Not sure which software you asked the question about. If it is related to STAAD.Pro here are a couple of suggestions. You can apply moment releases in supports through FIXED BUT MX MZ ...usually you would not release MY which represents the rotation about the vertical axis in STAAD.Pro.
Also seems like your supports can move in X by + or - 3 cm. Although there is no direct way to specify a support like that but you may consider modeling the supports as roller in X ( FIXED BUT FX ) and check the X displacements at these supports. If these are lesser than the 3 cm, I guess you can keep the roller. If the displacements are greater than 3 cm you may replace those with PINNED supports assuming that the movements are going to be restrained beyond 3 cm. Another way of handling this would be through defining multilinear springs but that would be more complicated.
I hope this offers some direction.
Sye, many thanks for your answer.
Sorry, I forgot to wirte the question is related to Staad.Pro and I dind't explain my problem properly.
The issue I have is that I am modeling a galery very long with 20 ºC of thermal load. This make than the last corvel of the galery has a high stress ratio due the horizontal forces caused by the thermal load (I tried without thermal loads and the corvel was right). The final part of the galery is supported by corvels and we modeled the support of the galery legs on the corvel with a bolted union with slotted holes that allow a dilatation of + or - 3 cm.
In the next screenshot you can see marked with blue circles the union with slotted holes and in green elipse the beam's corvel with high stress ratio:
If I model this nodes in Staad.Pro as fixed very high stress is generated on the beam, but if I let some dilatation in the nodes the thermal forces transmitted to the corbel will decress a lot.
I attach the "018-16-C07-R04.std" file and the "UPNHEA.upt" file for the composed profile UPN240+HEA160 I am using for the length of the beam marked with the green ellipse (I changed the upt extension to std for be able to upload the file, then you must return the extension to .upt for use the file):
Again, many thanks for your help!!!