Research on the Influence of Loading Frequency on the Dynamic Response of Concrete Sleepers

Abstract

The load generated during train operation is transmitted to sleepers through rails, and then from sleepers to trackbeds. As one of the important components of the track structure, sleepers are very important to the service-life and safety of railways. The running speed of the train will produce different load frequencies on the rails. To explore the response of sleepers under cyclical train loads, this research used the discrete element method to simulate rails and sleepers, and realizes the loading of sleepers by applying cyclic loads to the rails. The discrete element method was used to simulate the compression-failure test of the concrete sample to verify the reliability of parameters of the discrete element model. On this basis, the sleeper was simulated by the discrete element, and the change law of the mechanical parameters such as particle displacement, contact force, and stress of the sleeper under different loading frequencies were analyzed. The research results show that the sleeper particles under the rail had a large vertical displacement, and the maximum displacement and the maximum contact force of the particles in the sleeper increased with increasing loading frequency. The stress change trend of the sleeper under the left and right rails was the same, and both showed periodic changes with cyclic loading. The loading frequency had little effect on the stress of the sleeper. The vertical displacement, velocity, and acceleration amplitude of the rail all increased with increasing cyclic loading frequency, thereby increasing the force between the rail and the sleeper, and increasing the dynamic response of the sleeper.

Complex Modulus characterization of an Optimized Binder with SCMs: proposition of an enhanced Cement formulation to improve Stiffness Behavior and Durability of Mortars and Concretes

“…Furthermore, it was mostly observed an uptrend tendency in the low frequencies range for both viscoelastic parameters, which is in agreement with previous studies that have found an increase in the stiffness of concrete as the frequency decreases (Chen et al, 2022;Medeiros et al, 2015). However, there were divergent values, it should be noted that there was an exception for M2 AVCM, with a downtrend in low-frequencies and some values at 25 Hz, which could potentially be attributed to dynamic effects, labeled as outliers in Fig.…”

“…The behavior of increasing complex modulus with frequency up to 5-10 Hz, followed by a plateau, is resported as usual for viscoelastic materials, usually explained by the microstructure alignment, where further changes in frequency do not affect the modulus signi cantly, which literature can provide insight in similar aspects (Chen et al, 2022;Medeiros et al, 2015;Sanahuja et al, 2007). This is typically attributed to the increased stiffness of the material as the microstructure becomes more ordered at higher frequencies.…”