Field Instrumentation of Indiana southern Railroad, Spencer Subdivision, Bridge 17.44 over White Lick Creek
Researchers at the S-BRITE Center worked with the Indiana Southern Railroad to explore live load stress conditions generated by train traffic over Bridge 17.44 in Central Indiana.
On Tuesday, December 2, 2014, field testing was conducted on Indiana Southern Railroad, Spencer Subdivision, Bridge 17.44 over White Lick Creek near Mooresville, Indiana by researchers at Purdue University’s Steel Bridge Research, Inspection, Training, & Engineering (SBRITE) Center. The SBRITE team was commissioned by the Indiana Southern Railroad, LLC, to perform the work. Live load stress ranges were measured at key locations on the main span in an effort to better understand the live load stress conditions generated by train traffic over the bridge. A single day of testing was conducted using a test train of known dimensions and weight. Additionally, data were collected as random trains crossed the bridge over the course of the ensuing month. The controlled load testing provided a baseline response for the structure from which engineers responsible for the bridge can use to refine their analyses. The data from random train crossings provided a window into the live load stresses put upon the bridge during typical service loading, enabling a comparison with the test train used for controlled load testing.
Live load stresses generated by the random train traffic were consistent with that produced by the test train. Thus, the test train data provided a rational baseline that can be used for future analysis on the bridge, assuming service loading does not change. Additionally, findings from the load tests showed that the truss distributed live loads relatively even within the instrumented truss, especially considering the deteriorate state of the 125year old bridge. Furthermore, some minor bending stresses in the eyebars were observed, likely due to pin rotation constraint and straightening of eyebars during loading. However, the bending stresses were not significant and the majority of live load stress in the eyebars and loop rods was axial. Also, static, crawl, and high speed testing showed that the bridge did not experience dynamic stress amplification when the trains traveled at higher speeds. Finally, random train traffic monitoring revealed an effective stress range that puts the fatigue category E eyebar into a finite fatigue life regime.