Question

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Problems 97 3.8 22. Determine the effective net areas of the sections shown by using the U values given in Table 3.2 of this chapter. Assume three bolts in a line 3 L8 X 4 X 4 1 in bolts 4 in 4 in 4 in 6 in FIGURE P3-20 21. Determne the effective net area of the MC12 X 40 shown. Assume the holes are for 7/8 in bolts. (Ans. 9.02 in it

Answer 1

For L8x4x3/4, gross area (A_g) = 8.44 in²

Bolt diameter = 1 in

Nominal hole diameter = 1 + 1/16 = 17/16 in

Hole diameter for calculating net area = 17/16 + 1/16 = 9/8 in

Net section area (A_n) = A_g - 9/8 x 3/4 = 8.44 - 9/8 x 3/4 = 7.596 in²

Effective net area (A_e) = U A_n

where U is reduction factor.

U = 1-x'/L $\leq$ 0.9

where x' is the distance from the centroid of the connected area to the plane of the connection, and L is the length of the connection.

x' = 4 - 2.95 = 1.05 in

L = 8 in

U = 1-x'/L = 1 - 1.05/8 = 0.869

Effective net area (A_e) = U A_n = 0.869 x 7.596 = 6.56 in²