Measured deflections of a four girder bridge under varying bracing conditions

This thesis reports a study comparing measured vertical girder deflections, twisting of bottom flange, impact factors on girders, and lateral load distribution from two different bracing conditions under a controlled load and normal traffic loads on the Holston River Bridge located in Knoxville, TN. The two controlled load tests performed were a crawl (static) and speed (dynamic) tests. In the first bracing condition the bridge girders were laterally braced. In the second condition the bridge had some lateral bracing removed. This thesis describes in detail how data were obtained for the comparisons of results between the two bracing conditions. Measurements of the girder deflections were achieved by using small apparatuses that resemble cantilever beams.

The static test results show that when lateral bracing was removed, the changes in girder deflections were not significant; however, the dynamic test results showed a significant change. The lateral load distribution was essentially unchanged by the removal of bracing. The static test results also showed that the bottom flange angle of twist on an unbraced girder increased significantly after removal of the lateral bracing.