Railway Track & Structures - February 2009 - (Page 34) BRIDGE APPROACH SETTLING Figure 4, above. Calculated vertical tie forces from wheel loads crossing a 10,000 to 2,000 (lbs./in./in.) stiffness change. 1.0 on the vertical scale equals the static wheel load on the bridge. Figure 5, to right. Vertical wheel-rail forces at two ballast deck bridges north of Baltimore. Figure 6, bottom right. Vertical wheel-rail forces at an open deck bridge at Chester, Pa. fully loaded freight car cross a change in track modulus from 10,000 to 2,000 (pounds/inch/inch). It is well known and well documented that track surface deviations cause dynamic loads or impacts when trains pass over them and that those higher loads increase track settlement. This is how an abrupt change in track stiffness is said to cause settlement at bridge approaches. Many attempts have been made to remedy this bridge approach problem by trying to reduce the abrupt change in stiffness. Such attempts have included increasing track stiffness on the approach by using ties of gradually increasing length or by installing a concrete or asphalt pad below the ballast, or reducing the track stiffness on the bridge by installing rail seat pads. None of these methods have produced much success. This inability to eliminate the bridge approach settlement problem prompted the Federal Railroad Administration to conduct a study to examine the track stiffness difference concept to determine why its past application had been unsuccessful. A literature review was conducted and five different methods were employed to evaluate the effect of track stiffness difference in causing bridge approach track settlement and adversely affecting ride quality. A summary of the full research report findings is presented here.1 Literature review To begin the study, a search was conducted to find sources that provided credible information that quantified the stiffness difference effect at bridge ends. Many sources either restated or referred to the theory, but none provided field measurements or other valid evidence to demonstrate 34 Railway Track & Structures February 2009 www.rtands.com http://www.rtands.com
Table of Contents Feed for the Digital Edition of Railway Track & Structures - February 2009 Railway Track and Structures - February 2009 Contents On Track Industry Today Supplier News AREMA News NRC News TTCI R&D Railroads Stepping Up Use of Technology to Locate Rail Flaws Rail Lubrication Realizing Great Potential M/W Challenges: Track Settlement at Bridge Approaches Supplier Profiles Products and Literature People Calendar Advertisers Index Sales Representatives Website Directory Professional Directory Classified Advertising Chicago Perspective Railway Track & Structures - February 2009 Railway Track & Structures - February 2009 - Railway Track and Structures - February 2009 (Page Cover1) Railway Track & Structures - February 2009 - Railway Track and Structures - February 2009 (Page Cover2) Railway Track & Structures - February 2009 - Contents (Page 1) Railway Track & Structures - February 2009 - Contents (Page 2) Railway Track & Structures - February 2009 - On Track (Page 3) Railway Track & Structures - February 2009 - Industry Today (Page 4) Railway Track & Structures - February 2009 - Industry Today (Page 5) Railway Track & Structures - February 2009 - Industry Today (Page 6) Railway Track & Structures - February 2009 - Supplier News (Page 7) Railway Track & Structures - February 2009 - AREMA News (Page 8) Railway Track & Structures - February 2009 - AREMA News (Page 9) Railway Track & Structures - February 2009 - AREMA News (Page 10) Railway Track & Structures - February 2009 - AREMA News (Page 11) Railway Track & Structures - February 2009 - AREMA News (Page 12) Railway Track & Structures - February 2009 - AREMA News (Page 13) Railway Track & Structures - February 2009 - AREMA News (Page 14) Railway Track & Structures - February 2009 - AREMA News (Page 15) Railway Track & Structures - February 2009 - NRC News (Page 16) Railway Track & Structures - February 2009 - TTCI R&D (Page 17) Railway Track & Structures - February 2009 - TTCI R&D (Page 18) Railway Track & Structures - February 2009 - TTCI R&D (Page 19) Railway Track & Structures - February 2009 - TTCI R&D (Page 20) Railway Track & Structures - February 2009 - TTCI R&D (Page 21) Railway Track & Structures - February 2009 - TTCI R&D (Page 22) Railway Track & Structures - February 2009 - Railroads Stepping Up Use of Technology to Locate Rail Flaws (Page 23) Railway Track & Structures - February 2009 - Railroads Stepping Up Use of Technology to Locate Rail Flaws (Page 24) Railway Track & Structures - February 2009 - Railroads Stepping Up Use of Technology to Locate Rail Flaws (Page 25) Railway Track & Structures - February 2009 - Railroads Stepping Up Use of Technology to Locate Rail Flaws (Page 26) Railway Track & Structures - February 2009 - Rail Lubrication Realizing Great Potential (Page 27) Railway Track & Structures - February 2009 - Rail Lubrication Realizing Great Potential (Page 28) Railway Track & Structures - February 2009 - Rail Lubrication Realizing Great Potential (Page 29) Railway Track & Structures - February 2009 - Rail Lubrication Realizing Great Potential (Page 30) Railway Track & Structures - February 2009 - Rail Lubrication Realizing Great Potential (Page 31) Railway Track & Structures - February 2009 - Rail Lubrication Realizing Great Potential (Page 32) Railway Track & Structures - February 2009 - M/W Challenges: Track Settlement at Bridge Approaches (Page 33) Railway Track & Structures - February 2009 - M/W Challenges: Track Settlement at Bridge Approaches (Page 34) Railway Track & Structures - February 2009 - M/W Challenges: Track Settlement at Bridge Approaches (Page 35) Railway Track & Structures - February 2009 - M/W Challenges: Track Settlement at Bridge Approaches (Page 36) Railway Track & Structures - February 2009 - M/W Challenges: Track Settlement at Bridge Approaches (Page 37) Railway Track & Structures - February 2009 - M/W Challenges: Track Settlement at Bridge Approaches (Page 38) Railway Track & Structures - February 2009 - Supplier Profiles (Page 39) Railway Track & Structures - February 2009 - People (Page 40) Railway Track & Structures - February 2009 - Calendar (Page 41) Railway Track & Structures - February 2009 - Sales Representatives (Page 42) Railway Track & Structures - February 2009 - Website Directory (Page 43) Railway Track & Structures - February 2009 - Professional Directory (Page 44) Railway Track & Structures - February 2009 - Classified Advertising (Page 45) Railway Track & Structures - February 2009 - Classified Advertising (Page 46) Railway Track & Structures - February 2009 - Classified Advertising (Page 47) Railway Track & Structures - February 2009 - Chicago Perspective (Page 48) Railway Track & Structures - February 2009 - Chicago Perspective (Page Cover3) Railway Track & Structures - February 2009 - Chicago Perspective (Page Cover4)
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