FLOOD06430

• County: Statewide
• Basin: Statewide
• Title: Conduits, Culverts and Pipes
• Date: 3/3/1969
• Prepared By: US Army Corps of Engineers
• Floodplain - Doc Type: Educational/Technical/Reference Information

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EM 1110--~2902
S Mar 1969

more than No. 8 at 12 inches in each face should be used unless required by computed stress.
Compression reinforcement in excess of the above cited minimum should not generally be used.
Longitudinal reinforcement should be supplied in both faces of the conduit. The area pro-
vided should be not less than 0.001 times the nominal area of concrete in each face, with a maxi-
mum of No. 6 at 12 inchea in each face. Generally the same reinforcement will be in each face
except in unusual cases. Maximum spacing of bars should be limited to 18 inches.
(3) Calculation of Transverse Reinforcement. After determining the maximum moments,
thrusts and shears, cast-in-place conduits must be designed for bending moment combined with
thrust. This may be accomplished by the transformed-section method given below.

N

1='0>!:
{

fc

=M/N
5 =kd

(S-d'J
S/ 2nfc

(d-SJ nt.
5 c

/:

Jd:1

d

o

Fig. 1. Typical Stress Diagram-Working Stres. De8ign

In figure I, the moment and thrust are replaced by the thrust, N, located at a distance,
e, from the center of the section. Equation (17) is developed from zero summation of moments
about N:

-+ bf,8 (8/3 + e.) + (8 ~ d') (2n - 1)f,A', (d' + eo) - (d; 8)nf,As (d + e.) = 0__ (17)

Values must be assumed for A. and N. and b set equal to 12". Equation (17) is then solved for 8 by
trial and error. When N falls inside the section but outside the kern, e. becomes negative in equa-
tion (17). Knowing S, f, is found from the following equation based on zero summation of normal
forces:

.J.. bf8 + (8 - d')(2n -1)f,A'. _(d - 8)nf,A. = NF* ____________________________(18)
2' 8 8
or f = NF* -- -- -- -- - - -- - - -- -- - - -- -- -- - - -- - -- (19)
, ~ + C ~ d') (2n - 1) A'. _ (d ; S) nA.

*Apply curved-beam correction factor, F, at inside face only of conduits with curved shells-see paragraph
5b(1).

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