Comparative study on impact force prediction on a railway track-like structure

The ability to estimate an impact force being imparted onto a structure is highly valuable to its overall health monitoring scheme. This study compares impact force prediction on a railway track-like structure by a number of methods. One proposed technique utilized to estimate dynamic impacts on railway tracks involve correlating a root mean square (RMS) calculation of the track response over a selected frequency bandwidth with different impact force levels. Another technique involves the use of strain gauges configured into a full bridge circuit to reconstruct the time history of the impact force on the track structure. A third method utilizes a classical inverse analysis approach to reconstruct the force time history with a calibrated transfer function in the frequency domain. This article uses both finite element and experimental techniques to evaluate the aforementioned methods with regard to input impacts with constant magnitude and varying durations. It is seen that the RMS method is not effective in predicting impact forces with like magnitudes but varying durations. This is because the RMS relies on measuring energy in the response spectra, which varies according to input impact energy. It was also shown that measuring strain is an effective method of reconstructing an impact force waveform; however its efficacy is reduced when the impact event becomes highly dynamic. This is because strain relies on structural deformation, which is dependent on the loading time history. It is seen that an inverse analysis technique, which relies on the calibration of a frequency response function to facilitate the reconstruction of impact forces is relatively immune to varying impact durations. This is due to the structure's relative linearity over the lower frequency region, which is a critical consideration when choosing the inverse analysis method.