Abstract: Device for use in building structures, particularly large cantilever type roof structures where net weight or variable external loads produce large deformations creating irregularities with respect to adjacent building elements, such as walls, large doors and drive-gates for hangars, workshops, etc., comprising one or more force applying devices (7) disposed between adjacent structural members for producing global displacement of the roof supporting members (2) to obviate the sum of local deformations at critical points of the structure, for example at the supporting rail (4) for drive-gates (5). Such displacement producing force applying devices can also be used for eliminating horizontal displacement of the supporting members.