DEVELOPMENT AND VERIFICATION OF A MOMENT-CURVATURE BASED RAILROAD TIE ANALYSIS PROGRAM

A study was conducted to estimate the flexural capacity of monoblock tie under practical load and various ballast support conditions through a numerical approach. The current recommended design approach is maximum allowable stresses by American Railway Engineering and Maintenance -of-Way Association (AREMA) [1]. The recommended design standard includes general design aspects (material, dimensions and loads) and structural strength and testing method for prestressed concrete monoblock tie. Considering the complexity of the tie behavior especially post-cracking and varying ballast support conditions, it is desired to capture tie performance under cyclic train traffic load. Furthermore, the effects of changes in tie geometry should be incorporated into tie design and analysis. Thus, a numerical approach based on Moment-Curvature (M- C) principle is employed for design and analysis of the flexural behavior of prestressed concrete monoblock ties. The computational tool is computing M-C curve for each slice of tie where the tie can be divided into minimum half inch slice. At this stage, the crack propagation can be observed on concrete strain diagram. Then repeating the same process of computing M-C curve along the tie, and the rotation can be determined at a particular moment. Finally, deflection of tie is calculated by using moment-area method, additionally changes in rail-seat center-to-center spacing can be defined. A verification and validation approach are employed to establish accuracy and reliability of the developed numerical program. In this paper, the program verification will be discussed. The developed code was compared with corresponding analytical solution or numerical solution at each intermediate step. There are three benchmarks used to verify the code, including hand solution, commercial finite element result, and existing tie analysis example. A small discrepancy was noted in the third case, however, the comparisons had good agreement overall.