Cyclopedia of architecture, carpentry, and building : a general reference work . tof the beam, 2. What is the safe load for a white pine beam 9 feet longand 2 X 12 inches in cross-section, if the beam rests on end supportsand the load is at the middle of the beam, the workino- fibrestrength being 1,000 pounds and the shearing strength 50 poundsper square inch. The ratio of the length to the depth is less than 10; hencethe safe load depends on the shearing strength of the materialCalling the load P, the maximum externj^l shear (see Table B,page 55) equals ^ P, and the formula for greatest shear
Cyclopedia of architecture, carpentry, and building : a general reference work . tof the beam, 2. What is the safe load for a white pine beam 9 feet longand 2 X 12 inches in cross-section, if the beam rests on end supportsand the load is at the middle of the beam, the workino- fibrestrength being 1,000 pounds and the shearing strength 50 poundsper square inch. The ratio of the length to the depth is less than 10; hencethe safe load depends on the shearing strength of the materialCalling the load P, the maximum externj^l shear (see Table B,page 55) equals ^ P, and the formula for greatest shearing unitstress becomes 3 i P50 = -2X WT2 °^ ^ ^ *^^*^ pounds. EXAMPLES FOR PRACTICE. 1. What size of wooden beam can safely sustain loads as inFig. 12, with shearing and fibre working strength equal to 50 and1,000 pounds per square inch respectively ? Ans. 6 X 12 inches 2. What is the safe load forsa wooden beam 4 X 11 inches,and 18 feet long, if the beam rests on end supports and the loadis uniformly distributed, with working strengths as in example 1 ? Ans. 3,730 pounds 90. m a^g o ^ To lata 190 Q 3 .aSfe-^ i-I 3 < daiss to ^ 3os2 .3 g- o C/J c^ t-J OJ ?5 b .*: «a () O <u « S U _ s-Oo M « 2: STRENGTH OF MATERIALS 81 73. Kinds of Loads and Beams. We shall now discuss thestrength of beams under longitudinal forces (acting parallel tothe beam) and transverse loads. The longitudinal forces aresupposed to be applied at the ends of the beams and along the axis*of the beam in each case. We consider only beams resting onend supports. The transverse forces produce bending or flexure, and thelongitudinal or end forces, if pulls, produce tension in the beam;if pushes, they produce compression. Hence the cases to be con-sidered may be called Combined Flexure and Tension andCombined Flexure and Compression. 74. Flexure and Tension. Let Fig. 43, a, represent a beamsubjected to the transverse loads L,, L„ and L,, and to two equalend pulls P and P. The reactions Rj and R, ar
Size: 1370px × 1825px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1900, booksubjectarchitecture, booksubjectbuilding
