Earthquake Isolator

An earthquake isolator is a passive structural control element placed between a building’s foundation and superstructure with the aim of reducing the horizontal acceleration the structure experiences during an earthquake. It seeks to prevent damage to both the load-bearing system and non-structural components by reducing the seismic forces transmitted to the building.

Basic Principles of Seismic Isolation

The principle of seismic isolation is to increase the building’s natural period and dissipate seismic energy to enhance structural performance. The isolators absorb and dampen seismic waves before they reach the superstructure. As a result:

• The building’s oscillation period is extended,
• The acceleration experienced by the structure is reduced,
• The building and its internal elements are subjected to less stress.

As stated in the MEGEP module, isolation applications are particularly effective in short-period (rigid) structures. A period extension of typically 2–3 seconds is targeted.

Seismic Earthquake Isolator (Semra Orkan - Anadolu Agency)

Components of Seismic Isolation

Earthquake isolators consist of various components designed to provide flexibility not only in the horizontal direction but also in the vertical direction in some designs:

• Elastomeric rubber layers
• Steel plates
• Lead core (optional)
• Connection plates
• Energy dissipation components (hysteretic or viscous)

These components are optimized for both load-bearing capacity and energy absorption.

Types of Earthquake Isolators

Elastomeric Rubber Isolators

These isolators are made by bonding rubber and steel layers together, providing flexibility in the horizontal direction and stiffness in the vertical direction. They are commonly preferred due to their low maintenance requirements, long service life, and cost advantages.

Lead Rubber Bearing Isolators (LBRB)

In this type of isolator, a lead core embedded within the elastomeric structure provides energy dissipation through plastic deformation. According to sources, these isolators have energy dissipation capacities of 30–40 percent.

Friction Pendulum Bearing Isolators

These isolators move along a curved surface. Energy is dissipated through the swinging motion. They stand out for their high energy resistance and ability to be reused after seismic events.

Sliding Bearings

These isolators dissipate energy through sliding on low-friction surfaces. They can be designed according to the direction of seismic motion—for example, as unidirectional or bidirectional sliding types.

Seismic Earthquake Isolators (Mehmet Kara, Elif Küçük - Anadolu Agency)

Effects of Seismic Isolation on Structures

Structural Performance

• Reduces risks such as cracking and collapse in the load-bearing system by lowering seismic loads.
• Prevents increases in stress in reinforcement.

Non-Structural Components

• Mechanical and electrical systems and furnishings experience less damage.
• Ensures continued functionality of critical facilities such as hospitals and data centers after an earthquake.

Comfort and Continuity

• Perceived shaking within the building is reduced.
• Enables critical buildings such as hospitals and administrative offices to remain operational.

Application Areas and Examples

• Hospitals: Widely used in city hospitals in Türkiye (e.g., Istanbul Başakşehir Çam and Sakura City Hospital).
• Bridges: Friction pendulum isolators are particularly preferred in long-span viaducts and bridges.
• Historic Structures: Isolation systems are also applied in restoration projects to protect cultural heritage from seismic damage.
• Schools and Public Buildings: Under the MEGEP program, training-supported applications are implemented in schools and public buildings planned for seismic strengthening.

Adana City Hospital Earthquake Isolators (Abdullah Doğan - Anadolu Agency)

Design and Installation Principles

• Soil Characteristics: The feasibility of seismic isolation depends on soil stiffness. Performance may be reduced on very soft soils.
• Adjacent Buildings: Sufficient clearance must be provided to allow the isolated structure to move independently from neighboring buildings.
• Vertical Load Capacity: The isolator must safely support the building’s dead weight and permanent loads.
• Maintenance: Elastomeric systems require minimal maintenance; friction-based systems require periodic surface inspections.

Education and Standards

The MEGEP module published by the Ministry of National Education provides comprehensive educational content covering theoretical knowledge, application principles, and technical drawings related to earthquake isolators. Key topics covered in the training include:

• Introduction and drawings of isolators
• Installation stages of isolator systems
• Technical analysis examples
• Application safety and checklists

Earthquake isolator systems are a technology that offers high efficiency in minimizing earthquake damage from an engineering perspective and are increasingly common today, especially in hospitals and public buildings. With various types such as elastomeric, lead-core, and friction pendulum isolators, they can be adapted to different building types. Supported by educational modules and technical presentations, these systems are being implemented in Türkiye with growing momentum, both in new constructions and in the seismic strengthening of existing structures.