Technology Digests / Laboratory Testing and Evaluation of Joint Bar Clamps

TD26-022

Date Posted: October 6, 2026
Authors
  • Ananyo Banerjee
  • Sirius Roybal
  • Denise Valdez
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Key Findings

  • Both styles of joint bar clamps successfully completed at least 25 million gross tons (MGT) of laboratory rolling load testing with 50,000-pound wheel loads. All observed failures prior to 100 MGT occurred due to the joint bars rather than the clamps. This performance provides evidence that joint bar clamps can survive in a heavy axle load environment for temporary repairs.
  • Laboratory testing shows the ability of clamped joint bars to resist longitudinal rail movement and is limited to an approximate range between 12,000 and 50,000 pounds, depending on clamp style, quantity, and configuration.
  • Clamp movement was minimal; sliding between the joint bar and rail occurred during both rolling load and longitudinal resistance tests. Rail and joint bar surface conditions were not altered for these tests.
  • Proper joint bar installation and clamp-bolt torque are critical to joint performance. A defined bolt-torque schedule is essential for long-term performance. Joint bars without bolt holes should be used with clamps to reduce the possibility of bolt hole cracks.

Laboratory Testing and Evaluation of Joint Bar Clamps

Since 2024, MxV Rail has been evaluating joint bar clamps regarding their effectiveness in holding joint bars on 136 lb/yd. rails without the need for bolts to keep the joints in place. Two different vendors supplied the joint bar clamps traditionally used in rail networks in Europe but not in the North American freight rail network per current regulations.1 Rolling load testing along with longitudinal resistance tests were conducted at MxV Rail, and the results from those tests are provided in this Technology Digest. BACKGROUND The North American freight rail network has one of the highest axle load usages in the world with typical axle loads above 35 tons. Continuous welded rail (CWR) is most common on tracks belonging to Class 2 and higher track classifications. Weld or rail breaks are often repaired with bolted plugs until they can be welded. This repair method typically requires drilling holes for bolts,…