Posted by: M.Mohammad
EXPLAINING ABOUT B31.4 - 01/16/12 06:28 AM
Hello Dears,
I want to have explaining about below paragraph that is in Quick Reference Manual for B31.4.
Amount the pipeline may be considered under complete axial restraint, i.e. long and buried. This option is used primarily when the user is adding bending stresses to the stresses already developed in the pipeline due to its buried restraint. This condition occurs when, for example a branch is tieing into a long buried header and the soil supports are not modeled. The equation for stress in CAESAR II is:
Stress = (Fac) x abs[ Ea(T2-T1) + (1-n) Shoop ] + (SE + SL)(1-Fac)
Where:
E = elastic modulus
a = thermal expansion coefficient per degree
T2 = operating temperature
T1 = ambient temperature
n = Poisson's ratio
Shoop = hoop stress in the pipe.
SE = expansion stress due to bending
SL = sustained stress due to pressure.
Fac should be a number between zero and one. One, when the pipe is fully restrained, i.e. buried for a long distance. Zero when the pipe is subject to no buried axial restraint. The default value for Fac is 0.0. Note that when Fac is 0.001, this indicates to CAESAR II that the pipe is buried but that the soil supports have been modeled. This will cause the hoop stress component, rather than the longitudinal stress, to be added to the operating stresses, conforming to the spirit of the restrained line stress calculation above.
I want to have explaining about below paragraph that is in Quick Reference Manual for B31.4.
Amount the pipeline may be considered under complete axial restraint, i.e. long and buried. This option is used primarily when the user is adding bending stresses to the stresses already developed in the pipeline due to its buried restraint. This condition occurs when, for example a branch is tieing into a long buried header and the soil supports are not modeled. The equation for stress in CAESAR II is:
Stress = (Fac) x abs[ Ea(T2-T1) + (1-n) Shoop ] + (SE + SL)(1-Fac)
Where:
E = elastic modulus
a = thermal expansion coefficient per degree
T2 = operating temperature
T1 = ambient temperature
n = Poisson's ratio
Shoop = hoop stress in the pipe.
SE = expansion stress due to bending
SL = sustained stress due to pressure.
Fac should be a number between zero and one. One, when the pipe is fully restrained, i.e. buried for a long distance. Zero when the pipe is subject to no buried axial restraint. The default value for Fac is 0.0. Note that when Fac is 0.001, this indicates to CAESAR II that the pipe is buried but that the soil supports have been modeled. This will cause the hoop stress component, rather than the longitudinal stress, to be added to the operating stresses, conforming to the spirit of the restrained line stress calculation above.