Page 205 - Pressure Vessel Design Manual

Design of Vessel Supports 183

Ribs a Bending stress, fi, = 0.66 Fy.

MC1
Outside Ribs fb =- I

a Combined stress.

fh
fa
-+-<l
Fa Fb

Inside Ribs

I / Inside rib

A, = a area of rib and web, in.*
Ap = pressure area, = 0.5Fe
Figure 3-58. Dimensions of outside saddle ribs and webs.

eor 1 1 1
1 rib spacing
Outside Ribs 4 = area of rib and web, in.*
=
4 a pressure area, F x e
0 Az-ial load, P.
JG;
P = B,A, l2 = moment of inertia, - C2 = 0.5Gb
12
0 Compressiue stress, fa. Figure 3-59, Dimensions of inside saddle ribs and webs.

P
fa =A, 0 Axial load, P.
P = BDAP
a Radius of gyration, r.
0 Compressive stress, fa.
P
r=g f --
a- A,
r=e
0 Slenderness ratio, e1 /r. 0 Radius of gyration, r.

ll/r =
F;, = (See App. L.)
a Slenderness ratio, &/r.
a Unit $me, f;,.
&/r =
Fr. Fa =
f,, =
0 Unit force. J;,.
a Bending moment, M.

F1,
M = 0.5f,,el1 f --
" - 2A