Abstract: A device for positioning in a civil engineering structure at least one fixed point which, in normal time, locks a point of part of the structure in position relative to another, supporting, part which is considered fixed. In order to return the structure part to its initial position as soon as the disturbing action thereon ceases, the device (32) comprises at least two prestressed damping springs which are mounted in opposition either side of the fixed point and act, first, on the structure part which can move in relative manner, such as a bridge floor (10) and, second, on a structure part considered fixed, such as a bridge pier (11).

Abstract: A damper variably moderates movement of a piston on a rod in a cylinder filled with highly pressurized elastomeric gum. An axial bore through the piston allows relative ease of movement when a relatively low force is applied to a rod driving the cylinder. A high stress or acceleration on the rod forces a steel washer carried on the cylinder to deform and block the bore. The stiffness of the washer is proportioned to the ability of the clearance of the piston in the cylinder and the pressure and stiffness of the gum to establish a threshold. Damping is provided according to a preselected function, namely low initial resistance, and sharp increase is resistance to movement of the piston in response to stress exceeding the threshold. This function is suitable for damping in such applications as earthquake protection for structures and high stress protection for railroad beds.