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 111 0-2-2902
3 Mar 1969

ft = ; - v' (~) 2 + V 2 ~ 207. uu um_u___uum_u_ ____u u ___ (14)

where "v" is the average shearing stress and f, is the average compressive stress.
It may occasionally be necessary to use a superior quality concrete to resist abrasion or cavi-
tation. Refer to EM 1110-2-1602, Hydraulic Design of Reservoir Outlet Structures, for require-
ment.

(2) Rectangular box culverts.
fo' = 4000 psi or 5000 psi (except for small culvents under low fills).
f, = 0.45 fo' (max. fiber stress)
f. = 20,000 psi allowable tension based on intermediate grade steel.
The criteria for allowable shear should be that given in Report 164, "Development of Design
Criteria for Reinforced Concrete Box Culverts", University of Illinois, February 1959. The follow-
ing equations should be used in determining the u nit shearing stress:

= 11 000 (.046 + p) (12 + N/V) V f',
vp" (19 + I'/d) 4000 psi

(15)

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where v", = nominal unit shearing stress at first inclined tension cracking load, at the point of
contratlexure, psi;
V = total shear at point of contratlexure.
p = ratio of positive moment reinforcement;
N/V = ratio of axial load to shear under service loading at the point of contratlexure;
1'/, = ratio of span between points of contratlexure to effective depth.
The allowable unit shearing stress under service loading,

v = ; ::; factor:i safety' -- - - -- -- - -- - -- -- - -- - - - - -- -- -- -- -- -- -- -- - - -- - -- - -- - - (16)

where factors of safety in shear, based on the ratio of cracking load to service load, are as follows:
(a) I'/d equal to or larger than 5:
FS = 2.5
(b) l'/d less than 5 but equal to or greater than 3:
I'
FS = 1.25 + 4d

(c) I'le less than 3:
F~' = 2.0

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b. Design Procedure.

(1) General. For cast-in-place concrete conduits compute \.ertical load, We, by equations
of paragraph 4 of this manual. Determine stresses by one of the methods illustrated by plates
5, 6, 7 and 8. In computing transverse stresses, the curved-beam correction factor should be ap-
plied in calculating both steel and concrete stresses at the inside faces only of conduits with
curved shells. Values of the correction factor can be selected from tables in reference (15) or
(16).

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(2) ReinfOl'cement. Concrete cover of reinforcement should be held to a minimum of 4
inches. Where exposure conditions are favorable, a lesser cover in general conformance with the
ACI code is permissible. Consideration should b~ given to salt water effect where pertinent.
Transverse reinforcement should be supplied in both inside and outside faces. Minimum
transverse steel, even where not carrying computed stress, should be .002 bt in each face. No

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