In engineering, LRB generally refers to Lead Rubber Bearing, which combines lead core energy dissipation with rubber isolation to achieve the effects of "extending structural period, increasing damping, and dissipating seismic energy". It is widely used in lifeline and major projects such as buildings, bridges, and nuclear power facilities in high-intensity seismic zones. Occasionally, LRB may also refer to Liebherr's LRB series piling rigs (applied in foundation engineering). This translation focuses on the engineering applications of lead rubber bearings.
Core Principles and Advantages
An LRB consists of alternating layers of rubber and steel plates, with a lead core embedded in the center. The rubber provides vertical load-bearing capacity and horizontal flexibility; the steel plates restrict the lateral bulging of the rubber; and the lead core dissipates energy through plastic deformation during an earthquake. After the earthquake, the lead core can recover its shape and recrystallize, exhibiting a bilinear hysteretic behavior with a damping ratio of 15%–20%. It can isolate approximately 80% of seismic forces, significantly reducing the seismic response of structures.
- Key Advantages:Applicable to high-intensity (9-degree) and near-fault seismic zones; no additional dampers required; excellent post-earthquake reset capability; high durability and reliability.
Typical Engineering Application Scenarios
- Medical buildings in high-intensity seismic zones: For example, Chuantou Xichang Hospital (located in a 9-degree seismic zone) adopted 517 LRBs, making it the largest seismic isolated medical building in China and ensuring continuous functionality during earthquakes.
- Large transportation hubs: The terminal building of Beijing Daxing International Airport uses LRBs, with the lead core enabling a damping ratio of 18%. The horizontal displacement is controlled within 80% of the design value, enhancing seismic safety.
- Schools, emergency command centers, museums, etc.: LRBs installed in frame-structured teaching buildings can reduce the seismic base shear, protecting personnel and equipment.
- Near-fault bridges: For medium-to-long period (1.5–3s) isolated bridges in near-fault areas, although the strength of the lead core may decrease, the displacement remains controllable, making it suitable for strong earthquakes and complex seismic motions.
- Railway/rail transit bridges: LRBs applied in high-speed railway bridges reduce track deformation and train operation risks, meeting the long-period and high-deformation requirements of bridges.
- Cross-sea and special bridges: Combined with FPS (Friction Pendulum System) and other devices, LRBs control horizontal displacement and stress concentration, improving the seismic safety margin of structures.
- Nuclear power plants/small modular reactors: LRBs are used for seismic isolation of containment structures and main control room equipment, reducing horizontal acceleration response by 74.6% and concrete tensile stress by 33.5%. This prevents plastic damage and improves the seismic safety margin.
- LNG storage tanks, hydropower stations, etc.: Seismic isolation reduces the seismic response of equipment and structures, ensuring the safe operation of energy facilities.
- Retrofitting of old buildings: Adding LRBs between the foundation and the superstructure can improve the seismic performance of buildings in high-intensity zones without major modifications to the original structure.
- Prefabricated structures: LRBs are compatible with the rapid installation of precast components and address the seismic vulnerabilities of prefabricated structures, balancing construction efficiency and safety.