Determination of Railway Vertical Wheel Impact Magnitudes: Field Trials

The authors utilized both experimental and finite element modeling methods earlier to develop both a classical inverse approach as well as a root mean square (RMS) method to estimate the magnitude of wheel impact forces on railway track-like structures. This study presents some results from the field trials of the techniques developed in (Lee, M.L., Chiu, W.K. and Koss, L.L (2005). A numerical study into the reconstruction of impact forces on railway track-like structures. Structural Health Monitoring: An International Journal, 4(1), 19–45. Lee, M.L. and Chiu, W.K (2005). The reconstruction of dynamic impact forces on a railway track-like structure by using an inverse analysis technique. In: Proceedings of the 4th Australasian Congress of Applied Mechanics, pp. 605–610, Melbourne, Australia. Lee, M.L. and Chiu, W.K. (2005). A comparative study on impact force prediction on a railway track-like structure. Structural Health Monitoring: An International Journal, 4(4), 355–376.). A length of track carrying freight rail traffic and situated along the Melbourne–Geelong line (Victoria, Australia) is instrumented with accelerometers and shear-bridges. The instrumentation consists of five rail cribs instrumented with a shear-bridge and an accelerometer on the rail foot at the midspan of each crib. Using the shear-bridge instrumentation as a check, it is found that the proposed inverse analysis method (IAM) shows potential in not only reconstructing clean impact strikes but also in reconstructing strikes occurring outside of the shear-bridge effective zone within a single crib. Furthermore, based on the principle of superposition governing linear systems, multiple impact strikes within a single crib of rail are also able to be reconstructed. Regarding the RMS method, it is found that while a good correlation (R ≈ 0.8) existed between wheel impact force and track response RMS, a significant spread existed in the data.