Rural Railroad Safety Center (RRSC)
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Provides railroad industry workforce development and safety research
Institutions:
- -Kansas State University
- -University of Nebraska, Lincoln
- -University of Florida
- -Pennsylvania State University, Altoona
- -California State University, Chico
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Recent Submissions
Item Open Access Track Performance in Tunnels and Rail Transition Areas with Under Tie Pads and Under Ballast Mats(Rural Railroad Safety Center, Kansas State University., 2022-06-01) Riding, Kyle A.; Bridge, Jennifer A.; Davis, Justin R.; Guan, Shanyue; Gonzalez, StephenRailroads have begun to use under tie pads (UTP) and under ballast mats (UBM) in rail track construction to reduce maintenance costs by better distributing loads, reducing the track modulus, and increasing ballast contact areas with ties. Locations such as tunnels, bridges, and bridge approaches are especially strong candidates for UTP and UBM use due to the high support stiffness they provide to the ballast. In this study, the University of Florida (UF) instrumented the Virginia Avenue Tunnel in Washington D.C., which uses UTP and UBM, during construction to monitor track pressure distribution, tie movement, and tunnel floor vibration during the first 20 months of use (July 2018 – February 2020). Track pressure distributions across ties were measured for hundreds of trains at the tunnel floor transition area and inside the tunnel. Measurements showed that the track settlement occurred over the first 6 months of measurement after track was opened, after which it stabilized to less than 0.157 in. (4 mm).Item Open Access A Wire Indent Profiling System for the Assessment of Bond and Splitting Propensity of Prestressing Wires Used in Pretensioned Concrete Railroad Ties(Rural Railroad Safety Center, Kansas State University., 2021-04-01) Beck, B. Terry; Robertson, Aaron A.; Peterman, Robert J.; Riding, Kyle A.The focus of this research was the creation of an automatic non-contact laser-based indent profiling system for the purpose of rapidly assessing geometrical characteristics of indented wires used in the manufacture of pretensioned concrete railroad ties. The process of measuring indent geometrical characteristics by traditional means is a time-consuming process which severely limits the frequency of testing and prevents statistically relevant sample sizes. In parallel with concrete prism transfer length and splitting propensity testing conducted in conjunction with this project, this system was used to identify which indent characteristics were directly related to both bond and splitting propensity in pretensioned concrete ties. This report details the automation of this indent profiling system and the results obtained for many different indented wires that were currently or historically used to manufacture pretensioned concrete railroad ties.Item Open Access High Resolution 3D Optical Scanning of Crossties to Assess Cross-Sectional Parameters and the Effects of Long-Term Abrasion and Wear(Rural Railroad Safety Center, Kansas State University., 2021-03-01) Beck, B. Terry; Robertson, Aaron A.; Peterman, Robert J.; Riding, Kyle A.This report documents measurement of the 3D geometrical properties associated with prestressed concrete railroad ties that have been subject to long-term in-track loading. A commercially-available 3D laser-based optical scanning system was used to scan the surface of sampled in-service crossties to a spatial resolution of about 1-mm, resulting in a 3D solid body CAD model of each scanned tie. A high-speed algorithm was developed to process the detailed cross-section geometrical parameters to an axial resolution of 0.5 inches, achieving an overall processing time of only a few minutes. The agreement between the ideal CAD model cross-section parameters and the measured (scanned) parameters was found to be excellent. Measured crosstie cross-sectional parameters used in support of on-going FRA project work included cross-sectional area, area moment of inertia, neutral axis position, eccentricity, and shape factor.Item Open Access Effect of Concrete Composition on Splitting Cracks in Prestressed Concrete Railroad Ties: Application of Fracture Mechanics(Rural Railroad Safety Center, Kansas State University., 2021-03-01) Dastgerdi, Aref S.; Peterman, Robert J.; Beck, B. Terry; Riding, Kyle A.The effect of concrete composition on end-splitting cracks in pretensioned concrete members was investigated. Specific parameters included the effect of aggregate shape and content, water-to-cementitious (w/cm) ratio, fly ash, paste and air void content. For each mixture evaluated, prisms were load tested in three-point bending at 4000, 6000 and 8000 psi to determine the effect of concrete compressive strength on crack growth potential. Corresponding splitting tensile tests were also conducted on samples at each compressive strength for all mixtures. Results show that increasing angularity, aggregate size distribution, and decreasing w/cm ratio improve fracture toughness by as much as 28% whereas changing other parameters had little effect. All improving factors were seen to be most effective at low strengths. A statistical model predicting fracture toughness was developed, and the results correlated well with observed cracking in pretensioned concrete members.Item Open Access Developing a Prism Qualification Test to Ensure Adequate Splitting Resistance in Pretensioned Concrete Railroad Ties(Rural Railroad Safety Center, Kansas State University., 2021-03-01) Savic, Adrijana; Peterman, Robert J.; Beck, B. Terry; Riding, Kyle A.This report presents the results from research that evaluated the effect of wire indentation type, edge distance, and the strength of concrete at de-tensioning on longitudinal splitting in pretensioned concrete railroad ties. Four-wire pretensioned concrete prisms were cast with varying reinforcement types and edge distances and the resulting splitting crack lengths were carefully measured. Results showed that concrete edge distance was the most significant factor affecting longitudinal splitting cracks, with reinforcement indentation type also playing a key role. This work resulted in the successful development of a qualification test to ensure adequate splitting resistance in pre-tensioned concrete railroad ties. This test was formally adopted as section 4.2.4 in Chapter 30 of the 2021 AREMA Manual for Railway Engineering.Item Open Access Automated Optical Surface Strain Measurement System to Determine the Transfer Length in Pretensioned Concrete Railroad Ties(Rural Railroad Safety Center, Kansas State University., 2021-03-01) Beck, B. Terry; Peterman, Robert J.; Wu, Chih-HangThis report documents the advances that have been made to determine the transfer length of pretensioned concrete railroad ties using non-contact surface displacement measurements by digital image correlation. The work has culminated with two fully-functional devices that address specific needs of the industry. The first device utilizes a multi-camera method for measuring the surface strain profile on a railroad tie and determining the associated transfer length to within +/- 1.5 in. with as few as 5 independent measurements of surface strain. The work represents a practical step towards the continuous monitoring of in-plant prestressed railroad tie production, using transfer length as a quality control parameter. The second device is capable of making measurements of strain in a real-time continuously scanning/traversing (CST) manner over the entire distance range of interest on the tie associated with transfer-length development. It was shown to be capable of a strain measurement resolution of nominally about ± 20 microstrain, at traversing speeds of up to several inches per second.Item Open Access Use of 3D Non-Contact Profilometry to Quantify Indent Characteristics of Prestressing Wires Used in Pretensioned Concrete Railroad Ties(Rural Railroad Safety Center, Kansas State University., 2021-03-01) Haynes, Mark; Wu, Chih-Hang; Beck, B. Terry; Peterman, Robert J.The objective of this research was to investigate possible correlation between prestressing wire indent geometry and the performance of pretensioned concrete members fabricated with these same reinforcements. Thirteen (13) commercially available and twelve (12) custom-made reinforcement wires were evaluated. A new non-contact indent profiling system was developed to collect detailed surface profiles of the prestressing steel. New geometrical feature measurements and processing algorithms were developed to provide detailed measurement of prestressing steel according to the dimensioning and tolerancing guidelines of ASME Y14.5-2009. These geometrical features were found to have significant correlation with the transfer length and fracture propensity of concrete crossties. Models were created to predict the transfer length of concrete crossties based on the extracted indent characteristics.Item Open Access Development of Un-Tensioned Pullout Tests to Determine the Bond Quality of Prestressing Reinforcements Used in Pretensioned Concrete Railroad Ties(Rural Railroad Safety Center, Kansas State University., 2021-03-01) Arnold, Matthew L.; Peterman, Robert J.; Beck, B. Terry; Wu, Chih-HangAn experimental program was conducted at Kansas State University (KSU) to evaluate the bond characteristics of prestressing wires and strands used in the manufacture of pretensioned concrete railroad ties. Un-tensioned pullout tests were conducted using both concrete and mortar mediums. The effect of prestressing steel surface condition on bond was evaluated by testing the bond in both the as-received and cleaned condition. A pullout test was developed (and subsequently adopted as ASTM A1096) that can be used to determine the bond quality of prestressing wires that are are in pretensioned concrete members. The pullout test specimens consist of a 4 in. outer-diameter tube with a total length of 8 in. and a steel plate welded to the tube bottom. An un-tensioned wire is held concentrically in the tube while a sand-cement mortar mixture is placed and allowed to cure. Specimens are tested when compressive strength of the mortar is between 4500 and 5000 psi. Pullout test results had excellent correlation with transfer lengths of similar wires when used to manufacture pretensioned concrete railroad ties.Item Open Access Using Tensioned Pullout Tests to Determine the Bond-Slip Relationship and Splitting-Propensity of Reinforcements Used in Pretensioned Concrete Railroad Ties(Rural Railroad Safety Center, Kansas State University., 2021-03-02) Holste, Joseph R.; Peterman, Robert J.; Beck, B. Terry; Wu, Chih-HangA study was conducted to evaluate the bond and splitting propensity characteristics of 12 different 5.32-mm-diameter prestressing wires used in the production of prestressed concrete railroad ties. Establishment of the bond-slip relationship of these wires at both transfer of prestress (transfer bond) and under flexural loading (flexural bond) was necessary to enable the accurate modeling of these ties using finite elements. Transfer bond and flexural bond of various indent patterns were tested using tensioned pullout tests. Specimens of various sizes with single or multiple wires were tested to determine the effects of cover and wire quantity on bond. Results from the testing program showed 1) the tensioned pullout tests could be used to predict the transfer length of prisms made with the same reinforcement, 2) the indent geometry depth and side-wall angle are good indicators of the likelihood of specimen splitting cracks, and 3) the importance of adequate concrete cover to eliminate potential splitting cracks.Item Open Access Effect of Concrete Properties and Prestressing Steel Reinforcement Type on the Development Length in Pretensioned Concrete Railroad ties(Rural Railroad Safety Center, Kansas State University., 2021-03-03) Momeni, Amir F.; Peterman, Robert J.; Beck, B. Terry; Wu, Chih-HangA study was conducted to determine the effect of different concrete properties and prestressing steel reinforcement type on the development length and flexural capacity of prestressed concrete railroad ties. Thirteen different 5.32-mm-diameter prestressing wires and six different strands (four 7-wire strands and two 3-wire strands) were used to fabricate 4-tendon pretensioned prisms with a square cross section. A consistent concrete mixture utilizing Type III cement and a water-to-cementitious ratio of 0.32 was used for all prisms. The prisms were detensioned at concrete compressive strengths of 3500 psi, 4500 psi, and 6000 psi. Load tests revealed that there is a large difference in the development length for different wire/strand types as well as with different concrete release strengths. Additionally, cyclic load tests revealed that there is also a significant difference in the bond performance of these reinforcement types under repeated loadings.Item Open Access Evaluation of the Remaining Prestress Force and Center Negative Capacity of Ties Removed from Track after 25 Years(Rural Railroad Safety Center, Kansas State University., 2021-03-01) Scott, James D.; Peterman, Robert J.; Beck, B. Terry; Riding, Kyle A.A study was conducted to determine the amount of internal prestress force remaining in prestressed concrete railroad tie designs that have withstood a lifetime of service without problems. Twelve (12) different tie designs that had performed well in track for over 25 years with no signs of longitudinal splitting were evaluated. Four different experimental test methods were used to determine the remaining prestress force in these existing ties. These included the flexural crack reopening method, the newly developed direct tension method, the strain gage method, and measurement of the length change of wires extracted from the ties. Test results indicate that the direct tension test was the most accurate of the four methods, and that existing ties tended to have prestressing forces in the range of 82-93 kips.Item Open Access A Comprehensive Study of Prestressing Steel and Concrete Variables Affecting Transfer Length in Pre-Tensioned Concrete Crossties(Rural Railroad Safety Center, Kansas State University., 2021-02) Bodapati, Naga N.B.; Peterman, Robert J.; Beck, B. Terry; Wu, Chih-Hang; bobA comprehensive study was conducted to determine the variation of transfer length in pretensioned prestressed concrete railroad ties with varying prestressing steel types and concrete parameters. The in-depth evaluation included eighteen different prestressing reinforcement types that are employed in concrete railroad ties worldwide. The study consisted of two phases: Lab- Phase and Plant-Phase. Throughout the study, transfer lengths were determined from surface strain measurements on pre-tensioned concrete members. During the Lab-Phase, pre-tensioned concrete prisms were fabricated to replicate plant manufactured crossties. A special jacking arrangement was employed to ensure that each of the reinforcements was tensioned to the same force. Later, during the Plant-Phase, pre-tensioned concrete railroad ties were fabricated at a concrete crosstie manufacturing plant using the same reinforcements. In addition, a long-term study was conducted on plant-manufactured crossties to determine the variation of transfer length due to in-track loading.
