Transactions . nds. & ^ This beam failed in a previously known flaw on the tension-side before there was any appreciable stress brought to bear onthe keys. The friction of the pieces caused by the pressuredue to bolts took up most of the stress. The failure of thebeam is due to the flaw alone, hence the breaking-strengthin tins case affords no basis for computing efficiency of thejoint. The test is reported merely for sake of the deflection-curves. No 24 Everything exactly as in No. 20, except that beamweighed 36 pounds. Broke at 8660 pounds. Check-pieces: 770 THE EFFICIENCY OF BUILT-UP WOODEN
Transactions . nds. & ^ This beam failed in a previously known flaw on the tension-side before there was any appreciable stress brought to bear onthe keys. The friction of the pieces caused by the pressuredue to bolts took up most of the stress. The failure of thebeam is due to the flaw alone, hence the breaking-strengthin tins case affords no basis for computing efficiency of thejoint. The test is reported merely for sake of the deflection-curves. No 24 Everything exactly as in No. 20, except that beamweighed 36 pounds. Broke at 8660 pounds. Check-pieces: 770 THE EFFICIENCY OF BUILT-UP WOODEN BEAMS. B weighed 16 pounds, broke at 1780 pounds; C weighed 18pounds, broke at 2200 pounds. Efficiency of beam, per cent. This high efficiency is probably due to the fact that check-piece B was the weakest of the four pieces cut out of the sameplank; still, there was no apparent difference between A andB. This case shows the impossibility of getting material per-fectly homogeneous throughout, Fig. 26. Joggled Beam with sticks blocked apart. No. 25. Everything exactly the same as No. 20, except thatkeys were 3x2 inches and the two sticks were held fifteen-six-teenths of an inch apart in center by Norway-pine strips. (SeeFig. 26.) Weight of beam, 40 pounds. Broke at 8910 pounds. r7i—r~ TTI /lI X +—tiw—XW+- J. Lt_J Si—i- \l I I, -1 tm- -^W-\—7M- 9=E -£p- -C3- ii -H— ?*? -EZH I Clear span = 10S- Joggled Beam in three pieces. -LZj- ? ii ?>> li Check-piece weighed 14 pounds, broke at 2400 one was used, the other having had a flaw, due to use ofcant-hook. Efficiency of built beam (on basis of solid beam deep), per cent. Diagram 8 shows deflections forbeams Nos. 25 and 26. No. 26. Exactly like No. 25, except that beam weighed 38pounds. Broke at 7170 pounds. Check-pieces : A weighed12 pounds, broke at 2220 pounds; B weighed 12 pounds, THE EFFICIENCY OF BUILT-UP WOODEN BEAMS. 771 Diagram 8. M
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
