Using its experience in construction, Freyssinet has contributed to the development of advanced seismic devices that can be used alone or in combination to achieve the most efficient and suitable protection for a project. This protection is based on the three fundamental operational modes, namely: Isolation, Connection, and Dissipation.
The principle involves isolating the structure from the movement of the ground by using flexible connectors, mainly structural elastomeric bearings or sliding devices, to increase the natural period of the structure to protect it from, and reduce the response to, the seismic acceleration.
Seismic connectors have the characteristic of not only providing very low resistance to slow movements such as those due to temperature and stress-strain variations, but also providing a rigid link between the superstructure and its supports during rapid movements such as those caused by seismic events. Another advantage of connectors is the distribution of the major seismic horizontal forces between all the supports where installed.
Dissipation and Energy
The energy developed by earthquakes may be dissipated using dampers to reduce the effects on the protected structures. In the same way as the connectors, the dampers provide very low resistance to slow movements, but are completely efficient during rapid movements caused by seismic events. These dampers are generally used together with structural isolation bearings to reduce the movement of structures while limiting the forces to which they are subjected.
Freyssinet’s seismic capabilities are significantly enhanced by its close affiliation with Alga, a specialty manufacturer of bearings, expansion joints, post-tensioning and anti-seismic devices. Freyssinet owns 50% of Alga, and is the sole distributer in the United States and Canada for its products.
Further information about Freyssinet and Alga seismic products can be found in our brochures.