Question

I need help Please, third time posting this question and i keep getting the wrong answer.

Required information For a bolted assembly with six bolts, the stiffness of each bolt is kb = 2.6 Mlbf/in and the stiffness of the members is km = 15 Mlbf/in per bolt. An external load of 80 kips is applied to the entire joint. Assume the load is equally distributed to all the bolts. It has been determined to use 1/2 in-13 UNC grade 8 bolts with rolled threads. Assume the bolts are preloaded to 75 percent of the proof load. Determine the yielding factor of safety. The yielding factor of safety is 2.05 *

Answer 1

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Giyen - P= 80 kips Kb= 2.6 Mebflin Km=is Mebflin Drameter of bolts = Lin -13 UNC grade 8 No. of bolts= 6 for ļ in-13 UNC grade 8 bolts from table At = 0.1419 in Minimum proof strength Csele 120 kpst Minimum tensile strength (swt) 150 kpji load per unit bolt (P) = 80 - 13-3333 kips But preload is fi- o.fsse At -0.75 X 120 XO-1419 A = 12.771 lip

Preload stress, 61=0.75 Sp = 0.75X120 go kpsi Stiffness constant, C= kb Kot km C= 2.6 (2.6+15) C=0.1477 Yielding factor of safety бр - SPAL cptfi 2 120x0-1419 0.1477X13-3333712-771 np= 1.155