In 2009-2010, the Transportation Technology Center, Inc. measured gage restraint of mainline concrete tie track affected by missing or broken fasteners. Measurements were taken at the Facility of Accelerated Service Testing and at the western mega site in revenue service.
A concrete tie rail fastener provides gage restraint through the toe load (hold-down force) on the base of the rail provided by the tie clips and through lateral resistance from the insulators pressing against the base of the rail. Missing or broken fasteners can reduce the track’s gage strength. the research showed the following:
- Missing or broken field side clips were found to have less effect on gage restraint than missing or broken gage side clips. Missing field side insulators had a greater effect on gage restraint than missing gage side insulators. Gage side clips appeared to play a bigger role than field side clips in preventing gage widening due to rail roll. On the other hand, field side insulators had a bigger role than gage side insulators in resisting gage widening due to rail translation.
- It took eight consecutive tie missing only clips or insulators to reduce gage restraint below the maximum limit. When both clips and insulators were missing, however, it took only three consecutive ties to reduce gage restraint below the maximum limit.
Measurements were taken in warm and cold temperatures for both tangent and 2-degree curve track locations. Measurements were taken primarily using a light track loading fixture and were verified using the Track Loading Vehicle.
The research presented in this Technology Digest addresses one of the concerns for the performance of concrete ties under heavy axle load train operations, including missing or broken fasteners, rail seat abrasion, pad wear, loss of toe load, improper fastener configuration, and excessive lateral rail movement. A similar study was done for wood ties in 1994. The research is funded jointly by the Association of American Railroads and the Federal Railroad Administration under the revenue service mega site testing program.