. The action of materials under stress; . nent of the ten-sion in main tie, which slopes at 45°, is 40,000 lbs. The verticalplates of the chord are 12 in. apart, the two ties 9^ in., and theside plates of the post, 8 in. If/ for bending is 20,000, what isthe diameter of the pin ? Will the plates need reinforcing, if j^in thick? CHAPTER XIII. ENVELOPES, 225. Stress in a Thin Cylinder.—Boilers, tanks andpipes under uniform internal normal pressure of / per. Conceive a thin cylinder, of radius r,, to be cut by anydiametral plane, such as the one represented in Fig. 85, andconsider the eq
. The action of materials under stress; . nent of the ten-sion in main tie, which slopes at 45°, is 40,000 lbs. The verticalplates of the chord are 12 in. apart, the two ties 9^ in., and theside plates of the post, 8 in. If/ for bending is 20,000, what isthe diameter of the pin ? Will the plates need reinforcing, if j^in thick? CHAPTER XIII. ENVELOPES, 225. Stress in a Thin Cylinder.—Boilers, tanks andpipes under uniform internal normal pressure of / per. Conceive a thin cylinder, of radius r,, to be cut by anydiametral plane, such as the one represented in Fig. 85, andconsider the equilibrium of the half cylinder, which is illus-trated on the left. It is evident that, for unity of distancealong the cylinder, thetotal pressure on the di-ameter, 2 pr, must balancethe sum of the componentsof the pressure on thesemi-circumference in adirection perpendicular tothe diameter. This pressure 2 pr, uniformly distributed overthe diameter, must cause a tension T in the material at eachend to hold the diameter in place. Hence. T = pr. As all points of the circle are similarly situated, the tension inthe ring at all points is constant, and equal to pr. If thethickness is multiplied by the safe working tension /per squareinch, it may be equated with pr, giving. Required net thickness = ^r -^ f. In a boiler or similar cylinder made up of plates an increaseof thickness will be required to compensate for the rivet a is the pitch, or distance from centre to centre, of consecu-tive rivets in one row along a joint, and d the diameter of therivet hole, the effective length a to carry the tension is reduced 2l8 STRUCTURAL MECHANICS. to a — d, and the gross thickness of plate must not be lessthan <_. / a — d Example.—T\i^ circumferential tension in a boiler, 4 ft. diam., carrying 120 lbs. steam pressure is 120 . 24 = 2,880 lbs. per liiiear inch of length of shell, which will require a plate 2,880 . , . T . , ., ^. , m. thick (net), it / is not to exceed 10,00
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectstrengt, bookyear1897
