Transactions . uilt beam weighed 35 pounds,broke at 5900 pounds. Check-pieces: B weighed 14 pounds,broke at 2930 pounds; C weighed 14 pounds, broke at 2080pounds. Efficiency of built beam, per cent. Averageefficiency from the two tests, per cent. Owing to the peculiar construction of this beam it wasthought desirable to test two of them turned upside down. No. 0 D. Same as 0 B, except that the sticks were incheswide, and the beam was inverted. Weight of built beam, 36pounds; broke at 5700 pounds. Check-pieces: B weighed 15pounds, broke at 3500 pounds; C weighed 14 pounds, brokeat
Transactions . uilt beam weighed 35 pounds,broke at 5900 pounds. Check-pieces: B weighed 14 pounds,broke at 2930 pounds; C weighed 14 pounds, broke at 2080pounds. Efficiency of built beam, per cent. Averageefficiency from the two tests, per cent. Owing to the peculiar construction of this beam it wasthought desirable to test two of them turned upside down. No. 0 D. Same as 0 B, except that the sticks were incheswide, and the beam was inverted. Weight of built beam, 36pounds; broke at 5700 pounds. Check-pieces: B weighed 15pounds, broke at 3500 pounds; C weighed 14 pounds, brokeat 3200 pounds. Efficiency of built beam, per cent. No. 0 E. Same as 0 D. Beam weighed 32 pounds, broke at4750 pounds. Check-pieces: B weighed 13 pounds, broke at2670 pounds; C weighed 14 pounds, broke at 2880 of built beam, per cent. Average of 0 D and0 E, per cent. Diagram 3 shows that the first two beams started very well, THE EFFICIENCY OF BUILT-UP WOODEN BEAMS. 751 Diagram Rankines and Brunels horizontal space=H2 inch deflection. 752 THE EFFICIENCY OF BUILT-UP WOODEN BEAMS. but as the load increased the deflection became marked. Thiswas wholly due to the straightening out of the bolts. Thebest result was got from beam No. 0 D, which was inverted, sothat the bolts drew tighter as the loads increased. On theother hand, No. 0 E gave the worst results. The low efficiencies speak for themselves. They are due tothe fact that as the bolts drew more and more near the perpen-dicular position the component sticksslid upon the inclinedfaces of the keys, and sprung the joint open three-eighths of aninch before the beam failed. This caused excessive deflectionunder high loads, and prevented the usual fractional resistancesbetween the surfaces of the component sticks from coming intoplay. The writer, therefore, fails to see any merit in Eankines Fig. 13. k gl ^ -7—->j)< -7- * 6—H II i f rx%° —4—?!? „ 4 B. 1 Clear span=66
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
