Hi All,

I want to know if Version 6.0 of CII does a check for the combined equivalant stress when performing underground piping analysis to check for stresses as per API 1102 ?

I understood this was in the works some years ago but I do not know if this has been incorporated in the software ?
Appreciate inputs from the experts.

The criteria of API 1102 (7th Ed.) is as follows:


"4.8.1.2 The second check for the allowable stress is accomplished by comparing the total effective stress, Seff (psi or
kPa), against the specified minimum yield strength multiplied by a design factor, F. Principal stresses, S1, S2, and S3,
(psi or kPa), are used to calculate Seff. The principal stresses are calculated from the following:
S1 = SHe + ΔSH + SHi (9)
where
S1 is the maximum circumferential stress.
ΔSH is ΔSHr, in psi or kPa, for railroads, and
is ΔSHh, in psi or kPa for highways.

S2 = ΔSL – EsαT(T2 – T1) + νs(SHe + SHi) (10)
where
S2 is the maximum longitudinal stress.
ΔSL is ΔSLr in psi or kPa, for railroads, and
is ΔSLh in psi or kPa, for highways.
Es is Young’s modulus of steel, in psi or kPa.
αT is the coefficient of thermal expansion of steel, per °F or per °C.
T1 is the temperature at time of installation, in °F or °C.
T2 is the maximum or minimum operating temperature, in °F or °C.
vs is Poisson’s ratio of steel.
NOTE Table A-3, in Annex A gives typical values for Es, vs and αT.
S3 = –p = –MAOP or –MOP(11)
where
S3 is the maximum radial stress.
NOTE The Poisson effects from SHe and SHi are reflected in S2 as vs (SHe + SHi). The Poisson effect of ΔSL on S1 is not directly
represented in the equation for S1. The values of ΔSH and ΔSL in this recommended practice were derived from finite element
analyses, thus they already embody the appropriate Poisson effects.
4.8.1.3 The total effective stress, Seff (psi or kPa), may be calculated from the following:
(12)
The check against yielding of the pipeline may be accomplished by assuring that the total effective stress is less than
the factored specified minimum yield strength, using the following equation:
(13)
S1 = SHe + ΔSH + SHi
S2 = ΔSL – EsαT(T2 – T1) + νs(SHe + SHi)
S3 = –p = –MAOP or –MOP
Seff
12
= --[(S1 – S2)2 + (S2 – S3)2 + (S3 – S1)2]
Seff ≤ SMYS × F

26 API RECOMMENDED PRACTICE 1102
where
SMYS is the specified minimum yield strength, in psi or kPa.
F is the design factor."