Problem 5.7-2A tall signboard is supported by two verticalbeams consisting of thin-walled, tapered circular tubes (seefigure). For purposes of this analysis, each beam may berepresented as a cantilever ABof length L5 8.0 m subjected to a lateral load P5 2.4 kN at the free end. The tubes haveconstant thickness t 5 10.0 mm and averagediameters dA5 90 mm and dB 5 270 mm at ends Aand B, respectively. Because the thickness is small compared to the diameters,the moment of inertia at any cross section may be obtained from the formula I 5 pd3t/8 (see Case 22, Appendix D), andtherefore the section modulus may be obtained from the formula S 5 pd2t/4.At what distance xfrom the free end does the maximumbending stress occur? What is the magnitude smaxof themaximum bending stress? What is the ratio of the maximumstress to the largest stress sBat the support? Solution 5.7-2Tapered circular tube322CHAPTER 5Stresses in Beams (Basic Topics)WindloadP= 2.4 kN
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