Hello Fellow Stressers!!!

How to interpret the below statement for SSI (Sustained Stress Index) of Welding Tee (Sketch 2.1). I believe the SSI is equal to SIF?

The lower SSI (e.g.,0.75SIF) can only be used for Sketch 1.2 (Closely Spaced mitered bend) as per the statement below?

"(d) Where sustained stress or moment factors are required by the applicable Code (e.g., ASME B31.1, ASME B31.3), and in lieu of more applicable data, for components of Sketches 1.1, 1.3, 2.1, and
2.2, the directional sustained stress or moment multiplier can be taken as the component stress intensification factor. For all components of Sketch 1.2, the directional sustained stress or
moment multiplier can be conservatively taken as the smaller of (1) and either (2) or (3) below
(1) 0.75 times the applicable stress intensification factor
(2) (t/T) times the square root of the applicable stress intensification factor when t/T > 1
(3) the square root of the applicable stress intensification factor when t/T ≤ 1
The sustained stress or moment factors should always be used with the section modulus of the matching pipe and should not be less than 1.0."

Thanks in advance,

I believe if we have more applicable data, lower SSI (less than SIF) can be used. Is it by default, (e.g. 0.75SIF) can be used in lieu of more applicable data.

My undestanding:

1.For Sketches 1.1 through 1.3, and Sketch 3.1 through 5.1:
Use SSI = SIF

2.For Sketches 2.1 through 2.6:
Use SSI = min of (1)(2)(3)
(1) = 0.75 x applicable_SIF
(2) = (t/T) x sqrt(applicable_SIF) when t/T>1
(3) = sqrt(appplicable_SIF) when t/T<=1

The statement of General Note (d) of B31J should be reviewed again in my opinion

You can check the latest online help document version 13 for clearly understanding, section "Sustained Stress Index or Moment Factors (SSI)", it is saying:

"For tees and branch connections, CAESAR II uses a special B31J scaled value of SSI that depends on the ratio of branch to run thicknesses" --> means SSI=min(1)(2)(3) for sketches 2.1 through 2.6

"For bends, reducers, welds, and joints, the B31J applies the full SIF values for the SSI" --> means SSI=SIF for sketches 1.1 though 1.3, and 3.1 through 5.1