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Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation (2010)

Chapter: Chapter 3 - Comparisons of Two Guard Rail Installation Philosophies

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Suggested Citation:"Chapter 3 - Comparisons of Two Guard Rail Installation Philosophies." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
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Suggested Citation:"Chapter 3 - Comparisons of Two Guard Rail Installation Philosophies." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
Page 7
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Suggested Citation:"Chapter 3 - Comparisons of Two Guard Rail Installation Philosophies." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
Page 8
Page 9
Suggested Citation:"Chapter 3 - Comparisons of Two Guard Rail Installation Philosophies." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
Page 9
Page 10
Suggested Citation:"Chapter 3 - Comparisons of Two Guard Rail Installation Philosophies." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
Page 10
Page 11
Suggested Citation:"Chapter 3 - Comparisons of Two Guard Rail Installation Philosophies." National Academies of Sciences, Engineering, and Medicine. 2010. Track-Related Research, Volume 7: Guidelines for Guard/Restraining Rail Installation. Washington, DC: The National Academies Press. doi: 10.17226/14347.
×
Page 11

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6To compare the two different guard rail installation philoso- phies, the TTCI NUCARS vehicle-track dynamics computer program was used to conduct steady-state curving simulations on a number of constant radii curves without perturbations to evaluate performance trends. Table 2 lists the parameters of the four types of transit vehicle models used in this project. Figure 3 illustrates their structures and layouts. Since there are no uniform definitions of “heavy rail vehicles,” “transit rail cars,” or “light rail vehicles,” this report adopts the customary definitions used by most transits, which are the following: • Heavy Rail Vehicles: They are also referred to as commuter rail and subject to FRA regulations. They normally have two trucks and examples include Metro North; LIRR; METRA (Chicago); SEPTA (Philadelphia, commuter service); CalTran (California); MARC (Baltimore); and MBTA (Boston). All these cars are designed to interact with freight traffic and are designed with the appropriate “buff load.” • Transit Rail Cars: They normally have two trucks and exam- ples include NYC Transit (subway and elevated); SEPTA (Philadelphia, subway); WMATA; MARTA; Baltimore (sub- way); CTA (Chicago, subway and elevated); Los Angeles; MBTA (Boston, subway); and BART. • Light Rail Vehicles: They normally have two trucks or three trucks with articulation. Examples include MBTA (Boston, green line); NJ Transit; Baltimore; Pittsburgh; Charlotte; MUNI (San Francisco); Denver; San Diego; San Jose (Valley); Portland; St. Louis; and SEPTA. These cars can be high floor, low floor, or a combination of both. They are formerly referred to as street cars or trolley cars. The Type 1 transit rail cars and Type 1 light rail vehicles were used for the steady-state curving simulations in this section, and all four types of vehicle models were used for the flange climb derailment simulations discussed in Section 4. All four vehicle models were similar to those used in the TCRP Phase I guard rail study (1) and the previous TCRP flange climb derailment study (2). No simulations or analyses were made for heavy rail vehicles, although the lightest weight heavy rail vehicles can have dimensions and wheel loads that are similar to the Type 2 Transit Rail Car. The Type 1 light rail vehicle represented a typical high-floor articulated vehicle composed of two car bodies and three trucks, as Figure 3(b) shows. The two car bodies articulated on the middle truck and all three trucks have solid wheel sets. The Type 2 light rail vehicle model was a typical articulated low-floor light rail transit vehicle. It was composed of three car bodies and three trucks, as Figure 3(c) shows. The end car bodies were each mounted on a single truck at one end and connected to an articulation unit at the other end. The center car body was the articulation unit riding on a single truck equipped with independent rotating wheels. The track inputs included a number of left hand smooth curves with curve radii from 100 to 955 ft and 1-in. super- elevation. The vehicle running speed was 15 mph. The W/R profile combinations used in the simulations were a 63° flange wheel for the Type 1 transit rail car and a 75° flange angle wheel for the Type 1 light rail vehicle on standard American Railway Engineering and Maintenance-of-Way Association (AREMA) 115 lb/yd rail. The W/R friction coefficient used in the simu- lation was 0.4 to avoid causing flange climb derailments. 3.1 Transit Rail Cars (Type 1) In most cases, guard rails are installed on the inside of the low rail. One function of a guard rail is to reduce excessive lateral force on the high rail by contacting the low-rail side wheel back. The reduction of lateral force on the high rail is mostly controlled by the flangeway clearance between the low rail and the guard rail, as the Phase I study (1) of this project showed. The lateral force distributions between the high rail and the guard rail are significantly different for these two guard rail installation philosophies. More than twice the lateral force acts on just the guard rail using Philosophy II, and the lateral C H A P T E R 3 Comparisons of Two Guard Rail Installation Philosophies

force acts almost equally on both rails using Philosophy I (see Figure 4). The excessive lateral force on the guard rail will result in rail and component damage and will reduce their service life. The flangeway clearance optimization methodology and benefits were investigated in the Phase I report. Figure 5 shows that installing the guard rail using Philoso- phy II results in a larger rolling resistance than does that of Philosophy I. Installing the guard rail using Philosophy I with optimal flangeway clearance could decrease the rolling resist- ance on tight curves with radii less than 250 ft. In 1982, a transit rail car was tested on TTCI’s Tight Turn Loop (TTL) (a 150-ft radius curve with 1.5-in. superelevation) track with and without restraining rails (4). The vehicle weighed 97,020 lbs and had truck center spacing of 54 ft, axle spacing of 7.5 ft, and a wheel radius of 15 in. The restraining rail case represents a condition where the wheel flange back contacts the restraining rail at a 90° angle, as Figure 6 shows. The guard rail case represents a condition where the wheel flange tip contacts the rail with a less than 90° angle, as Figure 7 shows. Even though the restraining rail was installed horizontally on the TTL track, the restraining rail height was only about 0.5 in. above the low-rail top and resulted in the contact with the wheel on the back of the wheel flange tip. Therefore, according to the definition, the TTL horizontally mounted rail with low height, as Figure 7 shows, was modeled as a guard rail because its contact angle (δ) on the wheel flange back was less than 90°. The tests showed that the traction force required to propel the car with the guard rail was about 30% higher than without the restraining rail, as Table 3 shows. The test result was consistent with the simulation result in Figure 5, which showed about a 10 to 30% traction force increase in the 100 ft and 250 ft radii curves as a result of using Philosophy II. Figure 8 shows that both philosophies resulted in a larger wear index on leading axle wheels (the sum of the wear index from all contact points on both wheels of the lead axle) than did the case without a guard rail, but there was a smaller wear index with Philosophy I than with Philosophy II. The axle steering capability was evaluated by using the axle angle of attack (AOA) on curves. Figure 9 shows that the axle 7 Parameters Transit Rail Car 1 Light Rail Vehicle 1 Transit Rail Car 2 Light Rail Vehicle 2 Carbody (Numbers) 1 2 1 3 Truck (Numbers) 2 3 2 3 (IRW in middle truck) Truck Center Spacing (ft) 52 23 47.5 24 Axle Spacing (ft) 7.3 6.3 6.8 6.2 Wheel Load (kips) 9.45 Mid truck: 5.2 End truck: 8.2 13.95 Mid truck: 5.9 End truck: 8.49 Wheel Diameter (in.) 27 27 27 27 Wheel Flange Angle (degrees) 63 75 63 75 Table 2. Vehicle modeling parameters. (a) Type 1 and 2 Transit Rail Cars (b) Type 1 Light Rail Vehicle (c) Type 2 Light Rail Vehicle Figure 3. Transit vehicles structures and layouts. 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 100 250 320 500 755 955 Curve Radius (ft) W he el L at er al F or ce (lb ) High Rail Contact, No Guard Rail Guard Rail Contact, Philosophy II High & Guard Rail Contact, Philosophy I Force on High Rail Force on Guard Rail Equal Force on Both Rails Figure 4. The wheel lateral force of a Type 1 transit rail car with a guard rail.

8High Rail Contact, No Guard Rail Guard Rail Contact, Philosophy II High & Guard Rail Contact, Philosophy I 0 500 1000 1500 2000 2500 3000 3500 100 250 320 500 755 955 Curve Radius (ft) R ol lin g Re si st an ce (l b) Figure 5. The vehicle rolling resistance of a Type 1 transit rail car with a guard rail. Figure 6. Wheel back/restraining rail contact. Guard Rail Figure 7. Wheel and horizontal guard/restraining rail installed at a low position. steering capability was not changed significantly by installing a guard/restraining rail, especially on tight curves. Both philoso- phies resulted in a slightly larger AOA on the leading axle than did the case with no guard rail; Philosophy I generated a smaller AOA than Philosophy II. This conclusion was con- firmed by the test results of the transit rail car on TTL track in 1982, as Figure 10 shows. The differences between the two guard rail installation philosophies on restraining rail applications (with a flange back contact angle of about 90°) were also investigated through simulations. Figure 11 shows that the wheel lateral force of the Type 1 transit rail car with a restraining rail had a similar trend to that of guard rail cases. However, the vehicle rolling resist- ances with restraining rail were much bigger than those of guard rail cases, except the case of 100 ft radius curves, as Figure 12 shows. Because the vehicle rolling resistance is the sum of the wear index on all wheels, a similar trend was found in the wheel wear index. As expected, Figure 13 shows that the leading axle wear index with a restraining rail was much larger than that of the guard rail cases except for the case of 100 ft radius curves. The Phase I study of this project (1) showed that the wear index increases with the contact angle. The increase of the wear index and the vehicle rolling resistance with a restraining rail is due to the high (90°) contact angle between the wheel back and the restraining rail, compared with a contact angle smaller than 80° between the wheel flange tip and the guard rail. The higher the contact angle is, the higher the spin creepage is, which leads to a higher wear index. The axle steering capability was compared by using the axle AOA in curves. Figure 14 shows that the axle steering capability was not changed significantly by installing a guard/ restraining rail, especially on tight curves. Both philosophies resulted in a slightly larger AOA on the leading axle than did the case with no guard rail, with Philosophy I generating a smaller AOA than Philosophy II. Figure 14 shows that the axle AOA of the Type 1 transit rail car with a restraining rail had trends similar to the trends of the guard rail cases; the AOA change caused by guard/restraining rail installation was negligible compared with the cases with no guard rail, regard- less of which philosophy was used. 3.2 Light Rail Vehicles (Type 1) This section compares the two guard rail installation philoso- phies with applications to the Type 1 light rail vehicle with a 75° flange angle wheel. Simulations were conducted only for a guard rail installation with a back of flange contact angle to the guard rail of less than 80°.

Figure 15 shows that the wheel lateral forces on the guard rail using Philosophy II on most curves except the 100-ft radius curve were larger than those of the cases with no guard rail. This was caused by the wheel flange tip climbing on the guard rail at the 100-ft radius curve. As a result, the high-rail contacts were close to the wheel flange root and shared part of the lateral force, which reduced the lateral force on the guard rail. Figures 15 through 18 show similar trends compared with Figures 4 through 9 for the transit rail car. The conclusions drawn from the simulations of the Type 1 light rail vehicle with 75° flange angle wheels will be the same as the Type 1 transit rail car with 63° flange angle wheels as discussed in Section 3.1. The following conclusions can be drawn from the Type 1 transit rail car and the Type 1 light rail vehicle steady-state 9 Case Location Measured Traction Force (lb) Average Traction Force (lb) Test Date 119,000 3,250 118,700 2,400 Without Guard Rail 118,700 2,500 2,716 5/11/1982 118,300 3,600 118,500 3,400 118,700 3,400 118,900 3,900 With Guard Rail 119,100 3,700 3,600 5/28/1982 Table 3. Transit vehicle traction force measurement on TTCI’s TTL track. High Rail Contact, No Guard Rail Guard Rail Contact, Philosophy II High & Guard Rail Contact, Philosophy I 0 200 400 600 800 1000 1200 1400 100 250 320 500 755 955 Curve Radius (ft) Le ad in g Ax le W ea r I nd ex (lb in ./in .) Figure 8. The wear index of a Type 1 transit rail car with a guard rail. High Rail Contact, No Guard Rail Guard Rail Contact, Philosophy II High & Guard Rail Contact, Philosophy I 0 10 20 30 40 50 60 100 250 320 500 755 955 Curve Radius (ft) A ng le o f A tta ck (m ra d) Figure 9. The axle AOA of a Type 1 transit rail car with a guard rail. 0 5 10 15 20 25 30 35 40 45 0 5 10 15 20 Speed (mph) With Guard Rail Without Guard Rail A ng le o f A tta ck (m ra d) Figure 10. Measured transit rail car leading axle AOA on TTL track. 0 2000 4000 6000 8000 10000 12000 100 250 320 500 755 955 Curve Radius (ft) W he el L at er al F or ce (lb ) High Rail Contact, No Guard Rail Restraining Rail Contact, Philosophy II High & Restraining Rail Contact, Philosophy I Figure 11. The wheel lateral force of a Type 1 transit rail car with a restraining rail.

10 High Rail Contact, No Guard Rail Restraining Rail Contact, Philosophy II High & Restraining Rail Contact, Philosophy I 0 500 1000 1500 2000 2500 3000 100 250 320 500 755 955 Curve Radius (ft) R ol lin g Re si st an ce (l b) Figure 12. The vehicle rolling resistance of a Type 1 transit rail car with a restraining rail. High Rail Contact, No Guard Rail Restraining Rail Contact, Philosophy II High & Restraining Rail Contact, Philosophy I 0 200 400 600 800 1000 1200 1800 1600 1400 100 250 320 500 755 955 Curve Radius (ft) Le ad in g Ax le W ea r I nd ex (lb in ./in .) Figure 13. The wear index of a Type 1 transit rail car with a restraining rail. High Rail Contact, No Guard Rail Restraining Rail Contact, Philosophy II High & Restraining Rail Contact, Philosophy I 0 10 20 30 40 50 60 100 250 320 500 755 955 Curve Radius (ft) A ng le o f A tta ck (m ra d) Figure 14. The axle AOA of a Type 1 transit rail car with a restraining rail. High Rail Contact, No Guard Rail Guard Rail Contact, Philosophy II High & Guard Rail Contact, Philosophy I 0 1000 2000 3000 4000 5000 6000 7000 8000 100 250 320 500 755 955 Curve Radius (ft) W he el L at er al F or ce (lb ) Figure 15. The wheel lateral force of a Type 1 light rail vehicle with a guard rail. High Rail Contact, No Guard Rail Guard Rail Contact, Philosophy II High & Guard Rail Contact, Philosophy I 0 500 1000 1500 2000 2500 3000 100 250 320 500 755 955 Curve Radius (ft) R ol lin g Re si st an ce (l b) Figure 16. The vehicle rolling resistance of a Type 1 light rail vehicle with a guard rail. High Rail Contact, No Guard Rail Guard Rail Contact, Philosophy II High & Guard Rail Contact, Philosophy I 0 100 200 300 400 500 600 700 800 100 250 320 500 755 955 Curve Radius (ft) Le ad in g Ax le W ea r I nd ex (lb in ./in .) Figure 17. The wear index of a Type 1 light rail vehicle with a guard rail.

curving simulations, regarding comparisons of the two differ- ent guard rail installation philosophies: • Philosophy I leads to a better vehicle dynamic performance than Philosophy II in terms of lower lateral forces on rails, lower vehicle rolling resistance, and lower leading axle wear. • Both philosophies lead to higher vehicle rolling resistance and leading axle wheel wear, compared with the case with no guard rail. • The axle steering capability difference between these two philosophies is negligible. • Restraining rails (the W/R contact angle is almost 90°) and guard rails (the W/R contact angle is less than 80°) provide similar trends in performance. 11 High Rail Contact, No Guard Rail Guard Rail Contact, Philosophy II High & Guard Rail Contact, Philosophy I 0 10 20 30 40 50 5 15 25 35 45 100 250 320 500 755 955 Curve Radius (ft) A ng le o f A tta ck (m ra d) Figure 18. The axle AOA of a Type 1 light rail vehicle with a guard rail.

Next: Chapter 4 - Transit Vehicle Flange Climb Derailment Simulation »
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TRB’s Transit Cooperative Research Program (TCRP) Report 71, Volume 7: Guidelines for Guard/Restraining Rail Installation explores two guard rail installation philosophies and the effects of vehicle types, wheel flange angle, wheel/rail friction coefficient, curve radius, cant deficiency, and track perturbation on flange climb derailments.

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