Weld joint efficiency (Eff) reflects the certainty of burst strength. Seamless pipe has an Eff of 1.0, a longitudinal seam drops that value to numbers like your 0.85. If you do full radiography of the joint, Eff can get back up to 1.0. See how Eff (E) is used in the wall thickness calculation. A lower Eff gives a thicker wall.

Here's the help from CAESAR II:

B31.3, B31.4, B31.8, B31.11, NAVY 505, Z662 (J), BS 806 (e), CODETI (z), FDBR (vl), GPTC/192. Allowable stress (or yield stress) tables do not include Longitudinal Weld Joint Efficiencies, Eff will be ignored for the flexibility calculations. SH will be multiplied by Eff when calculating the minimum wall thickness.

So I would say enter Eff=0.85. You should see no change in allowable stress calculations but you should see a higher tmin listed in the Miscellaneous Output report and perhaps a warning from CAESAR II if your entered thickness (adjusted by mill tolerance) is too low.

Eff is not a material parameter so it should not appear in teh material data - it a fabrication parameter.

Regarding the Weld Joint Strength Reduction Factor - that's for reducing the strength of weld materials in the creep range. Don't worry about it if your temperatures are not "up there". If you are very hot, then perhaps you should worry about both the circumferential AND longitudinal entries in CAESAR II - circ. is defined through SIF's & Tees and long. is defined below OD & wt through the Seam Welded check box.