F&Q

Earthquake isolation, or seismic isolation, is a technology that helps protect buildings and their contents from the impacts of earthquakes. By adding specialized devices between the building’s foundation and superstructure, this system absorbs seismic forces, reducing the ground’s impact on the structure and minimizing damage.

Earthquake isolation uses flexible, lateral devices to lengthen the structure’s natural period. This adaptability absorbs seismic energy, minimizing the building’s movement and significantly reducing the destructive effects of horizontal shaking. Isolation also increases damping (absorption of energy), typically raising it from the usual 5% in standard buildings to 20% or more, which further lessens seismic impact.

Earthquake isolation safeguards both structural and non-structural components, allowing a building to withstand seismic forces with minimal or no damage. It is one of the most effective methods to ensure that a structure remains operational post-earthquake, thereby reducing the risk of downtime, repair costs, and loss of life. This approach is particularly advantageous for essential facilities that need to remain functional immediately after an earthquake.

Since an isolated building must move independently from the ground, connections for utilities like electricity, water, and gas require flexible designs that can accommodate multi-directional movement. Special connectors are commercially available to meet these demands.

Additionally, the perimeter of an isolated building needs an open gap to allow free movement during an earthquake, bridged by specially designed joints to maintain continuity.

Earthquake isolators alone are not typically effective against vertical seismic forces. However, additional damping systems can be implemented if vertical seismic resilience is required. Vertical forces generally exert less impact on both structural and non-structural elements than horizontal forces, so solutions are designed based on detailed structural analyses.

For effective isolation, the building’s design should integrate isolation from the beginning, including structural adjustments such as column sizing and layout. Square columns and beam-supported frames work better with isolation than long, narrow columns or unsupported slabs.

With earthquake isolation, structural calculations are performed using specialized software capable of modeling isolators and conducting both linear and non-linear analyses. Site-specific seismic data and building design goals are also factored into the analysis to ensure the building’s performance during seismic events.

Proper installation is crucial for isolation effectiveness. Specialized teams are typically required to precisely install each device to ensure functionality, as errors during assembly can be difficult to correct after installation.

While earthquake isolation does not directly reduce the need for foundational structural components, it may allow for smaller or fewer superstructure reinforcements depending on the building’s specific design. Any potential savings should be evaluated through structural calculations.

Yes, earthquake isolation can be applied to existing buildings to improve seismic resilience. A feasibility assessment by an expert is required to determine suitability for isolation retrofitting, followed by structural checks and static analysis.

Three primary types of isolators are used worldwide:

1. Friction Pendulum Isolators (FPB)
2. Lead Core Rubber Bearings (LRB)
3. High Damping Rubber Bearings (HDRB)

Each type has distinct properties suitable for varying load capacities, seismic zones, and building types.

Friction pendulum isolators offer unique advantages, including:

• High torsional stability.
• Compact design.
• Consistent performance over time, requiring minimal to no maintenance.
• High resistance to fire and other environmental factors.

In many regions, earthquake-isolated buildings are classified as “special constructions.” Design supervision involves independent review by certified experts to ensure seismic safety compliance. This process includes site-specific hazard analysis and supervision of both design and implementation stages.

Earthquake isolators have a long lifespan, often exceeding 100 years. Typically maintenance-free, they are designed with durable materials like stainless steel and Teflon to ensure longevity even under repetitive seismic events.

Most earthquake isolators are not damaged in seismic events and do not require replacement. These devices are built to remain functional throughout the building’s life.

While earthquake isolators generally do not require maintenance, periodic inspections are recommended to ensure ongoing functionality and to detect any signs of wear.

The size of earthquake isolators varies depending on factors like building weight, seismic zone, and architectural requirements. They can range from about 50 cm to 200 cm in diameter, customized for each project’s specifications.

For new constructions, earthquake isolation projects typically follow these stages:

1. Soil and Site Seismic Analysis
2. Architectural Planning with Isolation in Mind
3. Approval of Architecture and Static Calculations
4. Finalization of Insulator Design and Budgeting
5. Production, Testing, and Field Installation of Isolators
6. Completion of Superstructure Construction

Retrofit projects require similar steps, with additional considerations for existing structural elements and any adjustments needed to accommodate isolators.

Earthquake isolation may not be suitable for:

• Buildings adjacent to other structures unless all buildings are isolated.
• Sites with high liquefaction risk.
• Very tall or tower-like structures (12–13 floors or more), where additional damping systems are needed for stability.

There is no set price list for earthquake isolators, as each device is custom-designed based on building-specific factors. These include building weight, seismic intensity, and structural design requirements. Costs are typically estimated after preliminary calculations and analysis.