Base isolators consist of a laminated rubber and steel bearing with steel flange plates for mounting to the structure. Ninety percent of our isolators have an energy dissipating lead core.
New construction or retrofits
For more than two and a half decades Dynamic Isolation
Systems has been helping architects, engineers, businesses
and institutions match the right earthquake protection technology to the specific needs and requirements of their individual structures.
The rubber in the isolator acts as a spring. It is very soft laterally but very
vertically. The high vertical stiffness is achieved by having thin layers of rubber
reinforced by steel shims. These two characteristics allow the isolator to move
laterally with relatively low stiffness yet carry significant axial load due to their high
vertical stiffness. The lead core provides damping by deforming plastically when the
isolator moves laterally in an earthquake.
Isolators from 12 to 60 inches in diameter with capacities of up to 4,000 tons are
manufactured. Custom dimensions are available for special applications.
The shims for isolators are cut to exacting tolerances by laser. The steel mounting
plates are machined by computer-
controlled milling machines that
give high production throughput
and accuracy. Molding each
bearing takes 8 to 48 hours
depending on the size of the
bearing. The curing phase is
continuously monitored to ensure
that the rubber is uniformly cured
throughout the bearing.
A sliding isolator consists of a PTFE (Teflon) disc that slides on a stainless steel plate. A slider may be manufactured with or without an elastomeric backing. The most common slider has the same construction as an isolator with a Teflon disc substituted for the flange plate.
Sliders support vertical loads and have low lateral resistance. They are typically used in conjunction with isolators and enable the designer to optimize the performance
of the isolation system. In some applications they are placed under lighter parts of the structure such as stairs and lightly-loaded columns. The elastomeric backing is
used to accommodate rotations in the structure. An added benefit of sliders is that they provide damping from sliding friction.
Sliding isolators have
been made from 12 to
41 inches in diameter.
Sliders are fabricated
with a Teflon disc that
mates with a stainless
steel sliding surface.
Steelwork and Fasteners
Dynamic Isolation Systems processes over 2,000 tons of steel a year. Steel mounting plates, sole plates, anchor bolts and fasteners are often fabricated
and supplied with
In addition to 112 isolators, DIS
supplied tapered sole plates,
masonry plates and all mounting
hardware for the I-40 bridge
over the Mississippi River in
Memphis, Tennessee (right).
DIS designs and builds bearings for non-seismic applications such as ship loaders. The purpose of the bearings is to control forces within the structure during the off-loading of oil from tankers.
San Rafael Bridge
DIS developed and fabricated bridge bearings with increased corrosion resistance for Caltrans.
The bearings are located six feet above the waterline and were fabricated with low permeability
rubber and stainless steel construction.
Viscous Wall Dampers
Dynamic Isolation Systems is the leader in seismic isolation with over 300 buildings and bridge projects completed worldwide. DIS now has damping technology that benefits taller, flexible structures. (Due to freight constraints, this product is only being offered in North America.)
The DIS Viscous Wall Damper (VWD) has been used extensively in Japan for more than
20 years in more than 100 projects. The DIS VWD uses
methods, details and materials that were developed in Japan. DIS is licensed to provide
this innovative technology in the United States. The first wall damper
project in the U.S. is a hospital in San Francisco, California.
Adding damping to a structure reduces the lateral displacements caused by earthquakes and wind by absorbing energy. When the lateral displacements are reduced, the
stresses in the superstructure are reduced by more than 50%. The reduction in structural cost more than offsets the cost of the VWDS.
The result is a better-performing
and more economical structure.
How Viscous Wall Dampers Work
Each VWD consists of a narrow steel tank connected to the lower floor, an inner steel plate
(vane) connected to the upper floor and a viscous fluid in the small gap between them.
During seismic excitation, the relative floor movement causes the vane to move through the viscous fluid. The damping force from the shearing action of the fluid is dependent on the displacement and velocity of the relative motion. Wall dampers are used to reduce the seismic accelerations and inter-story drifts by over 50% as well as to reduce wind-induced vibration.
Viscous Wall Dampers can also be constructed with 2 vanes. In the case of the double-vane damper there are 3 plates that form the tank. A double-vane VWD gives twice the damping force with only a small increase in plan size.
The viscous fluid used for wall dampers is a non-toxic, odorless, transparent fluid with a viscosity of 90,000 poise. The wall can be made to fit typical openings in the buildings. Dampers with widths of 6' to 20' and heights of 6' to 14' (with spacers) have been used in buildings. The force of the damper is proportional to the overall area between the vane and tank.
Buildings That Benefit From Viscous Wall Dampers
Flexible Medium To High-Rise Buildings
Buildings With High-Value Content
Buildings Requiring Continuous Operation
Viscous Wall Damper Testing
The first U.S. VWD project is a California hospital scheduled to be completed in 2012. As part of rigorous OSHPD review, prototype tests on 4 dampers were performed at UC San Diego's SRMD testing facility. The dampers were tested to a variety of displacements and velocities (sinusoidal and earthquake motions) in single and bi-directional conditions.
Over 100 cycles of seismic displacement tests demonstrated stable performance by the damper. Further, a 2,000-cycle wind displacement test per ASCE 7-05 was performed to confirm the adequacy of the damper for wind conditions. Some test results are presented here (right).
Cost Savings - Viscous Wall Dampers reduce the weight of structural steel and the total cost of the building.
Architectural Flexibility - The compact rectangular shape of the Viscous Wall Damper gives greater architectural freedom to the structure. The VWD is more easily accommodated than diagonal braces or dampers.
Better Performance - Viscous Wall Dampers provide superior seismic protection of the structure and its contents by reducing inter-story drift.
- Viscous Wall Dampers do not have seals and have no pressure under everyday conditions in a building. This avoids the possibility of leakage or the need to replace seals.
Viscous Wall Dampers are ideal for retrofits. They are easy to install and avoid the strengthening of beam column joints necessary with other types of damping solutions.
Low Mass Isolation
Dynamic Isolation Systems (DIS) is the leader in Seismic Isolation with over 300 building and bridge projects completed worldwide. DIS now has isolation technology that benefits lighter structures and equipment.
The DIS Low Mass Isolation System was developed in order to isolate computer floors in data centers. The system uses DIS Multidirectional Spring Units and roller supports. The spring stiffnesses range 2 to 50 pounds/inch, which are much softer than typical building and bridge isolator stiffnesses that are in the range of 5000 to 30,000 lbs/in.
The low spring stiffness allows isolation of lighter structures and equipment in the weight range of 1/2 ton to 50 tons.
Isolation reduces accelerations by more than a factor of 3, allowing equipment to remain operational during a major earthquake. The lower forces generated by isolation will result in reduced foundation costs.
How Does Low Mass Isolation Work?
The structure or equipment is mounted on a custom platform designed and manufactured by Dynamic Isolation Systems.
The system’s spring units provide lateral stiffness and hysteretic damping. The rollers provide vertical support and very low lateral resistance.
Each application is engineered for the ground motion at the specific project location. For installations within buildings, the accelerations at the level of the equipment need to be considered. As seen in these graphs, the ground accelerations are amplified up the building and modified by the structure’s response.
Testing and Performance
Over 200 shake table tests at DBE (Design Basis Earthquake) and MCE (Maximum Considered Earthquake) levels were performed on the DIS Low Mass Isolation System at the University of Nevada, Reno (UNR) and at the State University of New York at Buffalo (UB). These tests conclusively demonstrated superior seismic protection by reducing the accelerations while controlling displacements.
The first phase at UNR consisted of shake table testing and verification of the low mass isolation concept for various SAC motions with up to 3g input accelerations.
This was followed by rigorous testing and characterization of spring components along with shake table testing of the system at UB. The spring unit has the same properties in any horizontal direction, with a unique hysteresis loop, as shown in the graph below.
Only DIS offers a Low Mass Isolation System that provides true-engineered performance. For most applications, this means continued operation following an earthquake.
Hysteresis Loop for the multi-directional spring unit.
Forces and accelerations are reduced by more than a factor of
3 with the DIS system.
Foundations are minimized for structures such as self-contained data centers. In most cases, a simple slab is all that is required as the forces are reduced significantly.
High value equipment can be protected individually, which is more cost-effective than isolating the whole building.
Avoids business interruption expense.
Back up power systems and mirrored data storage are commonplace for data centers and essential equipment. The DIS Low Mass Isolation System fills the missing piece of the risk management puzzle.
Low Mass Isolation Candidates
Self-Contained Data Centers
Emergency Command Centers
Data Center Floors
Artwork, Including Statues
Dynamic Isolation Systems is the world leader in the seismic isolation of buildings. The superior protection that isolation provides can now be achieved within a conventional building with the DIS Floor Isolation System.
What are the components of the DIS Floor Isolation System?
The system consists of DIS multi-directional spring units and a combination of roller and slider bearings. A complete floor is assembled from modules connected by stringers. Standard computer floor tiles make up the top surface of the isolated floor.
The floor system is available in heights from 13 inches to 24 inches. The 24-inch height is a direct substitute for conventional-raised computer flooring.
Services and wiring run in the space beneath the stringers. Custom stringers are available to accommodate services, columns and geometric constraints.
When should floor isolation be considered?
Floor isolation is an ideal solution whenever seismic isolation of the entire building is not practical or economical. These include data centers, servers, medical equipment, high-tech manufacturing process equipment, artwork, and high-value products such as vaccines and medicines.
The DIS Floor Isolation System has been extensively tested using major earthquake motions.
Full-Scale Shake Table Testing
A full-scale portion of a DIS Floor Isolation System, comprised of two modules connected by stringers, was shake table tested at the University of Nevada, Reno.
More than 100 earthquake tests, including 75 DBE (Design Basis Earthquake) and MCE (Maximum Considered Earthquake) motions were performed.
This suite of tests was extreme with maximum accelerations of 6g and floor displacements relative to the shake table of 18 inches. The results showed good agreement with the performance predicted by nonlinear computer models. Peak accelerations and spectral accelerations were reduced by up to a factor of seven.
Seismic isolation features isolators under columns that are an integral part of the structure. The DIS Floor
Isolation System is installed inside a
building and is not a primary part
of the structure. The system is
an attractive alternative for
contents in cases where
it is not practical to isolate
the entire structure.
Shake Table Test Results from the University of Nevada, Reno
Selection of earthquake ground motions for the building analysis.
Development of floor acceleration spectral demands at the location in the building
which the floor isolation system will be installed.
Design and detailing of the floor isolation system to meet the required performance
Detailed design for manufacture and installation.
What design parameters should be considered?
Buildings are typically designed for the code-defined Design Base Earthquake (DBE). The same hazard level
is appropriate for design of the Floor Isolation System.
In cases of very high-value contents or equipment to be protected - or when continuous post-earthquake
operation is necessary - larger design earthquakes and maximum acceptable acceleration limits should also
be considered. Design earthquakes will be in the range of 6.0 to 8.0 on the Richter scale.
What is involved with structural modeling?
The response of a particular building and its contents to an earthquake is unique because the structure modifies and filters the earthquake input.
Factors that influence floor accelerations in a building include the structural type, the location within the building, the soil type and the proximity to faults. Due to the
uniqueness of these variables, specific design of a floor system is required. We will work with your engineer or can provide the service through our consultants.
A nonlinear time history analysis is used to model the floor system's performance. Our Floor Isolation System can be readily tailored to meet the exact design
Why is engineering required?
Demands on each floor in the building can be accurately determined only by proper analysis and engineer-
ing. For example, the accelerations in even a three-story building (right) may vary by a factor of three from
the ground to the third level.
Should earthquakes smaller than a DBE be considered?
Small earthquakes can be resisted simply by anchoring contents to the floors and walls. In addition, equipment such as computers are designed to accommodate accelerations caused by smaller earthquakes.
Should a Floor Isolation System be installed in a base isolated building?
No. A base isolated structure already provides superior content protection. Isolation of floors and buildings involves lengthening their natural shaking period. As both systems have similar frequencies, resonance between the two systems will generally give poorer performance than either on its own.
What are the installation considerations?
The DIS floor isolation system will typically displace from 8 to 24 inches horizontally depending on the severity of shaking. The floor system can be configured to be continuous to the walls of the room in which it is installed, in which case a closure assembly is provided around the perimeter of the floor. Alternately, the floor system can be detailed as a stand-alone unit with an edge closure. Adequate space is available beneath the floor to accommodate utilities and ductwork.
What was our first floor isolation project?
Dynamic Isolation Systems' first floor isolation project was the King County Emergency Center in Seattle. The floor system protects communications equipment and comprises a post-tensioned concrete floor isolated with lead rubber isolators and roller bearings. The new DIS Floor Isolation System is a lightweight solution that allows its application on any floor of a building.
What is unique about the DIS Floor Isolation System?
The DIS Floor Isolation System features a special multi-directional spring unit with a very low stiffness. This allows building contents which are relatively lightweight to be effectively isolated. The unique combination of sliders and roller supports, along with the multi-directional spring units, allows the system stiffness and damping properties to be tuned for each application.
LA SAC Motion 41 (2% in 50 yr)