Structural load testing and flexure analysis of the Route 701 Bridge in Louisa County, Virginia.

A continuous slab bridge in Louisa County, Virginia, on Route 701 developed a planar horizontal crack along the length of all three spans. This project was designed to determine if the current load rating of the bridge could be raised and to document the behavior and stiffness of the bridge to serve as a benchmark for possible future tests, which may determine if there is progressive damage attributable to crack growth. These objectives were accomplished through field tests performed in November 2003. One truck (loaded to three different weights) was used to perform static and dynamic tests on the bridge, and the truck was oriented in three test lanes. Vertical displacement gages (deflectometers) attached to the underside of the bridge slab were used to measure deflections during the truck passes. The recorded deflections were analyzed and normalized to document the behavior of the bridge. The values were also compared to estimated design values in accordance with the AASHTO "Standard Specifications for Highway Bridges." Under the testing loads, the bridge behaved elastically, and thus raising the load rating of the bridge was considered safe. The deflections and process are presented to allow comparisons with future tests to determine if there is progressive damage to the bridge attributable to crack growth.