Groin vault construction first exploited by the Romans, was used in Romanesque architecture and reached its ultimate expression in the Gothic architecture of the Middle Ages. Time however shows itself as structural weakness or overloading, dynamic vibrations, settlement, as well in-plane and out-of-plane deformations which can cause failure of masonry structures. Safety criteria must be specified by determining deformation limits between interacting parts of groin vault, to prevent emergency situation in heritage buildings. Safe exploitation of the building after crack appearance is possible, however cracked groin vault parts interaction must be specified by friction as well. The foundation settlement affect is the reason of shell part disintegration and hinge forming in main supporting ribs in the heritage’s vaulted structure. Three-dimensional scanning of arch structure by means of 3D laser scanners has been done and was used for geomet-ric modelling of masonry arch shell. The structures thrust line changes position in cross section and internal forces relocate significantly after the abutment deformations and crack forming in groin vaults. Hinge mechanism simulation between two rotating masonry parts has been performed and discussed at the present investigation. Crack propagation in arch cross section has been considered as the hinge rotation result. It defines the position of the thrust line and rotation point in cross section. Cyclic crack opening and contact between surfaces of masonry parts allow making assumption about the tensile stresses drop in interacting parts. Riga Dome Cathedral has a good example of groin vault in deformed condition which monitoring is esssential and which model has been created using improved rotation mechanism of masonry rib parts and cracks opening measurements. Deformed condi-tion vault model and long term crack monitoring will be used for analysis of the abutments deformations influence. Deformation criteria have been developed for safety exploitation of heritage masonry structures