As per UKOOA specification, Shear stresses are ignored in the evaluation process of code stress. This is explicitly in mentioned in CAESAR II Technical reference manual 6-80. However, CAESAR II output reflects Torsional shear Stress. In what way, this torsional shear stresses are included in calcuating code stress. thiagarajan.murthi@paroman.com

As stated in the UKOOA specification, and in the CAESAR II technical reference manual, torsional stresses are not considered when calculating UKOOA code stresses. They are calculated and displayed simply for informational purposes.

In CAESAR II, UKOOA stresses are calculated as:

Code stress = Sab (f2/r) + (P Dm)/4t

Allowable stress = (f1 f2 LTHS)/2.0

Where:

Sab = axial bending stress due to mechanical loads

f2 = system factor of safety, usually 0.67

r = Sa(0:1) / Sa(2:1)

Sa(0:1) = long term axial tensile strength in absence of pressure load

Sa(2:1) = long term axial tensile strength under only pressure loading

P = design pressure

Dm = pipe mean diameter

t = pipe wall thickness

f1 = factor of safety for 97.5% lower confidence limit, usually 0.85

LTHS = long term hydrostatic strength (hoop stress allowable)

Thanks for your reply. However, in one of my Design Guideline which is an "Amendment to UKOOA" states that for bends, Torsional stresses are to be included while calculating effective axial bending stresses. The outlined empirical relation for calculating effective axial bending stresses is similar to the equation for calculating combined stress in BS 7159.
With this scenario,is there any method in CAESAR II, to include this optionally?

That seems like a UKOOA amendment that makes sense to me. Unfortunately there is currently no way that I can think of to perform the calculation in this manner in CAESAR II. Not that it's much consolation for you now, but we will look into providing this capability in the future.