Abstract: The present invention contemplates a rigidity control system for a variable rigidity structure incorporating variable rigidity elements, such as braces, for making the connecting condition with the frame variable between the locked and unlocked conditions for example, in which the vibration of a structure caused by external vibrational forces of an earthquake, wind or the like is attenuated by varying the rigidity of the structure. The rigidity control of the present invention imitates the tension and relaxation of a muscle in the self-balancing function of a living body. The vibrational condition of a frame is considered to be separately four conditions, i.e., the process of increasing the deformation in one direction, the process of decreasing the deformaton following thereafter, the process of increasing the deformation in the opposite direction and the process of decreasing the deformation following thereafter.

Abstract: A method of controlling a building against an earthquake according to the present invention comprises the steps of analyzing instantly the earthquake on the basis of data observed by earthquake sensors disposed in the building and narrow and wide regions, varying the connecting conditions in the building on the basis of obtained earthquake response forecast to vary the rigidity of the building or giving counter force to a building with an exciter to control oscillation according to individual earthquake characteristics.