Page 34 - Civil Engineering Formulas

Radius of gyration R a 2 − 6R 2 ≈ 2 24 a 2 + 12r 2 48 + 2b 1 2 + 12bb 1 12b 2 + b 1 ) 6 (2b

h

h 2 b 1 2
Section modulus I r I 180° cos R n AR (approx) 4 + 6bb 1 + + 2b 1 ) 12 (3b

I = c = = 6b 2 =
I c

h 3 b 1 2
Moment of inertia a 2 ) − (6R 2 a 2 ) + (12r 2 (approx) + 6bb 1 + b 1) + 36 (2b 2b 1 + 3b h b 1 + 2b

= A 24 A = 48 AR 2 = 4 6b 2 I = 1 c = 3
I h Geometric properties of sections.

Equilateral polygon A = Area R = Rad circumscribed circle n = No. of sides a = Length of side of octagon c b 1 2 FIGURE 2.1
Section r = Rad inscribed circle Axis as in preceding section b b 1 2

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