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Shock transmitters create a very stiff restraint against a dynamic action, while permitting the slow movements of structures, for example those produced by thermal changes without opposing significant resistance. They are used when the structural behaviour should be different for service actions and seismic or dynamic actions. Experimental force-displacement curve of a shock transmitter obtained during high-speed testing. Preparation of tests on a shock transmitter for the Storebælt Bridge (Denmark). Installation of shock transmitters on the Stonecutters Bridge (Hong Kong, China).

EVED series elastomeric visco-elastic dampers consist of one or more layers of high-damping elastomeric mixture, characterized by equivalent viscous damping 15÷20% and shear deformation of 100%. Traditionally they are used as components of dissipative bracings in buildings in a framework; the layers of elastomer can be arranged both on the vertical and horizontal plane. Experimental hysteretic cycles of an EVED damper (frequency 0.5 Hz and shear deformation ± 100 %). Vibrating table tests on a concrete frame with EVED dampers on top of a reverse-V bracing. An EVED damper installed at the Gentile-Fermi school of Fabriano.

Guides are mechanical devices which permit sliding in one direction of the horizontal plane, transferring force in the orthogonal direction. Restraints are fixed mechanical devices which block displacements along a plane transferring horizontal force in every direction. Neither ones transfer vertical loads. Experimental force-displacement curve of a GU series guide. A guide for the bridges of the Panagia Grevena Section (Greece). A restraint for flyover 1.1 of the Caracas - Tuy Medio Railway (Venezuela).

They are divided into two categories: ELASTOMERIC Elastomeric isolators SI Elastomeric isolators with lead core LRB SLIDING Curved surface sliders FIP, FIP-D Flat surface sliders with dampersi VEL, VEP, VOP, VOTP, VELOP, VELOTP

They are divided into two macro-categories: NON-LINEAR Steel hysteretic dampers MEL, MEP, BRAD Elastic devices NE Shape-memory alloy devices SMAD LINEAR Elastomeric visco-elastic damper s EVED

They are divided into three categories: TEMPORARY Shock transmitters OT PERMANENT Guides and restraints GU, NET, FP, MCT MECHANICAL FUSE Mechanical fuse restraint devices SR

Steel hysteretic dampers exploit the plasticization of appropriately-shaped steel elements, designed to ensure a stable cyclic behaviour. Crescent-shaped and peg-shaped elements are the most used for bridges, while buckling-restrained axial dampers (BRAD) are the most used as dissipative bracings in buildings. For bridges, steel hysteretic dampers can be combined with shock transmitters. Experimental hysteretic cycles of a hysteretic damper with crescent-shaped elements. Steel hysteretic damper consisting of double-peg elements and shock transmitters (Jamuna Bridge, Bangladesh). BRAD dampers installed at the Cappuccini school of Ramacca (CT).

Series NE elastic devices (buffers) are anti-lifting axial devices consisting of a set of elastomeric disc inserted between steel plates. A set of bars connects the plates to the anchoring ends and allows the discs to operate under compression, despite the displacement direction. Elastic devices are traditionally used in bridges next to an abutment and/or between adjacent decks, over the joints. Experimental force-displacement curve of an elastic device. NE devices installed along the "Conexion Rosario-Victoria", in Argentina. NE devices installed in the Somplago flyover, the first seismically isolated European bridge (1974-1976).

They are divided into two categories: Fluid viscous dampers OP, OTP Spring fluid viscous dampers OVE, OVE*

Spring fluid viscous dampers are cylinder/piston assemblies characterized by a constitutive bond in which reaction force F depends both on speed v and on displacement x, according to law F=F0+Kx+Cvα, where F0 is pre-load force (if any), K is stiffness, C is the damping constant and α=0.15. Pre-load force can be useful to avoid displacements for horizontal service actions. Experimental hysteretic cycles of a spring fluid viscous damper without pre-load force. Spring fluid viscous dampers for the Badia Nuova flyover on highway A1. Spring fluid viscous dampers installed in Rio Higuamo Bridge (Dominican Republic).

The OP and OTP series fluid viscous dampers are cylinder/piston assemblies in which the lamination of a silicone fluid through an appropriate hydraulic circuit permits the dissipation of energy. The OTP series, unlike the OP series, permits thermal expansions without remarkable resistance. The typical resulting force-speed constitutive bond is not linear, i.e. F=Cvα, where F is force, C is the damping constant, v is speed, and α=0.15. Force-displacement cycles of a fluid viscous damper in an imposed displacement test with sinusoidal signal. Tests at FIP INDUSTRIALE laboratory on a fluid viscous dampers at Rion-Antirion Bridge (Greece). Fluid viscous dampers installed in the tuned mass damper at the skyscraper Taipei 101 (Taiwan).

Shape-memory alloy devices SMAD are axial restraining devices that exploit the superelastic properties of shape-memory alloys. The force-displacement curve, characterized by one or more "wedges" (sections where force remains nearly constant while displacement increases), allows SMAD to limit the maximum force transferred to the structure they are connected to. They are also characterized by a significant recentering capacity. Experimental force-displacement curve of a shape-memory alloy device. Vibrating table tests on brick walls with SMAD devices used as horizontal tie rods. SMAD devices installed at the San Francesco Basilica in Assisi.

SR series mechanical fuse restraint devices prevent relative movements between connected parts until reaching a force threshold. Upon exceeding such force, thanks to the break of a sacrificial element, they permit said movements. They are used to exclude the seismic protection system under operating conditions, allowing for free operation during design earthquake. Experimental force-displacement curve of a mechanical fuse restraint device. SR devices coupled with a bearing (Krka Bridge, Croatia). A device of the SR series installed together with fluid viscous dampers in Rion Antirion Bridge (Greece).