Lead Rubber Bearing with Great Vertical Stiffness & Restoring Capacity

Lead rubber bearing, short for LRB, is a kind of seismic isolation bearing that adds one or more lead cores inside a common natural rubber bearing and absorbs seismic energy by relying on the plastic deformation of lead cores.

LRB has a large vertical stiffness that allows it to support buildings stably; besides, it has a small horizontal stiffness that achieves the displacement of the bearing and offers a horizontal restoring force via the shear deformation of laminated rubber.

It can be used in the seismic isolation systems alone and adjust damping by regulating the diameter or number of lead cores to offer great design flexibility.

As an effective seismic isolation device, LRB is widely used in residential buildings, office buildings, teaching buildings, hospitals, town halls, museums, factories, etc.

Working Principle
Features
Category
Structure
Specification

Working Principle

Install a lead rubber bearing at the bottom or in the middle of the building to form a seismic layer and separate the upper structure from the lower foundation. When the earthquake occurs, the vibration energy of the lower foundation will be transferred to the lead rubber bearing first. When the LRB displaces horizontally, metal lead cores inside can not only provide a lateral resistance but also dispatch seismic energy through its deformation when large deformation occurs. In this way, the transmission of seismic energy to the superstructure can be effectively avoided or reduced, thereby ensuring the safety of the superstructure and personnel & devices inside and the normal operation of indoor equipment.

It demonstrates how lead rubber bearing works when the earthquake comes.

LRB can protect the safety of buildings and personnel and equipment inside.

Features

Lead cores with great energy dissipation capacity are provided to allow the LRB absorbing seismic energy through the plastic deformation.
Damping can be adjusted by regulating the diameter or number of lead cores to offer great design flexibility.
It has good horizontal deformation capacity and stable elastic restoring force, which allows the LRB maintaining excellent performance after repeated earthquakes and offering exceptional durability and reliability.
It has great vertical bearing capacity that can support buildings stably.
It prolongs the natural vibration period of the building, reduces the frequency of natural vibration and turns the violent shaking of the building into a slow movement.
The addition of lead increases the early stiffness of the LRB to prevent vibrations caused by storms.
It offers great seismic isolation effect and can effectively protect the safety of buildings and personnel & devices inside.
It offers exceptional durability, great fatigue resistance, hot air aging resistance, ozone aging resistance, acid resistance, water resistance and fire resistance, and its lifespan ranges from 60 to 80 years.
Easy to install, maintain and replace, no repair is required after the earthquake, bringing great social and economic benefits.
LRB can be used in seismic isolation systems alone, especially in engineering projects.

It demonstrates the relationship between shear displacement and shear force of the LRB.

The shear displacement hysteresis curve of the LRB reflects the deformation characteristics and energy consumption of the LRB in the process of repeated stress. The curve shape is full, indicating that the LRB has great plastic deformation capacity, good seismic isolation performance, excellent energy dissipation capacity, and amazing good stability.

Category

Lead rubber bearings are divided into round and rectangular lead rubber bearings by shape.

Round lead rubber bearing

Rectangular lead rubber bearing

Structure

Lead rubber bearing consists of a top and a bottom connecting steel plates, one or more lead cores, internal natural rubber layers, internal steel plates, a rubber cover and a top and a bottom sealing plates.

Internal natural rubber layer: Guarantee the horizontal displacement function of the LRB.
Internal steel plate layer: Provide a higher load bearing capacity that allows the LRB to support buildings stably.
Lead core: The purity of the lead core shall be at least 99.9%. When the LNB is subject to a shear deformation, it absorbs seismic energy through the plastic deformation. When the earthquake is over, lead core will restore the building to its original position automatically through the action of rubber shear force in the process of dynamic recovery and recrystallization.

Round lead rubber bearing structure

Rectangular lead rubber bearing structure

Specification

Table 1: Round Lead Rubber Bearing Specification (G4)
Item				LRB (G4)	LRB (G4)	LRB (G4)	LRB (G4)	LRB (G4)	LRB (G4)	LRB (G4)	LRB (G4)	LRB (G4)
Item				600-100	650-130	700-140	750-160	800-170	900-180	1000-200	1100-220	1200-240
Material property	Shear modulus (N/mm²)			0.39
Shape, dimension and dimensional accuracy of all parts	Rubber diameter (mm)			600	650	700	750	800	900	1000	1100	1200
	Lead core diameter (mm)			100	130	140	160	170	180	200	220	240
	Total rubber thickness (mm)			200	201.6	198	201.6	200	197.2	203	203	203
	1^st shape factor			37.5	38.7	38.9	39.1	40	38.8	35.7	39.3	42.9
	2^nd shape factor			3.0	3.2	3.5	3.7	4.0	4.6	4.9	5.4	5.9
	Connecting plate diameter (mm)			1000	1050	1100	1150	1200	1300	1400	1500	1500
	Connecting plate thickness (mm)			27	27	31	31	36	36	41	41	50
	Overall height (mm)			419.9	415.3	411.7	437.5	453.7	425.1	419.4	419.4	523.4
Vertical property	Vertical stiffness	K_v	(10³ kN/m)	1766	2102	2491	2817	3284	4128	4660	6042	7605
Vertical property	Datum level pressure (N/mm²)			6	6	8	8	10	12	15	15	15
Horizontal property	Initial stiffness K1	K_u	(10³ kN/m)	7.21	8.44	9.97	11.27	12.92	16.54	19.84	24,.1	28.57
	Secondary stiffness K2	K_d	(10³ kN/m)	0.554	0.649	0.767	0.867	0.994	1.273	1.526	1.847	2.198
	Equivalent stiffness	K_eq	(10³ kN/m)	0.87	1.17	1.39	1.66	1.90	2.30	2.76	3.34	3.97
	Designed nominal horizontal displacement (%)			100
Notes: Other specifications are available upon request.

Table 2: Round Lead Rubber Bearing Specification (G6)
Item				LRB (G6)	LRB (G6)	LRB (G6)	LRB (G6)	LRB (G6)	LRB (G6)	LRB (G6)	LRB (G6)	LRB (G6)
Item				600-100	650-130	700-140	750-160	800-170	900-180	1000-200	1100-220	1200-240
Material property	Shear modulus (N/mm²)			0.55
Shape, dimension and dimensional accuracy of all parts	Rubber diameter (mm)			600	650	700	750	800	900	1000	1100	1200
	Lead core diameter (mm)			100	130	140	160	170	180	200	220	240
	Total rubber thickness (mm)			200	201.6	198	201.6	200	197.2	203	203	203
	1^st shape factor			37.5	38.7	38.9	39.1	40	38.8	35.7	39.3	42.9
	2^nd shape factor			3.0	3.2	3.5	3.7	4	4.6	4.9	5.4	5.9
	Connecting plate diameter (mm)			1000	1050	1100	1150	1200	1300	1400	1500	1500
	Connecting plate thickness (mm)			27	27	31	31	36	36	41	41	50
	Overall height (mm)			419.9	415.3	411.7	437.5	453.7	425.1	419.4	419.4	523.4
Vertical property	Vertical stiffness	K_v	(10³ kN/m)	2259	2648	3077	3472	3940	5029	5994	7252	8631
Vertical property	Datum level pressure (N/mm²)			6	6	8	8	10	12	15	15	15
Horizontal property	Initial stiffness K1	K_u	(10³ kN/m)	9.83	11.30	13.34	14.96	17.16	22.14	26.56	32.13	38.24
	Secondary stiffness K2	K_d	(10³ kN/m)	0.756	0.869	1.026	1.150	1.320	1.703	2.043	2.472	2.942
	Equivalent stiffness	K_eq	(10³ kN/m)	1.03	1.33	1.58	1.86	2.12	2.62	3.14	3.80	4.52
	Designed nominal horizontal displacement (%)			100
Notes: Other specifications are available upon request.

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