hello all:
why there are no parameters of X80 at 0deg(B31.3) in material data base,does that mean X80 can not be used at 0deg of B31.3?
And the other question: in soil models, when both FRICTION COEFFICIENT and UNDRAINED SHEAR STRENGTH should be entered?i always enter FRICTION COEFFICIENT and left UNDRAINED SHEAR STRENGTH blank~

Do not assume that missing material data implies the material cannot be used. It is up to you to determine if the Code allows that service. You can always add you own material data for CAESAR II analysis.

On the soil modeler - specify Undrained Shear Strength for cohesive soils (clay) and specify Friction Coefficient for granular (sandy) soils.

The API 5L X-grades are typically used in B31.4 and B31.8 applications only. They have poor fatigue properties because of the cold working required to establish their high yield strengths.

Because B31.4 and B31.8 are used mainly for buried piping, thermal cycling usually does not become an issue. Also because they are buried, they are typically below the frost line, so it is unlikely that they will experience a temperature of 0 deg C (let alone 0 deg F). Also note that many of the API 5L X-grades require the use of ASTM A694 (I think) flanges, which are effectively unlisted components in B31.1 and B31.3.

All in all, this is likely to be a poor material choice for a B31.3 application, although as Dave correctly notes, it is not forbidden. There will just be a lot of extra work required in order to satisfy the Code material requirements.