Shear Stress in Beams

Example: * (continued)

Next calculate the first moment of the area, Q, for locations 2 and 3. See the figures below.

For location 2: For location 3:

At location 2: Q = A’y_bar = (2.5)(8)(3.75) = 75 in³

At location 3: Q = A’y_bar = (5.0)(8)(2.50) = 100 in³

Recall: τ = VQ/It In this example V = 2700 lb, I = (1/12)bh³ = 666.66 in⁴

and t = 8 in

So τ₂ = (2700)(75)/[(666.66)(8)] = 37.97 psi = τ₄

and

τ₃ = (2700)(100)/[(666.66)(8)] = 50.63 psi

Click here to continue with this example.

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