What are the precautions for the construction of laminated rubber bearings in different environments?
The construction of laminated elastomeric bearings in different environments requires process adjustments based on environmental characteristics. The following details the construction considerations for typical scenarios such as climate, geology, and corrosive media, combined with engineering codes and practical experience:
I. Impact of Climatic Environments and Construction Key Points
1. Cold Regions (Ambient Temperature ≤ -10°C)
Material Selection
Rubber layers use neoprene or EPDM rubber (low-temperature resistance grade ≥ -40°C), and must pass the low-temperature brittleness test (no cracks at -25°C) before delivery.
Embedded steel parts adopt Q355ND grade (impact energy ≥ 34J at -20°C) to prevent low-temperature brittle fracture.
Construction Technology
The ambient temperature during installation must be ≥ 5°C. When below 0°C, preheat the bearing to 10~15°C with an electric heating blanket (control rubber surface temperature at 15~25°C) to avoid internal cracks caused by rubber hardening during hoisting.
Replace the hydraulic jack oil with L-HV low-temperature anti-wear hydraulic oil (pour point ≤ -30°C) to prevent equipment jamming at low temperatures.
Protection Measures
The outer sheath of the bearing uses silicone rubber (low-temperature resistance to -60°C), and the joints are sealed with low-temperature silicone sealant (curing temperature ≥ -15°C) to avoid sealing failure at low temperatures.
2. High-temperature and Humid Regions (Temperature ≥ 35°C, Humidity ≥ 80%)
Material Selection
Anti-aging agents (such as 4010NA) are added to the rubber layer, and the anti-aging grade must pass the 70°C×168h hot air aging test (hardness change ≤ +8 Shore A).
Embedded parts use 316L stainless steel (molybdenum content ≥ 2%) to prevent chloride ion corrosion.
Construction Technology
Avoid installation during midday high temperatures (prohibit construction from 10:00 to 16:00). Store rubber bearings in a shaded area (surface temperature ≤ 40°C) to prevent rubber softening due to direct sunlight.
Wrap the bearing edges with a wet cloth during welding (distance from the weld ≥ 100mm) to control the rubber surface temperature ≤ 60°C and prevent thermal aging.
Drainage and Moisture Protection
Arrange a circular drainage groove (depth ≥ 150mm) around the bearing, increase the foundation top slope to 3%, and open 5mm diameter drain holes at the bottom of embedded parts to prevent water accumulation.
3. Coastal and Salt Spray Environments (Chloride Ion Concentration ≥ 0.05%)
Anti-corrosion System
Embedded parts adopt a three-layer protection of “hot-dip galvanization (thickness ≥ 100μm) + zinc-rich epoxy paint (dry film thickness ≥ 100μm) + fluorocarbon topcoat (dry film thickness ≥ 80μm)”, and bolts use 8.8 grade stainless steel (A4-80).
The bearing sheath selects PTFE material (salt spray resistance grade ≥ 1000h), and the joints are sealed with chlorosulfonated polyethylene sealant (resistant to salt spray aging).
Construction Control
Wipe the surface of embedded parts with a special seawater cleaning agent (pH 7~8) before installation to remove salt crystals; use low-hydrogen electrodes (such as E4315) during welding to reduce weld porosity.
Monitoring and Maintenance
Conduct quarterly salt spray deposition detection after installation (standard ≤ 0.5mg/(cm²·d)), and rinse the bearing surface with high-pressure fresh water (pressure ≤ 0.3MPa) when exceeding the standard.
II. Adjustments for Geological and Load Environments
1. High Seismic Intensity Zones (≥ Grade 8)
Installation Precision
Control the plane position deviation ≤ 2mm (≤ 3mm in ordinary areas), and the top levelness error ≤ 0.5mm/m to ensure uniform horizontal displacement of the bearing during earthquakes and avoid eccentric loading.
Embedded bolts adopt double nuts for anti-loosening (with spring washers), and the gap between the bolt hole and bolt ≤ 1mm to reduce loosening under seismic impact.
Temporary Limitation
Add detachable steel limiting devices during installation (limiting gap is 1.2 times the design displacement), and remove them after the main structure construction is completed to prevent accidental displacement of the bearing during concrete pouring.
Performance Test
Sample 20% of the bearings for seismic simulation tests (such as 50 cycles of 10 times the design displacement), requiring residual deformation ≤ 0.3mm to verify their reset performance.
2. Heavy-load and Long-span Structures (Single Bearing Load ≥ 10000kN)
Hoisting Scheme
Adopt a hydraulic synchronous jacking system (control precision ± 0.05mm), load in three stages (50%→80%→100% design load), hold each stage for 1 hour, and monitor the bearing compression deviation ≤ 3%.
Stress Relief
Lay a 2mm thick brass shim (yield strength ≥ 140MPa) between the bearing and embedded steel plate to alleviate local stress concentration and prevent plate deformation.
Long-term Monitoring
Install vibrating wire pressure sensors (accuracy ± 0.5% FS) to real-time monitor the vertical pressure of the bearing, connect the data to the structural health monitoring system, and set the early warning threshold at ±15% of the design value.
III. Corrosive Environments with Special Media
1. Industrial Acid-base Environments (pH ≤ 4 or ≥ 10)
Protective Materials
The outer layer of the bearing uses fluororubber (resistant to pH 2~13), the inner side of the sheath is lined with a 2mm thick polypropylene plate (resistant to chemical corrosion), and embedded parts adopt nickel-based alloys (such as C-276).
Construction Taboos
Prohibit construction in rainy days or during medium leakage. Use a pH test paper to detect the site environment before installation (pH value should be within 6~8), and carry out environmental treatment first if exceeding the standard.
Sealing Treatment
All joints adopt double sealing of “polysulfide sealant + stainless steel baffle”, and the edge of the baffle is provided with a diversion groove to guide the corrosive liquid to the collection tank (volume ≥ 5m³).
2. Oil and Solvent Environments (Such as Garages, Chemical Workshops)
Isolation Measures
Set up a stainless steel oil baffle with a height ≥ 300mm around the bearing, coat the inner side of the baffle with an oil-repellent coating (contact angle ≥ 110°), and connect the bottom to an oil guide pipe (diameter ≥ 50mm) to the oil separation tank.
Material Selection
The rubber layer uses nitrile rubber (oil resistance grade ≥ IV), and must pass the motor oil immersion test (100°C×72h, volume change rate ≤ +15%).
IV. Complex Terrains and Special Scenarios
1. Plateau Areas (Altitude ≥ 3000m)
Construction Adjustments
Hoisting equipment must be equipped with a plateau-type engine (power correction coefficient ≥ 0.8), and the hydraulic system pressure needs to be increased by 15% to compensate for efficiency loss caused by reduced air pressure.
Store rubber bearings in a sealed package (filled with nitrogen inside, pressure ≥ 101kPa) to prevent expansion of internal bubbles in rubber due to low plateau air pressure.
2. Typhoon-prone Areas (Design Wind Speed ≥ 25m/s)
Temporary Fixing
Fix the bearing with guy wires during installation (≥ 4 wires per bearing), the included angle between the guy wire and the horizontal plane ≤ 45°, and the anchor point pull-out resistance ≥ 1.5 times the wind load.
Increase the embedded depth of embedded parts by 20% (e.g., anchorage length 5d in ordinary areas, 6d in typhoon areas), and add shear keys (section size ≥ 50mm×50mm).
V. Key Points of Environmental Adaptability Construction Acceptance
| Environment Type | Special Acceptance Indicators | Detection Method |
| Cold Regions | Horizontal stiffness variation rate ≤ 15% at -40°C | Low-temperature mechanical test |
| Coastal Areas | Anti-corrosion layer adhesion ≥ 5MPa after 1000h salt spray test | Cross-cut method + pull-off test |
| High Seismic Zones | Residual deformation ≤ 0.2mm after 50 cycles of 10 times design displacement | Quasi-static loading test |
| Acid-base Corrosion Areas | Rubber hardness change ≤ ±10 Shore A after 30d immersion in 10% sulfuric acid | Chemical immersion test |
Summary and Key Principles
The core of construction in different environments is “material adaptability priority, protective system enhancement, and dynamic process monitoring adjustment”. For example, the anti-corrosion grade in coastal areas needs to be increased by 1~2 levels, the rubber preheating temperature in cold regions must be strictly controlled, and the positioning precision in high seismic areas needs to be improved by 50%. It is recommended to carry out environmental simulation tests (such as salt spray chamber, high-low temperature chamber tests) before construction, and adjust the acceptance standards according to Appendix J of GB 50011-2010 Code for Seismic Design of Buildings to ensure the bearing service life ≥ 50 years in the target environment.
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