How To Choose Between LRB And FPB Seismic Isolation Bearings?

With the increasing global adoption of seismic mitigation and isolation technologies in infrastructure projects, Lead Rubber Bearings (LRB) and Friction Pendulum Bearings (FPB) have become the two most widely used types of seismic isolation products. Many architects, engineers, and project procurement teams often have questions about the differences between these two systems. This article provides a multi-dimensional comparison covering working mechanisms, performance, cost, and application scenarios to help project owners make informed decisions.

• LRB (Lead Rubber Bearing) utilizes rubber deformation and energy dissipation. The rubber layers undergo shear deformation to extend the structural vibration period, while the lead core undergoes plastic deformation to dissipate seismic energy. The isolation period varies slightly with changes in building weight and vertical load.
• FPB (Friction Pendulum Bearing) uses spherical sliding friction and energy dissipation. The slider moves along a concave spherical surface, creating a pendulum-like motion that extends the vibration period. Energy is dissipated through friction during sliding. The isolation period is determined by the radius of curvature of the spherical surface and is independent of the building mass.

LRB bearings incorporate lead cores as energy-dissipating components.

FPB bearings are constructed with all-steel components and wear-resistant sliding materials, containing no lead elements. This makes them more suitable for environmentally regulated projects in regions such as Europe, North America, and the Middle East, where stricter sustainability and material standards may apply.

LRB bearings rely on the elastic recovery force of rubber for self-centering. After a major earthquake, a small amount of residual displacement may remain.

FPB bearings utilize the restoring force generated by the gravity load of the superstructure, allowing the slider to return toward its original position. Therefore, FPB systems generally provide stronger self-centering capability.

• LRB Lead Rubber Bearings are generally preferred for:

Multi-story public buildings and residential projects

Sites with relatively uniform geological conditions

Projects where engineers prioritize mature technology, extensive design experience, and well-established technical documentation

• FPB Friction Pendulum Bearings are generally preferred for:

Large-span and heavy-load structures

Buildings with significant variations in vertical loading

Overseas projects with strict environmental requirements

Projects requiring high standards for post-earthquake re-centering performance

1. For conventional small- and medium-sized projects, LRB bearings often offer advantages in overall cost efficiency.
2. For large-capacity and heavy-load applications, FPB bearings may provide better cost efficiency due to their higher load-carrying capability per unit size.
3. Both types of bearings are considered maintenance-free seismic isolation products under normal operating conditions and generally do not require routine maintenance after installation.

There is no universally superior seismic isolation product. The optimal selection should be based on a comprehensive evaluation of the project's seismic performance objectives, structural loading conditions, local geological characteristics, and environmental regulations in the target region.

For some projects, a combined solution using both LRB and FPB bearings may also be considered to achieve the best balance between performance, cost, and engineering requirements.