An experimental testing of prestressed concrete monoblock ties was conducted at Kansas State University to collect load-deflection data. The experimental results were used to validate the developed tie analysis and design computational tool. Present prestressed concrete monoblock tie design specification, American Railway Engineering and Maintenance -of-Way Association (AREMA), recommends flexural test method for critical locations (rail-seat and rail-center). As commonly known that rail-seat positive and rail-center negative are the governing cases in flexural design of monoblock ties. Considering the cross-section is generally reduced at center region of tie, the capacity that could be sustained is relatively smaller compared to rail-seat. Additionally, the center bound boundary condition induces large negative bending moment at center region of the tie. Thus, rail-center negative bending test was selected.
A four-point bending testing setup followed AREAMA 2020 Chapter 30 Part 4 Section 18.104.22.168 . In total 10 tests were conducted, ties selected for the test include three ties that were retired from service and seven virgin ties. The vertical deformation was measured, collecting by Keithley series 2750 data acquisition system. A 5-power magnifying glass was recommended to observed crack. Load control loads were applied until first crack, and the displacement control loads were applied.
The load-deflection results at rail-center were used to compare with the estimation computed by developed computational tool. A total of 9 comparisons were made. There were seven virgin ties (CXT type) and two post-service ties (Type-F). To eliminate uncertainties resulting in discrepancy, it is desired that the program inputs follows as closely as possible to the validation benchmarks. Cross-section properties of CXT type tie used in the analysis program, and it was measured by previous researcher at K-state. Type-F tie cross-section were measured at each shape change point. The concrete compressive strength was determined by conducting experiments following ASTM C42/C42M 2020 standards. Additionally, the Young’s modulus of elasticity was defined through best fitting to the elastic region of experimental load-deflection results at rail-center. Then, the load-deflection curves were computed and compared with experimental outcomes.