In many cases, not only the structure which actually is modeled deforms due to the changes in temperature, but also the surroundings (which are approximated by constraints) will deform. You can take this effect into account by adding a Thermal Expansion subnode to the constraints. The constraints will then provide an extra displacement based on a given temperature field. For thermal strains, which have a simple variation in space (for example linear temperature variations), it is possible to completely offset the constraint stresses using this method. For more general cases, the stresses caused by the constraint can be significantly reduced.