Technical Reports

Attentuation of Dynamic Response of Special Track Work Foundations Subjected to Impact Loading

  • 01
  • May
  • 2003
AUTHOR: Satya P. Singh, David D. Davis, Don Guillen, David Williams
SUBJECT: Tracks & Structures
KEYWORDS: High Impact Loads, Damping, Wood Tie Ballasted Track, Concrete Tie Ballasted Track
ABSTRACT: This report deals with damage to special track work due to high impact loads and the beneficial effect of increasing damping in these foundations. Additional damping attenuates the high magnitude and high frequency of impact generated transient vehicle- track vibrations. This report covers the first phase of means, manners, and options for analyzing and enhancing the damping at the special track work locations, especially the crossing diamond foundations. A conventional wood-tie ballasted track at TTC’s Facility for Accelerated Service Testing had a damping value of about 56 lbs/in/sec/tie/rail. A conventional concrete-tie ballasted track on the Railroad Test Track (RTT), on the other hand, had a damping value of about 164 lbs/in/sec/tie/rail. The measured values were very low compared to the value of the optimal damping of about 300 lbs/in/sec/tie/rail determined in a previous study conducted by TTCI. Since the traditional crossing diamond foundation is very similar to a conventional open track foundation, the damping in existing crossing diamond foundations cannot be expected to be more than the ballasted track on the RTT; i.e., 164 lbs/in/sec/tie/rail. The damping of crossing diamond foundations therefore needs to be increased. The measured damping values at other modified track beds on the RTT consisting of rolled ballast mat and undertie pads were found to be respectively 319 and 237 lbs/in/sec/tie/rail, and appear to meet the optimal damping provision criterion. Similar modifications then could be used to increase damping in crossing diamond foundations. This work was conducted under Task Order 139 of the FRA’s Research and Development Plan. During Phase 2, and in concert with a companion AAR program, results of laboratory tests on various damping pads will be analyzed to produce rank-attenuation relationships. Pads will be tested in heavy axle load environment to determine the deterioration of the dynamic performance and to gage their durability.