Instrumentation of the Twelvemile Bridge
An experimental precast, post-tensioned concrete segmental girder bridge over Twelvemile Creek in Campbell County was instrumented with stress and strain sensors. Those sensors were read during beam fabrication and the initial portion of construction. The work was performed to address Transportation Cabinet questions about structural performance and also to assess the effect of long-term creep. The study and bridge were not completed as originally designed due a beam failure during
... during post-tensioning. A variety of stress, strain, and deflection measuring techniques were to be employed during the study. Several of those including concrete stress and strain meters, and vibrating-wire strain gages were embedded in beams and one pier cap. Those sensors were read during several phases of fabrication and construction. Concrete maturity meters were also employed to determine temperature-time relationships with increases in curing strength for concrete used in the pier caps and in one beam. Compressive strength and modulus tests were also performed on test cylinders obtained from the pier and beam concrete. This report describes the progress of the field instrumentation and laboratory work to the termination of the study. The study was terminated due to the failure of a beam during erection. The bridge was completed using conventional steel girders. Based upon the limited study findings and the beam failure, recommendations are provided that the Transportation Cabinet: 1) conduct further research related to the use of maturity meters, and 2) consider employing nondestructive testing of similar beams in fabrication shops.