Please do a little search on axial restraints and you'll find plenty of info on this forum.
The maximum axial stress depends on the piping code you're working with. Different codes have different combinations for expansion stresses, so check the code you're working with to see the stress combination. Keep in mind though that even if the stresses are correct according to the code (deformation due to hot expansion stresses can be allowed) a displacement of 30-40 cm can occur in serious pipe damage. And there is an even more important thing to keep in mind.
You're saying that you have about 30-40cm displacement at the end of the line. That should result in very high axial forces. Can you make a support strong enough to withstand these forces?