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Seismic protection


Seismic protection of structures

The seismic protection of the structures is one of the most attractive goals of the structural engineers in order to save lives and minimize damages to structures in case of earthquakes of high intensity.

The absence of damage is of primary importance for some types of structures, such as:

• structures which house high risk components and materials (nuclear facilities, some chemical plants, etc.);

• important bridges and viaducts;

• important public buildings (hospitals, emergency control centres, energy and communication distribution centres, etc.);

• structures which are important for the national defence;

• structures which house costly components and electronic equipment;

• museums and historic and artistic monuments.

Freyssinet Products Company Italia technical dept. designs the devices and can cooperate with the structural designers in order to provide the best seismic protection systems.

Freyssinet Products Company Italia has developed a wide range of devices for the seismic protection of the structures, mainly divided in two categories:

Isolators

They have 3 main purposes: bear the weight of the structures, reduce the period of the structures and consequently the seismic action, dissipate energy

HDRB - High Damping Rubber Bearings

LRB - Lead Rubber Bearings

PS - Sliding pendulum system

PND/PNUD - Hysteretic Isolators with pot bearings

CSD/CSUD - Hysteretic isolators with spherical bearing

Dampers

Their main purpose is to dissipate seismic energy, in conjunction with or even without the use of isolators

Hysteretic Dampers

Elastic Dampers

Viscous Dampers

Visco-Elastic Dampers

STU - Shock Transmission Units

Hysteretic bracing systems

Base isolation for the buildings

Base isolation is becoming more and more a widespread technique to protect structures from the devastating effects of earthquakes.

How much can be useful to adopt this solution for seismic isolation?

One of the leading causes of death of people during an earthquake is the collapse of houses and other buildings. The design of a building carried out by the latest earthquake standards, leads to design the structural elements so that they can resist earthquake without collapsing, even if few damages can occur.

This approach, however, does not care about the non-structural elements (floors, curtain walls, windows) or the content of the structure (equipment, furnishings, furniture). What is then to have a hospital after an earthquake still standing but with the high-tech equipment destroyed, floors and curtain walls cracked? The costs of stopping the activity (just when the seismic event would require) and repair after an earthquake are considerable. The seismic isolation technique isolates the structure from the earthquake preventing its devastating energy to penetrate inside.

In this way the structure can be lightened, with considerable savings and, in case of earthquake, all content and non-structural parts are safeguarded. The damages after the earthquake will be so non-existent or marginal and the structure functionality is guaranteed.

But how much does it cost?

It is incredibly cheap, around 1 to 2% of the cost of the structure, far less than it can be the structural damage or business interruption in the event of an earthquake. Do not forget that often the cost of seismic isolators is lower than the structural savings that can be achieved through this technology, so that the cost of seismic isolation can be even negative.

The technology exists to protect against earthquakes and is well tested, it does not cost much and is affordable for everyone. Italy has become one of the world's most advanced standards for the design of structures subjected to seismic risk. Alga is a leading company in this field since many years, our technicians are available to perform linear and non linear analysis to proof how much can be easier to design structures using the base isolation technology.
   

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