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What are the precautions for special bearings of highway bridges during construction

Source：www.jswanbao.com Release date： 2026-08-17

Special bearings include spherical bearings, bowl bearings, tension compression bearings, friction pendulum seismic isolation bearings, and shock-absorbing bearings. Compared with ordinary plate rubber bearings, they have higher precision requirements, complex structures, and strict protection requirements. Once installed, deviations can easily cause early damage, detachment, jamming, and loss of rotation/sliding function of the bearings.
1、 General requirements for pre construction preparation
1. Entry acceptance
Verify the model, bearing capacity, displacement, rotation angle, tensile strength, direction of movement (GD/DX/SX), production certificate, and inspection report; The key inspection for the friction pendulum support includes the friction surface coating, limit device, and reset structure.
Check the appearance of the support: the spherical surface and stainless steel sliding plate are free of scratches, rust, and bumps; The seal is intact; Temporary fixed connection plates and locking devices are complete.
It is strictly prohibited to cut or polish the steel components of the support body on site.
2. Storage and protection
The support pad must be elevated to prevent rain and sediment, and the stainless steel sliding surface and spherical pair must be covered with protective film;
The movable support comes with a temporary locking plate at the factory. It is strictly prohibited to remove it before installation and system conversion to prevent abnormal sliding and misalignment during the construction phase.
3. Measurement and laying out
Release the center coordinates, longitudinal and transverse axes, and elevation of the support; Curved bridges and skew bridges must be strictly laid out according to the design angle, and the supports cannot be forcibly adjusted.
2、 Construction of bearing pad stone (of utmost importance, with the vast majority of diseases originating from it)
1. The strength, geometric dimensions, and reinforcement of the cushion stone concrete must strictly comply with the drawings; The top surface of the cushion stone must be flat, avoiding local unevenness and tilting.
2. Elevation control accuracy: The elevation error of the top surface of the special support is generally required to be ≤± 2mm; the height difference of the four corners is strictly controlled to prevent the support from being biased and local stress concentration.
3. Choose one of the two treatment options for the top surface of the cushion stone:
Plan 1: Pre embedded steel plates for cushion stones, and grouting after leveling the steel plates;
Option 2: Use dry and hard cement mortar/special grouting material for the support to level it, and the thickness should not be too large to prevent cracking of the thick mortar layer in the later stage.
4. The top surface of the cushion stone should be cleaned and free of floating slurry and loose concrete; Grouting must be dense and there must be no voids.
Key point: Once the cushion stone of spherical bearings and friction pendulum bearings is uneven, single point pressure and rotation jamming may occur, causing damage in the short term.
3、 Key points for hoisting and positioning construction
1. The lifting points should follow the manufacturer's markings, and it is prohibited to directly tie the sliding surface, spherical surface, and sealing rubber parts; Single point oblique suspension is not allowed.
2. Slowly lower it when in place, and do not impact or drop it; After the support is in place, check:
center coordinates
Vertical and horizontal directions (one-way movable support DX distinguishes the sliding direction and cannot be installed in reverse)
Rotation direction and pre deviation of curved bridge support
3. Pre offset setting of activity support (high-frequency error prone point)
Continuous beams, steel box girders, and large-span bridges must be designed with pre deflection, taking into account the displacement caused by temperature shrinkage, prestress, and concrete creep after completion of the bridge;
If the pre bias is not set or the pre bias direction is reversed, the support will get stuck at the limit position after operation.
4、 Anchor and grouting construction
1. The anchor bolt holes of the support should be cleaned and kept moist without water accumulation; Anchor mortar/grouting material adopts non shrinkage high-strength grouting material.
2. The tightening force of the anchor bolts should be uniform, and they should be tightened diagonally in stages to prevent twisting and deformation of the support base;
3. During the grouting process, prevent the grout from flowing into the interior of the support, stainless steel sliding surface, and spherical friction pair; Once the slurry enters, it must be cleaned, otherwise it will directly cause sliding failure.
4. The upper beam can only be poured/erected after the grouting material reaches the design strength.
5、 Protection during the construction of the upper beam body
1. The formwork and support at the bottom of the beam shall not be squeezed or pressed against the side of the support; Unloading the bracket and lowering the beam should be synchronized and uniform. It is forbidden to suddenly drop the beam on one side to avoid the support being subjected to eccentric load and torsion.
2. When pouring concrete and prestressing, cover the support in a timely manner to prevent cement slurry from contaminating the sliding surface;
3. Welding operations should be kept away from supports, and sparks are prohibited from burning stainless steel skateboards and seals; It is strictly prohibited to weld on the support body.
6、 Removal of temporary locking device (critical process for system conversion)
1. The timing for removing the locking plate (temporary connection plate) shall strictly follow the design documents:
General requirements: After the completion of beam falling, bracket removal, prestressing and tensioning, and system conversion;
Early demolition can lead to uncontrolled slippage of the beam and displacement of the supports during the construction phase.
2. Inspection after dismantling: The support can rotate freely and there is no jamming in the direction of movement; Clean up metal debris and apply special silicone grease to the sliding surface (according to the manufacturer's requirements).
Friction pendulum bearings and spherical bearings can only use lubricating grease on their sliding surfaces, and ordinary butter is prohibited from use.
7、 Special precautions for different types of special bearings
1. Pot type rubber bearing GPZ
The rubber pressure plate shall not be exposed to direct sunlight or corroded by oil stains;
Pay attention to the integrity of the sealing ring to prevent sediment from entering the interior of the steel basin;
Be cautious in large angle working conditions and strictly control the installation angle.
2. Spherical steel support QZ/tension compression spherical support
Spherical pairs are strictly prohibited from being bumped or scratched, as even minor scratches can increase frictional resistance;
The anti pull connection structure of the tension and compression support should be installed in place, and the anchor bolts should not be missed;
The curved bridge ensures that the universal rotation is not constrained, and no improper limit should be added.
3. Friction pendulum seismic isolation bearing FPQZ

Remove the protective film on the concave spherical surface and sliding block friction surface until the system is converted;

Adequate sliding space should be reserved around the support, and piers, abutments, and blocks should not encroach on the range of motion of the support;

The built-in limit device and self resetting structure shall not be dismantled or cut at will.
4. Shock absorption, high damping, lead core isolation bearings
Avoid prolonged exposure of rubber components to sunlight, engine oil, and diesel fuel;
The installation should be kept level and not twisted. The initial state of rubber shear deformation must be regular.
8、 Construction of limit and seismic supporting structures
Many special supports are equipped with seismic blocks and lateral limit devices:
1. The limit clearance shall be strictly reserved according to the drawings, and if the clearance is too large, it will lose its seismic resistance; The gap is too small, and the normal temperature expansion and contraction will directly push the support to death.
2. A buffer gap should be reserved between the limit steel and the support, and it should not be directly tightened.

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