Elastomeric bearings and sliding devices
ALGASISM High Damping Rubber Bearings (HDRB):
The HDRB isolators are constituted of a series of vulcanized rubber layers separated by reinforcing steel plates, thus providing a device capable of supporting high vertical loads with minimal compression (elevated vertical stiffness) and allowing high horizontal displacements with relatively small reactions (low horizontal stiffness). The main property of the rubber is its ability to dissipate energy (damping capacity). When positioned underneath a building or underneath bridge beams, they have the effect of increasing the structure’s fundamental vibration period, thus greatly reducing any effects of seismic activity.
The HDRB isolators are bolted to external metal plates allowing them to be fixed to the adjacent structures using anchor brackets or bolts. The main advantages of this type of elastomeric seismic isolators are:
- More re-centering capacity after an earthquake.
- Lower stiffness to get a higher natural period.
- Increased damping (between 10 and 16%)
ALGASISM Lead Rubber Bearings (LRB):
These isolators are similar to the previous but with the exception that the dissipation of energy is obtained also through the use of one or more lead cores. Lead (used here at a level of 99.9% purity) has the property of undergoing plastic deformation as it dissipates energy and then re-crystallizing after a cycle of plastic deformation. Because of this, it is able to sustain an unlimited number of hysteresis loops. The main advantages of this type of elastomeric seismic isolators are:
- Higher initial stiffness. Thanks to the lead core these devices have rigid-plastic behavior. They therefore allow very small movement due to loads such as wind or braking.
- Higher values of damping (even greater than 30%).
ALGAPEND sliding devices:
ALGAPEND are Friction Pendulum Isolators resulting from the most advanced technology. Their main characteristics are the following:
- They allow the relative displacement of the structure in respect of the foundations following one or two spherical surfaces.
- The radius of the spherical surfaces determines the natural period of the structure.
- The natural period is independent from the mass of the structure therefore there is no torsion around the vertical axis during an earthquake since the center of mass and the center of stiffness are coincident.
- The friction coefficient of the sliding surface determines the equivalent friction damping of the isolation system.
- They are self-re-centering after a seismic event.
Download C X 9 _ Isoslab _ En _ v01.pdf