Structural Engineering in Railroad Track

The assignment for this week's blog was to review another professional article about structural engineering, but I want to go above and beyond, and because of my final project's focus, I couldn't help. Because I'm able to look at a drawing and see words for each line or curve, I believe I can loosely interpret this as an "article."

Pennsylvania Railroad standard plan for ballasting railroad track

Years ago, when railroads were still laying track, they developed standard plans for their methods of doing so properly and according to conditions. These plans specifically show how railroad track is to be laid and ballasted (have supporting and draining rocks put around it) for optimum performance. In the drawing above, we see the diagram for track in a cut (where rock or earth surrounds the tracks on one or both sides), as well as the diagram for track on a fill (where the earth slopes downward away from the track).

The top drawing, the one for track in a cut, shows specific dimensions that are determined on-site. These dimensions are then plugged into the table on the bottom-left of the plan to determine the physical location of the tracks, the ditches, the ballast, and the earth around the tracks. On the top drawing, beneath the track, the different text denotes which parts of the track sections are supposed to be made of cinder sub-ballast, and ballast (the jagged, rocky part). When looking beside the word "ultimate," we can determine that 1/2" of space is between the top of the ballast and the top of the crosstie (the large, white section that keeps the track the same distance apart). By following the line from the top of the 1/2" dimension, we see that the maximum height from the top of the tie to the top of the sub-ballast is to be 2'-3".

Continuing down and right, we see specific dimensions and slopes for the railroad's ditch. "1-1/2 to 1 Angle of Repose" means that the earth's slope is to equal 1.5 proportions horizontally and 1 proportion vertically, in order to prevent major landslides and damage to the track.

By observing the bottom drawing, we can see the same information for track in a fill. Now, why are these slopes and dimensions important? Structural engineers for the Pennsylvania Railroad determined that based on the weight of a train and how that weight travels throughout what it's standing on, these minimum dimensions were necessary to prevent major damage, loss of millions of dollars, and worst of all: loss of life. By using these standards (which varied from railroad to railroad), safety was kept at the top of the list of concerns, more freight was moved successfully, and structural engineers (as well as calculus teachers) kept their jobs.

Again, I apologize for not reviewing an article, but writing an "article" about the "article" (photo) I found hopefully suffices. At worst, at least you learned how frustrating engineering can be.

Citation:
Pennsylvania Railroad. "Cross Section of Roadway, Stone & Crushed Slag Ballast." Chart.PRR Standard Plan. Central Region: Pennsylvania Railroad, n.d. 9761. PRR Standard Plan Index. Pennsylvania Railroad Technical and Historical Society. Web. 7 Dec. 2012.