Abstract: Apparatus is disclosed for protecting a structural object from the potentially harmful effects of a cyclic event such as an earthquake or high wind loads. A fluid spring is employed to stiffen the structural object and absorb kinetic energy stored by the spring. Fluid from the spring is exchanged with an accumulator where kinetic energy is dissipated as heat. A flow circuit regulates the exchange of fluid between the spring chamber and the accumulator chamber under controlled conditions to absorb the harmful effects of high external loads and to release the structural object when a high shock load is experienced.

Abstract: A damper is provided which includes a first cylinder containing a viscous fluid. The first cylinder is sealed at both ends by end plates. The first cylinder is adapted for connection to a structure such as a building or a bridge. A piston head within the first cylinder is adapted for reciprocation with respect to the first cylinder. A piston rod is connected to the piston head. The other end of the piston rod extends through the end plate and is adapted for connection to the structure. A second piston rod extends from the piston head through the second end plate. A first ring surrounds the piston head and is constructed from a material having a high coefficient of thermal expansion such as plastic. A second ring surrounds the first ring and is constructed from a material having a low coefficient of thermal expansion such as metal.