Please introduce in detail the construction process of laminated rubber bearings.

Please introduce in detail the construction process of laminated rubber bearings.

The construction process of laminated elastomeric bearings must strictly follow specifications to ensure positioning accuracy, uniform force distribution, and long-term performance. The following is a detailed explanation of the full process from construction preparation to acceptance, combined with China’s Code for Design of Building Isolation (GB 50011) and engineering practice experience:

I. Pre-construction Preparation Stage

1. Material and Equipment Inspection

Bearing Body Inspection

Verify the factory certificate and mechanical property test reports (such as vertical stiffness, horizontal shear modulus, ultimate bearing capacity), and sample for hardness testing (rubber hardness must meet design requirements, with an error ≤ ±5 Shore hardness).

Visual inspection: The rubber layer should have no bubbles or cracks, and the steel plate should be tightly bonded to the rubber without delamination (detectable by tapping; hollow sounds indicate rejection).

Auxiliary Material Inspection

Embedded parts (steel plates, bolts) need anti-corrosion coating detection (e.g., hot-dip galvanized layer thickness ≥ 85μm), and high-strength bolt torque coefficient testing (error ≤ ±10%).

Construction Equipment Preparation

Hoisting equipment (such as hydraulic jacks, cranes) must be calibrated for load capacity (≥ 1.5 times the bearing weight), a level (accuracy 0.1mm/m) and total station for positioning, and a torque wrench (accuracy ±3%) for bolt tightening.

2. Construction Plan Design and Site Survey

Plan Preparation

Clarify the installation sequence (such as symmetric installation from the structure center to the periphery) and temporary support plan (such as using steel pads for temporary load-bearing to avoid premature bearing stress), and draw detailed installation positioning diagrams (marked with bearing models, coordinate deviation ≤ 2mm).

Site Condition Confirmation

Foundation top surface flatness detection: Check with a 2m straightedge, height difference ≤ 3mm; embedded part position deviation ≤ 5mm (plane position), elevation deviation ≤ 2mm, and if exceeded, grind or repair weld for adjustment.

Ambient temperature control: The installation temperature should preferably be 5~30°C. Below 0°C, preheating measures (such as preheating the rubber bearing to above 10°C) are required to avoid rubber hardening and brittleness.

II. Core Process of Installation Construction

1. Installation and Positioning of Embedded Parts

Embedded Steel Plate Construction

Embed steel plates in the structure cap or beam according to the design drawings using the “positioning bracket + measurement verification” method:

Use a total station to lay out the central coordinates of the embedded steel plate, and weld positioning angle steel brackets to fix the plate;

Use a level to adjust the top surface levelness of the steel plate, with an error ≤ 1mm/m and plane inclination ≤ 0.2%;

Recheck the coordinates before pouring concrete, and avoid the vibrator directly contacting the steel plate during pouring to prevent displacement.

Bolt Embedding

For bolt-hole type bearings, embedded bolts must be perpendicular to the steel plate, with spacing deviation ≤ 2mm. The threaded part should be wrapped with tape for protection to prevent concrete contamination.

2. Bearing Hoisting and Positioning

Hoisting Key Points

Use special lifting tools (such as four-point lifting belts), with symmetrically arranged lifting points and a hoisting speed ≤ 0.5m/min to avoid rubber layer twisting caused by bearing shaking.

Pause when hoisting 20~30mm above the embedded steel plate, use a spirit level to adjust the bearing plane levelness (bubble offset ≤ 1 grid), and verticality deviation ≤ 0.5% (detectable with a plumb line).

Precision Positioning

The deviation between the bearing centerline and the embedded steel plate centerline ≤ 3mm. Steel wedge blocks can be used to temporarily fix the four corners, and slowly lower the girder after position adjustment to ensure full contact between the bearing and the steel plate (gap ≤ 0.3mm, checkable with a feeler gauge).

3. Fixed Connection and Removal of Temporary Supports

Bolt Connection

For bolt-connected bearings, tighten high-strength bolts 2~3 times in diagonal order. The initial tightening torque is 50% of the design value, and the final tightening torque must reach the standard value (e.g., M24 bolt final tightening torque is approximately 2200N·m), with anti-loosening marks.

Welding Fixing

For welded bearings, use intermittent welding (weld length ≥ 50mm, interval 100mm) with a weld height ≥ 8mm. Cool the rubber edges with a wet cloth during welding to prevent high-temperature damage (rubber surface temperature ≤ 60°C).

Removal of Temporary Supports

After the connection is fixed, gradually remove the temporary steel pads in the reverse order of installation to ensure uniform bearing force. Monitor the bearing compression during removal (deviation ≤ 10% of the design value).

III. Quality Control and Process Inspection

1. Installation Process Detection

Geometric Dimension Review

Force State Inspection

Monitor the initial vertical pressure of the bearing with a pressure sensor, which must conform to the design value (deviation ≤ 5%) to avoid local stress concentration caused by eccentric loading.

2. Functional Testing

Preloading Test

For important projects (such as hospitals, schools), perform 1.1 times the design load preloading after installation, hold the load for 24 hours, and measure the bearing compression and residual deformation (residual deformation ≤ 0.5mm) to verify the bearing’s elastic performance.

Initial Horizontal Stiffness Test

Apply horizontal force with a jack (≤ 5% of the design horizontal force) to test the initial horizontal stiffness of the bearing, with a deviation from the factory data ≤ 10% to ensure no installation anomalies.

IV. Protection and Sealing Treatment

1. Waterproof and Anti-corrosion Construction

Bearing Outer Wrapping Protection

Install a waterproof rubber sheath (thickness ≥ 5mm), fixed with stainless steel clamps (spacing ≤ 200mm). Fill the joint between the sheath and the structure with silicone sealant (depth ≥ 10mm) to prevent rainwater infiltration.

Embedded Part Anti-corrosion Enhancement

Reapply anti-corrosion paint at bolt connections (such as zinc-rich epoxy paint, dry film thickness ≥ 80μm), and coat the exposed steel plate surface with weather-resistant topcoat (such as acrylic polyurethane paint) to form a composite protective layer.

2. Drainage Structure Setting

Set a 2% slope drainage slope on the top surface of the structure around the bearing, and install a metal drainage trough (width ≥ 100mm) to ensure timely rainwater discharge and avoid long-term bearing immersion.

V. Acceptance and Safety Measures

1. Completion Acceptance Standards

Visual inspection: No damage to the rubber layer, no rust on the steel plate, and complete protective devices;

Performance testing: Sample 10% of the bearings for rechecking vertical bearing capacity (ultimate bearing capacity ≥ 2 times the design load) and horizontal displacement testing (good recovery performance under design displacement);

Data archiving: Including bearing certificates, installation records, test reports, etc., which must comply with the requirements of the Uniform Standard for Construction Quality Acceptance of Building Engineering (GB 50300).

2. Construction Safety Points

Set up a protective net for high-altitude operations, and operators must wear safety belts (with firm hanging points);

Set up a warning line in the hoisting operation area to prohibit non-construction personnel from entering;

Electrical equipment must have grounding protection, and fire extinguishers should be equipped during welding operations to prevent rubber combustion.

VI. Construction Adjustments for Special Scenarios

1. Installation of Large-tonnage Bearings

For bearings weighing > 50t, use a hydraulic synchronous jacking system (error ≤ 0.1mm) to lower the girder in stages to avoid over-limit single-point stress.

2. Construction in Complex Environments

Coastal areas: Add zinc anode blocks to embedded parts (sacrificial anode protection), and use salt spray-resistant coatings (such as PTFE) for bearing sheaths;

High-seismic areas: Reserve sufficient horizontal displacement space during installation (≥ 1.2 times the design displacement), and add temporary fixing limit devices to prevent bearing detachment under seismic conditions.

Summary

The core of laminated elastomeric bearing construction lies in “precise positioning, uniform force distribution, and comprehensive protection”. Every link, from embedded part precision control to bearing functional testing, must strictly follow specifications. Through whole-process quality control, the bearing can effectively play its isolation role during the service period. Construction precision directly affects structural safety and durability (e.g., each 1mm increase in installation deviation may shorten the bearing life by 5~8 years). It is recommended to carry out 1:1 on-site trial installation before construction to verify process feasibility before mass construction.

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