When checking for local load stresses in nozzle/vessel junction using
WRC297, we model nozzle thru' WRC297 nozzle input pallete. This defines
flexible restraint at the defined nozzle junction. We can then export the
loads into 297 module to calculate the shear stress values for
circumferential & longitudinal planes in the vessel membranes & nozzle.

However, unlike WRC107, we do NOT get the stress summation for these
components. However, for all these components, we get 2 times the maximum
shear stress intensity values. Does this mean that these shear stress
intensity values at the 4 points on the membrane, have to be compared with
the yield stress value directly (per MAX. SHEAR STRESS THEORY) and not go
for stress summations? Also what about the Hoop stress value? OR should the
PRINCIPAL stresses be further computed manually ny summing up the [(hoop
stress + Long. stress*)/2] term to the sqrt[(long. stress*-hoop stress)/2 +
2* max shear stress intensity] and then compare this value with the yield
stress?

* considering that long. stress = axial stresses along the longitudinal
plane ???

Would appreciate if somebody can throw more light on this issue of code
compliance viz-a-viz WRC297 bulletin.

Nikhil,

FirstI would like to recommend that for the stress summation and the allowables please go through the paper titled "Criteria of the ASME Boiler and Pressure
Vessel Code for Design by Analysis in Sections III and VIII Division 2"Published by ASME in 1969.

Also the same thing ( minus the rationale for doing so) can be found in ASME SEC VIII Div 2 appendix 4.

There is nothing known as two times max. shear stress intensity. Shear intensity itself is defined as two times max. shear stress ( which is equal to the algebraic difference betweeen the max. and min. principal stresses).

Both WRC 107 and 297 tells you how to arrive at the membrane and bending stresses at the four locations based on the typical loadings as well as how to compute the shear stresses based on non dimensional graphs.

Next you compute the stress intensities by dividing every category ( general primary membrane, local primary membrane,primary bending ,secondary etc. as each one has different summation rules and allowables ) into normal and shear stress .

Allowable for bending is more in comparison to membrane as a result of limit analysis ( elastic-perfectly plastic i.e. with no strain hardening.)

All summations and allowbles will be as per DIV 2 requirements. There is no room for self imposed allowables.

Hope this answers your question.

A.BHATTACHARYA

STRESS ANALYST

BECHTEL CORPORATION