Page 42 - Civil Engineering Formulas

r = 0.264r a + 3b a + b (approx)

9π 2 – 64 6π 2I π (R 2 – r 2 ) = 0.31r 1 (approx) a 2 I (πab – a 1 b 1 ) a = 2

R 2 + Rr + r 2 R + r 0.7854a 2 b (a + 3b)t (approx)

= 0.1908r 3 = 0.2587r 3 = 0.4244r 4 3π R – c 1 πa 2 b = 4 π a 4

I c 2 I c 1 c 1 = c 1 = c 2 = I = c
I c
r)
– is very small 0.7854a 3 b (approx)
8 9π r + (a 3 b – a 1 3 b 1) (a + 3b)t
_ 0.283R 2 r 2 (R R t =
π 8 = 0.1098r 4 I = 0.1098 (R 4 – r 4 ) = 0.3tr 1 3 (approx) when r 1 πa 3 b 4 a 2
I = r 4 – I = π I = 4 π = 4

r R a (Continued)
r 1
t
a
b
r
b t
FIGURE 2.1
t b 1
2
2
c
c
1
1
c
c
1
a
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