1.1. General Requirements for Bearing Installation

Bearings should be properly installed on bearing pedestals, where the concrete strength grade must not be lower than C40. The height difference at the four corners of the pad stone top surface must not exceed 2mm. To facilitate properly installation, maintenance, and potential bearing replacement, the height of the pad stone must not be less than 100mm.

1.2. Reserved Holes for Anchor Bolts

Reserved holes for anchor bolts should be prefabricated at the bearing pedestal positions on the pier/abutment top surface. The diameter of the bolt holes should be 60mm to 80mm larger than that of the fixing components, and the depth of the bolt holes should be 60mm to 80mm greater than the length of the fixing components. The position deviation of the center and diagonal of the reserved anchor bolt holes must not exceed 10mm.

1.3. Inspection Prior to Bearing Installation

Checking the center mark at the exact center of the bearing's upper top surface. During properly installation, aligning it accurately with the X-axis (longitudinal) and Y-axis (transverse). The bearing elevation must comply with the design requirements.

Inspecting whether the bearing bolts and dust covers are securely fastened.

Verifying that the batch number corresponding to the bearing matches its specification.

Ensuring the surfaces of the bearing's upper and lower plates (which will be in contact with concrete or cement mortar) are free of dust and oil stains.

Checking that the pre-deflection value of the movable bearing matches the set value for the bearing at that location.

1.4. Installation by Gravity Grouting Method

Chisel the upper surface of the bearing pedestal to expose the coarse aggregate, forming a firm and irregular surface. Remove debris from the preformed holes and wet the top surface of the bearing pedestal with water. (When properly installing bearings via the gravity grouting method, the construction height of the pad stone should be 25mm lower than the original design height.)

Hoist the bearing onto the bearing pedestal, and adjust the bearing's height and flatness using leveling bolts, thin steel plates, or thin jacks.

Prior to sealing the bearing formwork, properly install a funnel at one end of the grouting pipe and insert the other end into the preformed hole. Under the action of gravity, pour non-shrink epoxy grout into the preformed hole through the funnel and grouting pipe, then quickly pull out the grouting pipe. (See Figure 1)

4)Upon completion of grouting into the preformed holes, immediately seal the formwork around the bearing. Insert the grouting pipe to the central position under the bearing, and grout from the center of the bearing to the surrounding area. During grouting, use a vibrator to compact the mortar and eliminate air bubbles, ensuring all gaps are fully filled with mortar. The mortar should be poured to a height 10mm above the bearing's lower base plate. (See Figure 2)

Prior to grouting, calculate the required volume of mortar. The actual amount of mortar used must not deviate significantly from the calculated value to prevent mortar shortage in the middle. Once the grouting material has set, remove the formwork and the steel blocks at the four corners. Inspect for mortar leakage; if necessary, repair the leaking areas and fill the gaps left by the removed steel blocks with mortar.

Do not subject the bearing to impact or perform any other operations above it until the epoxy mortar reaches the design strength.

Once removing the temporary side formwork, carefully inspect the surface of the non-shrink epoxy grout to make sure no cracks are present.

Once the epoxy mortar reaches the design strength, tighten the anchor bolts, promptly remove the bearing's temporary connection devices and temporary supports. Once confirming that all bearings are in normal working condition, properly install the bearing dust-proof devices.

5. Installation by Pressure Grouting Method

Pre-properly install grouting nozzles on the side of the bearing pedestal, leading to the interior of the preformed holes.

Inspect the top surface of the bearing pedestal to make sure its elevation meets the design level, is flat and smooth, and the height difference at the four corners does not exceed 2mm.

Apply a layer of epoxy mortar to the top surface of the pad stone. Once confirming the bearing's position and elevation, place the bearing in place. Once the bearing is correctly positioned, verify its location and elevation again, then pour non-shrink epoxy grout into the preformed holes through the grouting nozzles. The mortar should be filled until it overflows from the top surface to make sure full compaction. Once the mortar reaches the design strength, tighten the anchor bolts, promptly remove the bearing's temporary connection devices and temporary supports. Once confirming that all bearings are in normal working condition, properly install the bearing dust-proof devices. (See Figure 3)

1.6. Installation by Prefabricated Steel Plate Method

When the prefabricated steel plate method is used for properly installing bearings in cast-in-place beams: A lower embedded steel plate (with the lower sleeve adopting an upper sleeve structure) should be properly installed on the top surface of the pad stone. Reserved holes must only be prefabricated on the pier/abutment top surface, and no preformed holes are required at the bearing pedestal positions.

Chisel the upper surface of the bearing pedestal to expose the coarse aggregate, forming a firm and irregular surface. Remove debris from the preformed holes.

Install the formwork for the bearing pedestal, hoist the lower embedded components of the bearing onto the top surface of the pad stone's steel reinforcement mesh, fix the lower embedded components, and adjust their height and flatness.

Inspect the top surface of the bearing's lower embedded components to make sure their elevation meets the design level and the height difference at the four corners does not exceed 2mm.

Pour concrete for the bearing pedestal (the construction height of the pad stone should be 10mm higher than the original design height) and make sure the concrete covers the lower embedded steel plate by 10mm. (See Figure 4)

Once the concrete reaches the design strength, re-measure the elevation of the top surface of the bearing's lower embedded components using a level to make sure the bearing's position and elevation are correct.

Install the bearing on the top surface of the lower embedded steel plate. (See Figure 5)

Once the bearing is properly installed in place, promptly remove the bearing's temporary connection devices and temporary supports. Once confirming that all bearings are in normal working condition, properly install the bearing dust-proof devices.

1.7. Installation Specifications for Bearings in Concrete Structure Beams

(Including bearings at the beam bottom of precast beams with cast-in-place continuous middle cross beams)

First, pour concrete for the piers and bearing pedestals. Prefabricate preformed holes on the piers and bearing pedestals. Remove debris from the preformed holes and make sure the top surface of the bearing pedestal is flat, smooth, and the height difference at the four corners does not exceed 2mm.

Assemble the bearings in the factory, carefully level them, align the upper and lower components, and connect the bearing body into a single unit using temporary fixing plates (ensuring no loosening). Connect the bearing and the upper/lower embedded components (including upper embedded steel plates, upper/lower anchor rods, and upper/lower sleeves) into a single unit using anchor bolts. (Alternatively, the upper and lower embedded components may be transported in separate packages and connected into a single unit during bearing properly installation.)

Prior to on-site properly installation, inspect the connection status of the bearing and embedded components to make sure they are normal and not loosened arbitrarily. Check that the upper embedded steel plate surface is in close contact with the upper bearing plate, and verify the bearing's marks and properly installation direction to avoid incorrect properly installation.

Install the integrally connected bearing on the top surface of the pad stone. Once carefully verifying the bearing's position and elevation, pour high-strength non-shrink epoxy grout into the preformed holes using either the gravity grouting method (See Figure 1) or the pressure grouting method (See Figure 3). For cast-in-place beams, the prefabricated steel plate method may also be used for bearing properly installation.

Once the epoxy mortar reaches the design strength, reverify the bearing's center position and elevation, then tighten the upper and lower anchor bolts.

Clean the upper surface of the upper embedded steel plate, properly install the main beam formwork, and proceed with main beam concrete pouring and other related operations.

Once the on-site poured concrete reaches the design strength, remove the bearing's temporary connection devices and temporary supports. Once confirming that all bearings are in normal working condition, properly install the bearing dust-proof devices.

1.8. Installation Specifications for Bearings in Precast Beams

Pour concrete for the piers/abutments and bearing pedestals. Prefabricate preformed holes on the piers/abutments and bearing pedestals. Remove debris from the preformed holes and make sure the top surface of the bearing pedestal is flat, smooth, and the height difference at the four corners does not exceed 2mm.

Assemble the bearings in the factory, carefully level them, align the upper and lower components, and connect the bearing body into a single unit using temporary fixing plates (ensuring no loosening). Connect the bearing and the lower embedded components (including lower anchor rods and lower sleeves) into a single unit using lower anchor bolts. (Alternatively, the components may be transported in separate packages and connected into a single unit during bearing properly installation.) The upper embedded components (including upper embedded steel plates, upper anchor rods, and upper sleeves) should be transported in separate packages.

Prior to on-site properly installation, inspect the connection status of the bearing and embedded components to make sure they are normal and not loosened arbitrarily. Check the bearing's marks and properly installation direction to avoid incorrect properly installation.

8.4 Pre-properly install the upper embedded components (including upper embedded steel plates, upper sleeves, and upper anchor rods) at the bottom of the precast main beam. The flatness of the upper embedded steel plate surface must not exceed 1‰ of the maximum dimension of the steel plate. If a slope should be provided, adjust it using the embedded steel plate or beam leveling blocks to make sure the bottom surface of the embedded steel plate is horizontal during properly installation. (See Figure 6)

Install the integrally connected bearing on the top surface of the pad stone (See Figure 7). Hoist the precast beam to a position 20mm above the bearing top surface. Once carefully verifying the bearing's position and elevation, screw in the upper anchor bolts to position the beam. Pour high-strength non-shrink epoxy grout into the preformed holes using the pressure grouting method (See Figure 3).

If the gravity grouting method is used for bearing properly installation in precast beams: First, properly install jacks for beam jacking on the pier/abutment. (If there is no properly installation space on the pier/abutment, set up temporary rigid supports.) Hoist the precast beam (first properly install the bearing, equipped with lower sleeves and lower anchor rods, to the beam bottom using upper anchor bolts, and verify that the upper embedded steel plate is in close contact with the upper bearing plate). Place the precast beam on the temporary support jacks, adjust the beam's position and elevation via the jacks, then pour high-strength non-shrink epoxy grout into the gaps under the bearing and the preformed holes using the gravity grouting method (See Figure 1).

Once the epoxy mortar reaches the design strength, reverify the bearing's center position and elevation, tighten the upper and lower anchor bolts, remove the bearing's temporary connection devices and temporary supports. Once confirming that all bearings are in normal working condition, properly install the bearing dust-proof devices.

1.9. Installation Specifications for Bearings in Steel Structure Beams

When bearings are used for steel structure beams, the bearings should be connected to the steel beams using high-strength bolts, and to the piers/abutments using anchor bolts, sleeves, and anchor rods.

1) Preparation for Installation

Prior to erecting the steel beam, hoist the bearing and place it on the pre-properly installed bearing traversing slideway next to the bearing pedestal.

Mark the longitudinal and transverse centerlines on the top surface of the bearing pedestal, and re-measure the elevation of the bearing pedestal.

Inspect the surface of the bearing pedestal, chisel it to roughen the surface, and verify whether the position and depth of the preformed holes meet the requirements. If not, rectify immediately, then clean debris from the preformed holes.

2) Jack Arrangement

Arrange jacks at the positions directly below the center of each node at the bottom of the steel beam. These jacks will serve as the main supports for jacking the steel beam, ensuring uniform force distribution at all points.

Arrange one jack outside the center of each main truss node to adjust the balance of the steel beam during jacking.

Arrange one jack on the transverse side of the sliding seat (or temporary support point) at each left and right node to adjust the transverse position of the steel beam.

3) Adjustment of Steel Beam Plane Position

During the longitudinal traction of the steel beam, adjust its longitudinal position to within [specify tolerance, e.g., X] mm. Once erecting the four nodes, re-adjust the steel beam's plane position.

Jack up the jacks below the main nodes simultaneously, evenly, and slowly. Meanwhile, control the jacks below the nodes to stabilize and level the steel beam. Stop jacking when the sliding seat of the node is lifted 2cm off the surface. Adjust the elevation of the sliding seat top surface at each node to 2cm higher than the design elevation (considering the pre-camber), then place stainless steel plates and PTFE (polytetrafluoroethylene) sliding plates on the top surface of the sliding seat (apply lubricating oil between them).

Lower the jacks to allow the sliding seats (equipped with stainless steel plates and PTFE sliding plates) to bear the load, ensuring the jack tops are lifted off the surface. Based on the position of the four-node steel beam, and under the supervision of the survey team, jack up the jacks arranged on the transverse sides of the left and right node sliding seats to accurately adjust the steel beam's plane position. The plane position deviation should be controlled within 1cm.

4) Installation of Steel Beam Bearings

Traverse and position the bearing (placed next to the pad stone) using a chain block.

Hoist the bearing (with all components temporarily connected) using a chain block to make it closely contact the steel beam. Meanwhile, fill the gap under the bottom plate of the bearing with wooden boards to secure it.

Drive drift pins to align the bolt holes of the steel beam and the bearing, then tighten the high-strength bolts connecting the bearing and the steel beam.

Remove the wooden boards. Based on the pre-marked longitudinal and transverse centerlines on the bearing pedestal, accurately adjust the plane position of the bearing's lower base plate. Meanwhile, under the supervision of the survey team, adjust the elevation of the lower base plate according to the design or monitoring calculation requirements, and level the lower base plate to make sure the height difference at the four corners meets the code requirements.

Install the grouting formwork and perform gravity grouting on the preformed holes and the bottom of the lower bearing base plate (See Figure 1 and Figure 2). Once the grouted mortar reaches the design strength, remove the bearing's temporary connections, use jacks to lift the steel beam by approximately 5mm, remove the temporary support points (or sliding seats), and slowly lower the steel beam to transfer the load to the bearings, completing the load system conversion.

5) Adjustment of Steel Beam Elevation

If elevation adjustment should be provided: Temporarily connect the bearing into a single unit, loosen the connecting bolts between the bearing and the steel beam. Jack up the jacks below the nodes simultaneously, evenly, and slowly. Meanwhile, control the jacks below the nodes to stabilize and level the steel beam. Stop jacking when the gap between the node bottom and the bearing top reaches 2cm.

Under the supervision of the survey team, adjust the elevation of the height-adjusting steel plates or devices properly installed on the bearing top surface at each node according to the design elevation (considering the pre-camber). Then lower the jacks to allow the bearing and height-adjusting steel plates to jointly bear the load.

Remove the jacks to complete the bearing elevation adjustment.

Bearings should be inspected and maintained regularly during service, in compliance with the requirements of Clause 4.9 in JTG H11-2004 Code for Maintenance of Highway Bridges and Culverts.

Within three months after the project is completed and put into operation, inspect the bearings promptly to make sure they are in normal working condition and properly sealed.

Conduct another inspection procedure within one year of service. If any issues are found, identify the causes and rectify them immediately.

Conduct annual regular inspection procedures in the second and third years of service.

Once three years, the bearings will generally be in a stable working state. Subsequent inspection procedures may be conducted according to the actual situation, following the table below:

Table: Inspection, Evaluation, and Maintenance Instructions for Bridge Bearings

Prior to properly installation, carefully verify whether the bearing's specification, model, sliding type, and displacement match the design requirements specified in the bridge layout drawing. Simultaneously, inspect whether the bearing's temporary connection devices are loose and whether the bearing paint is damaged. Ensure all performance indicators of the bearing are in good condition.

Promptly after removing the bearing's temporary connection devices, seal the bolt holes with anti-corrosion grease. (Failure to do so will cause rusting inside the bolt holes, gradually corroding the paint anti-corrosion layer around the bolt holes, and ultimately damaging the bearing's anti-corrosion system, leading to overall rusting of the bearing.)

If flame cutting should be provided to remove the temporary connection devices, use flame-retardant materials to shield and protect the bearing body to prevent scorching. Avoid heating the steel body:

(1) Heat can cause the paint film to crack, directly damaging the bearing's anti-corrosion performance;

(2) High temperatures can alter the internal structure of the steel body, degrading its performance and potentially causing cracking or damage. If the bearing's paint surface is accidentally damaged, repair it immediately.

Once bearing properly installation, clean all exposed parts to prevent concrete splashes from contaminating the bearing body (which would impair its anti-corrosion performance). Touch up any paint scratches caused during construction with anti-rust paint and topcoat.

Prior to properly installing the bearing enclosure, carefully wipe the stainless steel sliding surface with cotton yarn to prevent dust or other debris from adhering to the wear-resistant plate surface. (Dust or debris on the wear-resistant plate surface may scratch the stainless steel surface, degrade bearing performance or even cause failure, and shorten the service life of the wear-resistant plate and stainless steel.)

Once properly installing the bearing enclosure, clean the bearing pedestal. Ensure the pad stone surface is flat, free of debris and standing water, and kept clean and dry.

Once bearing properly installation, cover the bearings to prevent rainwater infiltration until the beam's waterproofing measures are completed.