I am trying out to model a double axial restraint in a single pipe header. The restraints are placed after each other. So my model consists of a)single pipe element b) axial fix c) single pipe element with significant higher stiffnes d) axial fix e)single pipe element

It has no pratical implementation, i am only looking for validation.

Now my problem is that when ever I considered pressure only, no reaction forces are printed on the restraints, what should be the case. So I ques CII is considering the elongation due to pressure on pipe elements and the accompanied reaction forces on the supports (Bourdon effect), however it does not add pressure thrust on axial restaints.

Can anybody tell me if ths is correct?

Did you calculate by hand what is the theoretical elengation? Might be too small to register. Might have been even ignored intentionally.

Caesar II does not consider elongation due to pressure unless you select Bourdon in Environment->Special Execution Parameters.

The mid pipe element of the model (in between the two anchors) is significantly stiffer than the outer parts, so even with the Bourdon option switched on it does not generate any reaction loads on the anchors. However there should theoretically be a pressure load on the anchors due to the pressure thrust acting on the ends of the outer parts, unless this is assumed to be always in balance (this is usually the case in piping models)

There is no "pressure thrust" in a continuous system that goes out to external anchors. Introduce a discontinuity (such as a bellows expansion joint, or an open ended RV tailpipe) and you've got a different story.