Evaluating the potential of a rolling deflection measurement system to estimate track modulus

Over the past two decades, a rolling deflection measurement system aiming to continuously measure the track modulus has been under development at the University of Nebraska – Lincoln under the sponsorship of the Federal Railroad Administration. This system measures the relative vertical distance (referred to as Y rel ) between the rail surface and the rail/wheel contact plane at a distance of 1.22 m from the nearest wheel to the sensor system. The aim of this study was to investigate the potential of using the Y rel measurement as an indicator of the track modulus for various rail foundation conditions. To meet this objective, a detailed finite element model capable of simulating moving loads and track modulus variation was developed. One of the unique contributions of this study is that it presents a comprehensive study of the Y rel –track modulus relationship by defining more realistic support conditions using discrete spring supports and by simulating the stochastic nature of the track modulus along a 160-m track length. The numerical model was employed to examine the accuracy of estimating the track modulus using the Y rel measurements when foundation stiffness is variable. Furthermore, the correlation between the statistical properties of the track modulus and Y rel was studied over different track segment lengths.