Question

For a bolted assembly with six bolts, the stiffness of each bolt is ko = 3x106 bf/in and the stiffness of the members is km = 12x106 |bf/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 12 in-13 UNC grade 8 bolts with rolled threads. Assume the bolts are preloaded to 75 percent of the proof load. a) Determine the desired preload b) Determine the yielding factor of safety. c) Determine the overload factor of safety. d) Determine the factor of safety based on joint separation. e) Determine the value of torque in units of bi.ft, assume a torque coefficient k = 0.2 to establish the desired preload. =

Answer 1

a) To determine the desired preload, we need to find 75% of the proof load for each bolt.

Proof load for a 12 in-13 UNC grade 8 bolt can be found using reference tables or engineering specifications. Let's assume the proof load is 130 kips.

Desired preload = 75% of the proof load

Desired preload = 0.75 * 130 kips

Desired preload = 97.5 kips

b) The yielding factor of safety can be calculated by dividing the proof load by the desired preload.

Yielding factor of safety = Proof load / Desired preload

Yielding factor of safety = 130 kips / 97.5 kips

Yielding factor of safety = 1.33