Flexural Behavior of Concrete Crossties under Different Support Conditions

Successful mapping of concrete crosstie flexural demands to different railroad track support conditions can lead to an improved understanding of crosstie flexural performance and more representative design requirements. Even though the ballast layer typically provides significant pressure distribution variability under concrete crossties, understanding these support conditions is essential for accurately predicting bending moments along the crossties, a useful metric for both design and planning of tamping activities in railroad track. To quantify the influence of support conditions on concrete crossties' bending moments, laboratory experiments were performed. New and center-cracked concrete crossties were loaded while subjected to different support conditions through the use of rubber pads designed to simulate the ballast support. Results show that bending moments at the crosstie center are quite sensitive and may even be underestimated in current U.S. design practices that do not currently allow for cracking. Additionally, findings indicate that rail seat bending moments may be overestimated in typical design practices. Finally, there was no statistically significant difference between bending moments of uncracked and cracked crossties for the investigated cracking pattern. (C) 2017 American Society of Civil Engineers.