a system for the modification of the rigidity and damping properties of structural joints comprises at least an intermediate structure to receive , on both sides , two structures to be coupled ; releasable blocking means to immobilize , in a coupled condition , said two structures to be coupled and said intermediate structure ; first and second sets of bistable components , the structural resistance features of the components of the first set being different from those of the second set ; the components of the first set being internally connected to one of said structures to be coupled and to said intermediate structure ; the components of the second set being internally connected to one and other of said structures to be coupled ; said bistable components being in an unstable condition when all the mentioned structures are coupled together . the invention is applicable to the field of space vehicles .