Transactions . cear span 90 inches. Cast-Iron Keys of cross-shaped section, as useo on theRichmond, Fredericksburg and Potomac Railway. used as bridge-stringers. Fig. 40 shows dimensions of the full-sized keys used for a stringer composed of two superimposedsticks, each 9 inches wide and 15 inches deep; 9 of these bem-used in a stringer 24 feet long. The writer is indebted toPresident E. T. D. Myers for drawings and information relativeto the practice used on this road. 788 THE EFFICIENCY OF BUILT-UP WOODEN BEAMS. No. 45. Fig. 41 shows beam, and Fig. 42 the key weighed 60 pounds, bro
Transactions . cear span 90 inches. Cast-Iron Keys of cross-shaped section, as useo on theRichmond, Fredericksburg and Potomac Railway. used as bridge-stringers. Fig. 40 shows dimensions of the full-sized keys used for a stringer composed of two superimposedsticks, each 9 inches wide and 15 inches deep; 9 of these bem-used in a stringer 24 feet long. The writer is indebted toPresident E. T. D. Myers for drawings and information relativeto the practice used on this road. 788 THE EFFICIENCY OF BUILT-UP WOODEN BEAMS. No. 45. Fig. 41 shows beam, and Fig. 42 the key weighed 60 pounds, broke at 11,940 pounds. Check-pieces : B weighed 22 pounds, broke at 3370 pounds ; C weighed20 pounds, broke at 3400 pounds. Efficiency of beam, \—-Ptf-V \ / 414L > yt=- -r- [c 1^- >j Cast-Iron Key. per cent. This result is better than that shown by any otherform of key not provided with wedges, and is doubtless due tothe ample breadth of key which resists the tendency to rollover. The curve shows, ho
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
