Full Paper_A NOVEL ALGORITHM FOR IDENTIFYING BALLAST DYNAMIC PROPERTIES FROM IMPACT TESTING METHOD

In the past few years, the railway industry has been facing an unprecedented demand for the expansion of the railway network leading to the widespread use of ballasted tracks. Ballasted tracks are easy and quick to construct, making them a cost-effective solution for the railway industry. Ballast dynamic properties play a crucial role in the analyses for the performance and safety of the railway system, so accurate identification is necessary. Previous studies have taken a simplified approach by treating the sleeper-ballast system as a single-degree-of-freedom (SDOF) for ease of analysis. However, this overlooks the impact of sleeper stiffness and damping on the system’s dynamic behavior. To account for this, a multi-degrees-of-freedom (MDOF) model can be used. The sleeper-ballast numerical model will be based on a beam resting on an elastic foundation, where the sleeper is modelled as a finite element beam and the ballast layer is represented as a spring-damper foundation. Traditional methods for testing of ballast dynamic properties are time-consuming and destructive, which can result in significant disruption to the railway network, therefore a non-destructive testing method that accurately characterizes the ballast dynamic properties is necessary. An instrumented impact hammering method, a non-destructive-testing approach, will be chosen. The impact force obtained from the testing will be used as an input parameter for the identification algorithm, the simulated and measured acceleration response will be curve-fitted by adjusting the ballast dynamic properties in the numerical model until the sum-square-residual of the two data sets reaches the acceptable range. This insight will provide a more accurate identification algorithm that can be further used for ballast dynamic properties.

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