2013 Session: 501

• Simulation-Based Rail Transit Optimization Model
  Abstract: A bi-level optimization process is proposed for determining the depth of a dipped vertical alignment (DVA) between rail transit stations as well as the cruising speed for each direction. This model also considers how regenerative braking may affect vertical alignment decisions. The optimized depth and directional cruising speeds are jointly obtained in a numerical example. Sensitivity analysis shows that regenerative braking reduces total cost, but does not significantly change the optimized DVA depth. The developed model is more realistic and useful than previous ones because it allows unequal station elevations, jointly optimizes decision variables, and considers regenerative braking.
  Authors: Kim, Myungseob; Schonfeld, Paul; Kim, Eungcheol
  Authors: Kim, Myungseob; Schonfeld, Paul; Kim, Eungcheol
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-1196
  Practice-Ready: Yes
• Discrete Element Method for Simulating Ballast Shear Strength from Large-Scale Triaxial Tests
  Abstract: Railroad ballast layer consists of discrete aggregate particles and the Discrete Element Method (DEM) is the most widely adopted numerical method to simulate the particulate nature of ballast materials and their particle interactions. Large scale triaxial tests performed in the laboratory under controlled monotonic and repeated loading conditions are commonly considered as the best means to measure macroscopic mechanical properties of ballast materials, such as strength, modulus, and deformation characteristics, directly related to load carrying and drainage functions of ballast layer in the field. This paper describes a DEM modeling approach of railroad ballast with realistic particle shapes developed from image analysis to simulate large scale triaxial compression tests on a limestone ballast material. The ballast DEM model captures the strength behavior from both the traditional slow and rapid shear loading rate type monotonic triaxial compression tests. The experimental study indicates that the shearing rate has insignificant influence on the results of triaxial compression tests. The results also show the “incremental displacement” approach captures the measured shearing response yet can save significant computational resource and time. This study has shown that the DEM simulation approach combined with image analysis has the potential to be a quantitative tool to predict the ballast performance.
  Authors: Qian, Yu; Lee, Seung Jae; Tutumluer, Erol; Hashash, Youseff; Mishra, Debakanta; Ghaboussi, Jamshid
  Authors: Qian, Yu; Lee, Seung Jae; Tutumluer, Erol; Hashash, Youseff; Mishra, Debakanta; Ghaboussi, Jamshid
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-4102
• Mechanical Properties of Polyurethane-Stabilized Ballast and Infrastructure Materials
  Abstract: Between 1980 and 2008, traffic on Class 1 railroads has increased 93% and total track length has decreased 42%, leading to a substantial increase in traffic density and maintenance requirements. To improve maintenance techniques for problematic railway elements (i.e., bolted rail joints, intersections, bridge approaches, etc.), an in situ method involving polyurethane reinforcement of the ballast layer is proposed. Ever increasing volume, tonnage, and speeds on our nation’s rail system are stressing rail substructure to levels never before evaluated or considered in depth. Ballast is a crucial material for structural support of rail tracks and trains. The structural integrity of seriously fouled ballast (i.e., containing fine particles) can be compromised leading to track instability and ultimately, train derailments. An application using polyurethane void filling and particle bonding technology has been developed and has the potential to mitigate impacts of ballast fouling, enhance rail freight capacity, and improve track-substructure maintenance efficiencies. The purpose of this paper is to present the mechanical properties of PSB (e.g., compressive and flexural), compare these properties to other materials commonly used in transportation infrastructure (e.g., natural aggregates, cement-stabilized soil, etc.), and address the suitability of PSB for use in track-infrastructure. PSB has mechanical properties similar to CSM (i.e., flexural strength), but much greater than ballast (i.e., compressive strength), which is critical for the benefit of stabilization in track-substructure. The ease of injections and negligible curing period for PSB makes it an attractive alternative for railway maintenance, especially for time-sensitive maintenance activities, such as intersections and bridge approaches.
  Authors: Keene, Andrew Kenneth; Edil, Tuncer B.; Tinjum, James M.
  Authors: Keene, Andrew Kenneth; Edil, Tuncer B.; Tinjum, James M.
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-4262
• Modeling and Field Verification of Dynamic Impact in Railroad Bridges
  Abstract: The freight railroad system in the United States facilitates large volume of freight movement cost-effectively. However, recent increase of railcar weight limits from 263,000 lbs (1170 kN) to 286,000 lbs (1272 kN) raised concerns for existing bridges on the passenger rail systems which are occasionally used by many freight railcars. As part of the load rating and evaluation process, there is a need to understand the overall dynamic behavior and the impact of the freight railcar weight on typical bridges.In this paper, a two-dimensional (2-D) dynamic model and field tests were adopted to develop a refined methodology for evaluating the performance of railroad bridges with particular emphasis on the dynamic impact. The field study included instrumentation and testing of various types of bridges under moving freight and passenger railcars and monitoring their dynamic responses (deflection, velocity and strain). Field test results were analyzed to obtain the bridges’ natural frequency and the damping ratio. The bridge structure is modeled as a Bernoulli-Euler beam and the moving train is modeled using rigid-body dynamics method. Modal superposition method is adopted to compute the dynamic interaction of the train-bridge system. The dynamic model was validated with results from the field tests. Using these model simulations, a parametric study is performed to identify the effects of various parameters (such as vehicle speed, girder stiffness, damping ratio of girder, and track roughness) on the impact factor. Results show that the AREMA code overestimates the impact factor for these bridges at normal operating speed.
  Authors: Nassif, Hani; Lou, Peng; Wang, Ying-Jie; Hwang, Eui-Seung
  Authors: Nassif, Hani; Lou, Peng; Wang, Ying-Jie; Hwang, Eui-Seung
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-4635
• Track Stiffness Transition Zone Studied by Three-Dimensional “Sandwich” Track Model
  Abstract: When railroad tracks pass from an earthen subgrade to a bridge the tracks become uneven. In fact, regardless of being level at the time of construction, over time a “dip” develops. This phenomenon occurs just before the bridge and is a cause of greater maintenance and poor ride quality. The track in this location typically needs resurfaced more frequently, increasing the cost for a railroad owner. The cause for this dip is believed to be the sudden change in stiffness between the subgrade and the bridge. The most commonly used approach to neutralize this sudden stiffness change is called “Stiffness Transition Zone” method. The idea is to spread out the stiffness jump from few centimeters to the length of about 30 meters by gradually changing the stiffness of the track. However, the details of the stiffness transition zone, for instance, the length, the pattern of the stiffness change, and the effect of train speed are yet to be studied. A dynamic track model called 3D “Sandwich Model” is developed in this study to properly study and compare different stiffness transition scenarios. It is concluded that in general transition zone will decrease the tie-ballast contact force. Increase in speed will increase the tie-ballast contact force both with and without transition zone. Longer transition zone is proven to be better in terms of decreasing the tie-ballast contact force. The exponentially increase in track stiffness transition zone is shown to be better than linearly increased case in decreasing the tie-ballast force.
  Authors: Huang, Hai; Brennecke, Braun
  Authors: Huang, Hai; Brennecke, Braun
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-4793
• Investigation of Material Improvements to Mitigate the Effects ofAbrasion Mechanism of Concrete Crosstie Rail Seat Deterioration (RSD)
  Abstract: To meet the increasingly stringent design and performance requirements due to increasing cumulative gross tonnages from heavy-haul freight operations, along with increased high-speed inter-city passenger rail development, improvements in concrete crosstie designs are needed. Rail Seat Deterioration (RSD) continues to be identified as one of the primary factors limiting concrete crosstie service life in North America. RSD refers to the degradation of material at the contact interface between the concrete crosstie rail seat and the rail pad that protects the bearing area of the crosstie. Industry experts consider abrasion to be a viable mechanism leading to RSD. A lack of understanding of the complex interactions affecting the severity of abrasion has resulted in an empirical design process for concrete crossties and fastening systems. The objective of this study is to quantify the abrasion resistance of concrete rail seats by using a variety of concrete mix designs and other materials relevant to the rail industry. To simulate the abrasion mechanism of RSD, a Small-Scale Test for Abrasion Resistance (SSTAR) was designed by researchers at UIUC. Additionally, a theoretical framework to model and predict abrasive wear was developed using statistical techniques. Data obtained from the SSTAR and statistical model will help the rail industry mechanistically design concrete crossties by improving the current understanding of the performance of various concrete abrasion mitigation approaches. Preliminary results show that abrasion mitigation approaches such as the addition of metallic fine aggregates (MFA), steel fibers, and the application of coatings improve the abrasion resistance of concrete specimens.
  Authors: Shurpali, Amogh A.; Edwards, J. Riley; Kernes, Ryan Gene; Liu, Xiang; Lange, David A.; Barkan, Christopher P. L.
  Authors: Shurpali, Amogh A.; Edwards, J. Riley; Kernes, Ryan Gene; Liu, Xiang; Lange, David A.; Barkan, Christopher P. L.
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-4271
  Practice-Ready: Yes
• Load Rating and Evaluation of Railroad Bridge Based on Nondestructive Testing and Finite Element Modeling
  Abstract: The Federal Rail Association (FRA) mandated an increase in freight railcar weight limits from 1170 kN (263,000 lb) to 1272 kN (286,000 lb). However, most of the railway bridges were built prior to World War II and are not designed to handle this increased railcar weight. Thus, there is a need for accurate and efficient methods to evaluate and load rate existing bridges that will reveal their actual capacities. In this study, the research approach adopted is aimed at providing an efficient method to load rate railway bridges. Three load rating methods were utilized and compared: (1) traditional method based on American Railway Engineering and Maintenance-of-Way Association (AREMA) specifications, (2) refined traditional method using data from field tests, and (3) load rating using testing data and finite element (FE) modeling. Various types of bridges were field tested and evaluated. Results from a typical railway bridge will be used to demonstrate and compare each one of the three load rating methods. For this bridge, non-destructive testing was performed. The collected responses were used to improve the traditional method and calibrate a 3-D FE model. The rating results indicated that method (1) can be relatively conservative and does not reflect the actual behavior of the structure while method (3) provided accurate results it was more tedious. It is suggested that the refined traditional method (2) be used since it provided similar accurate rating results without developing a detailed FE model.
  Authors: Nassif, Hani; Su, Dan; Lou, Peng
  Authors: Nassif, Hani; Su, Dan; Lou, Peng
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-4642
• Novel Full-Scale Test Facility for Ballastless High-Speed Railroad with Simulated Train Moving Loads
  Abstract: This paper presents a novel full-scale test facility for ballastless high-speed railroad¡¯s dynamic performance and accelerated long-term behavior under train¡¯s moving loads. A portion of ballastless high-speed railroad, which is almost identical to some part of realistic high-speed railroad in China, has been built in a model test box (15m*5m*6m) (49.2 ft*16.4 ft*19.7 ft) in Zhejiang University. A sequential loading system composed of eight high-performance hydraulic actuators is developed to exert dynamic loading on slab track at fasteners¡¯ positions to simulate train¡¯s moving loads. A theoretical model of train-slab track-subgrade dynamic interaction is applied to determine loads acting on fasteners in the experiments. The load sharing ratio of adjacent fasteners due to train wheel axle load acting on rails is found following Gaussian function distribution from the experiment data, and is applied in the load controlling in the experiments. Test data from the experiments are compared with the field measurements from the WuGuang high-speed railroad with various train speeds to verify the reliability of the proposed model test methodology. The experiments demonstrate the capacity of the developed full-scale model test facility to simulate train¡¯s moving load at high speeds which modern trains can reach. More tests will be conducted to investigate dynamic performance of high-speed railroad, both for ballasted track or ballastless slab track, and long term behavior of railroad under very large cycles of train¡¯s repeated movements.
  Authors: Bian, Xuecheng; Jiang, Hongguang; Chen, Yunmin
  Authors: Bian, Xuecheng; Jiang, Hongguang; Chen, Yunmin
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-2630
• Use of Recycled Tire Rubber to Modify Track Substructure Interaction
  Abstract: Resiliently Bound Ballast (RBB) is a new engineered material being developed as an alternative or supplement to conventional ballast for use in transit, passenger and freight railways to improve mechanical behavior, control the modulus and damping while using a recycled tire waste material. RBB is a stable mixture of standard ballast stone and tire derived aggregate (TDA) bound together with a purpose-designed resilient epoxy binder. Initial laboratory tests were conducted on 6 in (151 mm) and 10 in (254 mm) diameter specimens of two different mixes of RBB. Tests were conducted on fully bound samples as well as individual ballast particles with TDA bound to the ballast with the resilient epoxy binder. The tests included static triaxial compression tests, and dynamic cyclic triaxial tests. Static tests indicated that the addition of the TDA and epoxy resulted in an increase in cohesive strength. The dynamic tests indicated changes in modulus and damping depending upon the mixture of rock, TDA and epoxy. One proposed usage of RBB is to affix the RBB to the bottom of concrete ties to modify the interaction between the tie and the ballast material to improve ballast durability and modify resilience and damping. Box tests were conducted on a section of concrete tie with RBB attached and also without any RBB attached. The tie with a section of rail attached was vertically loaded with a sinusoidal load to model repetitive axle loading. Observations indicated that the box test without the RBB produced lower damping with increased abraded fines whereas the box test with the RBB had a higher damping with less abraded fines.
  Authors: Ho, Carlton L.; Humphrey, Dennis; Hyslip, James P.; Moorhead, William H.
  Authors: Ho, Carlton L.; Humphrey, Dennis; Hyslip, James P.; Moorhead, William H.
  Year: 2013
  Document Type: Paper
  Subject: Railroads; Rail
  Session: 501
  Paper Number: 13-3409
  Practice-Ready: Yes
• Novel Full-Scale Test Facility for Ballastless High-Speed Railroad with Simulated Train Moving Loads
  Authors: Bian, Xuecheng
  Authors: Bian, Xuecheng
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Rail
  Session: 501
  Paper Number: 13-2630
• Investigation of Material Improvements to Mitigate the Effects of Abrasion Mechanism of Concrete Crosstie Rail Seat Deterioration (RSD)
  Authors: Shurpali, Amogh
  Authors: Shurpali, Amogh
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Rail
  Session: 501
  Paper Number: 13-4271
• Modeling and Field Verification of Dynamic Impact in Railroad Bridges
  Authors: Wang, Ying-Jie
  Authors: Wang, Ying-Jie
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Rail
  Session: 501
  Paper Number: 13-4635
• Load Rating and Evaluation of Railroad Bridge Based on Nondestructive Testing and Finite Element Modeling
  Authors: Su, Dan
  Authors: Su, Dan
  Year: 2013
  Document Type: Presentation; Poster
  Subject: Rail
  Session: 501
  Paper Number: 13-4642