. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . \ -—»— / P = = load on ont J rail --«__ vl^ L oads 0 ver ti€ s 1 --.^ ^ 85-lb; 6x8x8 tie; 21 stone ballast; before tamping Fig. 217.—Teack Depression Profiles, Static Load on One and Two Axles. no difference whether the load is directly above a tie or betweentwo ties. The curves are substantially identical, merely movedalong as the load moves. The amount of the depression for agiven load varies with the character of
. Railroad construction, theory and practice; a text-book for the use of students in colleges and technical schools, and a hand-book for the use of engineers in field and office . \ -—»— / P = = load on ont J rail --«__ vl^ L oads 0 ver ti€ s 1 --.^ ^ 85-lb; 6x8x8 tie; 21 stone ballast; before tamping Fig. 217.—Teack Depression Profiles, Static Load on One and Two Axles. no difference whether the load is directly above a tie or betweentwo ties. The curves are substantially identical, merely movedalong as the load moves. The amount of the depression for agiven load varies with the character of the ballast and the tamp- §540. STRESSES IN TRACK. 599 ing, whether recent or old, as was shown by the numerous othersimilar profiles given in the report. The effect of recent tamp-ing was investigated and it was shown that the depression undera load on recentlj^ tamped track is nearly proportional to theloading, which implies a nearly constant modulus of elasticityof rail support. On the other hand, if track has not been tampedfor several months, there is a comparatively deep depressionfor the first 5000 lbs., proportionately less for the next additional 25,000. 0 depression in inches O—O Before Tamping o a After Tamping Fig. 218.—Tie Depression Diagram, Static Loads, 6000 lbs., and perhaps still less for additional increments. Thisis also shown by Fig. 218, which shows the after tampingcurve to be nearly a straight line; the before tamping curveis much more curved. It should be noted that the beforetamping depression line is nearly a straight line after it is loadedto about 10,000 lbs. In later investigations this fact was utilizedby producing this nearly straight line back to the line of zeropressure, as shown by the dotted line. The intercept on theline of zero wheel-load is a measure of the depression of the tiebefore it has its full bearing on the ballast. As a partof the 600 RAILROAD CONSTRUCTION. § 54l. investigati
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Keywords: ., bookauthorwebbwalt, bookcentury1900, bookdecade1920, bookyear1922
