Question

# For a bolted assembly with six bolts, the stiffness of each bolt is kb=3 Mlbf/in and...

For a bolted assembly with six bolts, the stiffness of each bolt is kb=3 Mlbf/in and the stiffness of the members is km=12 Mlbf/in per bolt. An external load of 85 kips is applies 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.
a) determine the yielding factor of safety.
np=
b) determine the overload factor of safety.
nL=

External Load applied (P) = 80 kips

Bolt stiffness (kb) = 3(106) lbf / in

Member stiffness (km) = 12(106) lbf / in

Diameter of bolts (d) = 1/2 in - 13 UNC grade 8

Number of bolts = 6

For Unified Screw Threads UNC and UNF

Tensile stress area (At) = 0.1419 in2

SAE specifications for steel bolts for grade 8,

we have

Minimum proff strength (Sp) = 120 kpsi

Minimum tensile strength (Sut) = 150 kpsi

Load bolt (P) = kips = 13.33 kips

given by,

Stiffness Constant

a) Yielding Factor of Safety is given by,

b) Overload Factor of Safety is given by,

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