. Testing at each site will be conducted over a 4-hour minimum period to ensure significant uplift forces are measured. The strain/time history data will be recorded. Strain/time traces of concurrent readings of the four gages at each uplift bearing will be provided in graphic/tabular form in a memorandum report. That data should enable the Cabinet to determine if the links are engaging concurrently and if the strains on both faces of a link are equivalent (to detect possible bending in the links).