The usual anti seismic design is based on the structural ductility that is the ability to undertake extensive plastic deformations which dissipate energy by hysteresis. In this kind of design large structural damages are allowed. Consequently, even if the structure collapse is prevented, expensive repairs are necessary after major earthquakes. No protection is guaranteed to the goods inside the structures.

However, for strategic structures, such as hospitals, power plants, control rooms, and primary bridges, the functionality after catastrophic events is a primary goal to be guaranteed in addition to the structural integrity.

The seismic isolation design, based on the concept of reducing the seismic energy transferred to structures, has proved to be the most effective design technology for protection against earthquakes; indeed not only the structure’s integrity is guaranteed but also the goods inside.

The whole isolation of a structure is obtained by placing adequate elastic supports in suitable positions in order to disentangle the ground from the structure allowing relative displacements.

The isolation principle is very simple: the idea is to shift the structure vibration period from low values (typically ranging from 0.3 to 1 seconds for a fixed base structure) where the ground acceleration is pronounced to longer periods (2-3 seconds) where the acceleration is highly reduced.

Additional acceleration reduction can be obtained by adding damping capacity to the isolators (energy dissipation).

E-Safe Antiseismic Elastomeric Devices

isolatori

AGOM antiseismic elastomeric devices, called E-Safe, are built to withstand vertical loads and simultaneous deformation in any direction, while allowing for minor rotations in any of the bearing’s axes.  They are inserted between the base of the structure and its foundations, in order to reduce acceleration to a target value so as to avoid structural damages and to keep the relative displacement between the ground and the structure to acceptable values. AGOM E-Safe seismic isolators  are generally characterized by high stiffness in case of small displacements, behaving like fixed points in order to prevent movements due to wind, etc., and by a low stiffness under large displacements in order to react and to absorb wide oscillations. After an earthquake the restorative properties of the rubber layers return the building to its original position.

The reference European Standard Code is EN15129.

HDRB

HDRB

Elastomeric seismic isolators type HDRB consist of multiple elastomer layers made of special dissipative rubber compound, separated by reinforcing steel plates vulcanized to the rubber layers and can be manufactured in rectangular or circular shape according to customer requirements. The horizontal loads are transferred from structures to bearings by means of steel bars or screws bolted to the external plates.

DWG

LRB

LRB

Elastomeric seismic isolators type LRB consist of a reinforced elastomeric bearing with one lead cylinder inserted in their core that provides very effective damping during extreme movements. The horizontal loads are transferred from structures to bearings by means of steel bars or screws bolted to the external plates.

DWG

H-Safe Antiseismic Hydraulic Devices

cilindri

AGOM antiseismic hydraulic devices, called H-Safe,  are basically composed by a cylinder filled by silicon fluid with a movable piston; controlling the fluid flow from one side of the piston to the other it is possible to obtain the required device response law. The hydraulic device response is governed by the velocity and it reacts to the imposed relative movement between its connection points that could be between structure and ground or between two internal nodes of a structure.  In general the device is connected to the structure by pins and spherical hinges to allow installation adjustments, structure service rotations and to avoid unwanted parasite bending effects of the piston.

The reference European Standard Code is EN15129.

VD

STU

Hydraulic seismic devices  type VD act as force control devices (VD = Viscous Damper): for slow motion, they give a negligible reaction, in case of fast motion they reaches the target force keeping the force level stable but allowing the movement to dissipate the energy imposed to the structure by the external excitation.  They allow to reduce the forces into the structure and to mitigate vibrations and accelerations by damping effect due to energy dissipation.

STU

STU

Hydraulic seismic devices type STU act as displacement control devices (STU = Shock Transmission Unit). The STU unit controls the displacement by stopping the fast movement increasing the reaction force up to the design value; this behavior allows to change the structure connection scheme from static to dynamic condition.