Question

The hoist shown below consists of two bars both with Young's modulus 1800 ksi. Their cross-section geometries are also shown. The length of the BC bar ($L$) is 48 in. The maximum allowable stress magnitude for both bars is 2 ksi. Determine the maximum permissible weight $W$ that can be lifted. D B B 12 in 3 in x A 30° C 2 in 2 in B A L Cross section AA Cross section BB Z W P = W Hint: Draw the force balance at point C, and then use the forces along DC and BC to obtain the stresses carried by these two bars. The tensile stress in DC and compressive stress in BC both need to be within 2 ksi. In addition, the force in BC needs to be smaller than the critical buckling load. Answer: 2.31 kips

          The hoist shown below consists of two bars both with Young's modulus 1800 ksi.
Their cross-section geometries are also shown. The length of the BC bar ($L$) is 48 in.
The maximum allowable stress magnitude for both bars is 2 ksi. Determine the
maximum permissible weight $W$ that can be lifted.
D
B
B
12 in
3 in
x A
30°
C
2 in
2 in
B
A
L
Cross section AA
Cross section BB
Z
W
P = W
Hint: Draw the force balance at point C, and then use the forces along DC and BC to
obtain the stresses carried by these two bars. The tensile stress in DC and
compressive stress in BC both need to be within 2 ksi. In addition, the force in BC
needs to be smaller than the critical buckling load.
Answer: 2.31 kips

The hoist shown below consists of two bars both with Young's modulus 1800 ksi.
Their cross-section geometries are also shown. The length of the BC bar (L) is 48 in.
The maximum allowable stress magnitude for both bars is 2 ksi. Determine the
maximum permissible weight W that can be lifted.
D
B
B
12 in
3 in
x A
30°
C
2 in
2 in
B
A
L
Cross section AA
Cross section BB
Z
W
P = W
Hint: Draw the force balance at point C, and then use the forces along DC and BC to
obtain the stresses carried by these two bars. The tensile stress in DC and
compressive stress in BC both need to be within 2 ksi. In addition, the force in BC
needs to be smaller than the critical buckling load.
Answer: 2.31 kips

Added by Eileen M.

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