Bridge expansion joints shall be installed and replaced
Based on the technical specifications and summarizing the construction experience for many years, this paper analyzes the technical key points of the construction of bridge expansion joint replacement in terms of the causes of bridge expansion joint diseases, the replacement process of expansion joint, the matters needing attention in construction and other aspects.

1. Causes of bridge expansion joints

Increases with the increase of traffic volume and vehicle load, bridge expansion joints due to set on the beam end tectonic weak positions, directly from the repeated impact of wheel load, and long exposure in nature, the environment is bad, because of material wear and fatigue, and the combination of concrete slab or beam intensity is not enough, is the most easily damaged bridge structure and difficult to repair parts.
The main reasons for damage of bridge deck expansion device can be summarized as follows:

1.1 construction reasons

Both sides of the telescopic device cement concrete and asphalt concrete pavement layer is not good combination, compaction is not dense, easy to produce cracking, falling off.
Coupled with rigid and flexible joint, easy to produce steps, and ultimately cause the failure of the telescopic device;
After pouring concrete (or other filler) pouring is not dense, often honeycomb, cavity, and so on, can not meet the design strength requirements, it is difficult to withstand the strong impact of vehicle load.
Sometimes, the traffic is opened ahead of schedule, which causes early damage to the anchorage concrete of itd, and thus reduces the operating environment of expansion joints.


1.2 poor maintenance and external influences

The original bridge pavement layer gradually aging, not timely and regular maintenance, so the damage continues to expand;
The sand soil and sundries falling into the telescopic device are not cleaned timely and carefully, which makes the original design of the telescopic amount can not be guaranteed;
With the increase of vehicle load and traffic volume, the impact of vehicle also increases obviously.
Bridge overload can not be effectively controlled, overload vehicles on the bridge on their own, the effective use of bridge telescopic devices and durability of a serious threat;

Bridge expansion joint replacement
Two, expansion joint replacement process

2.1 construction process

Construction plan preparation, construction machinery and tools preparation, excavation reserved groove, remove the original expansion device, cleaning groove, alignment positioning, embedded steel reinforcement (bolts), anchorage, installation of expansion device, cleaning reserved groove, backfill concrete.

2.2 construction technology

2.2.1 marking, cutting and concrete breaking
After the completion of traffic control, according to the actual middle line of expansion joint at the center of abutment (pier) in the operating area, the width required for construction will pop up from the center line of expansion joint to both sides according to the design requirements (the width is reserved according to different types of expansion joints), and attention should be paid to the change of abutment side width;
The spring line should be straight and of the same width.
Then the concrete seam cutting machine is used to cut the cement concrete pavement layer according to the drawn edges.
To ensure that the position of the slit, the size of accurate, vertical, straight, without defects.
Air compressor is used to remove and clean the cement concrete pavement layer at the expansion joints, gouge the concrete on the surface of the notch, and blow off the powder and slag with the air compressor pipe.
Then, other sundries clamped between the beam joints are cleaned to ensure the gap between the beam bodies.
Pay attention to take protective measures for the pavement layer outside the seam. It is strictly prohibited to eliminate and destroy the pavement layer to ensure the neat and straight edges and corners.
2.2.2 check, repair and implant embedded bars
After cleaning the debris between the groove and the beam, first check the good condition of the embedded tendon, such as the occurrence of bending deformation to straighten, make its position and form accurate.
If there is a lack, crushing or the height of the original embedded tendon is not enough after the bridge is lifted, the planting tendon shall be adopted. The planting tendon shall be carried out in accordance with the direction of the anchorage tendon of the expansion joint, so as to ensure a good stress and welding between the planting tendon and the anchorage tendon of the expansion joint.
When carrying out the construction of planting steel bars, the reliable technology of planting steel bars should be selected to ensure the quality of planting steel bars.
The adhesive shall meet the welding requirements, and the bearing capacity shall not decrease after welding, and the corresponding test report shall be provided.
Expansion device can be installed after meeting the design requirements.
Finally, the corroded part of the steel bar is cleaned with an iron brush.
Check whether the beam clearance meets the requirements. If not, it shall be processed to meet the requirements.
Check whether the embedded steel bar corresponds to the anchorage ring of the telescopic device, and adjust the anchorage ring if there are problems such as dislocation and phase twist.
In order to ensure the effective welding of steel rings and embedded parts, a certain number of steel plates with different specifications should be prepared as liners according to the actual joint size.
2.2.3 filling structural joints

Insert the corresponding thickness of foam plate into the structural crack, pay attention to have enough depth and tightness, above and groove bottom phase level.
Do not have loose and larger gaps to prevent leakage of slurry.

2.2.4 transport, storage and installation of expansion joints
According to the requirements of different models, lengths, types of sealing rubber parts and width of installation proposed in the design drawings, telescopic devices shall be purchased and assembled. Telescopic devices of different brands and models shall be supplied by complete sets of specialized manufacturers.
Telescopic device is assembled in the factory in advance. Before the assembly of telescopic device, the manufacturer shall determine the installation size according to the average temperature of the installation period and fix it with fixtures, so as to maintain the width of telescopic joint gap to meet the elongation and shortening caused by temperature change within the scope of norms.
When the telescopic device is transported to the site for storage, it shall be placed at least 10cm above the ground and covered with colored strip cloth to ensure that it is not damaged.
2.2.5 welding of expansion joints and anchorage bars
The welding time shall be carried out in a period of time suitable for the design temperature and within a day according to the set expansion gap width.
The supporting anchor rings and anchor bars on both sides of the telescopic device should be spot-welded successively along one end of the telescopic device. After spot-welding, the flatness, straightness, elevation and other items of the telescopic device should be comprehensively inspected before welding.
After the expansion joint is fixed, the elevation shall be re-tested to make sure that there is no deformation or deviation in the temporary fixing process. After that, the anchorage steel bar on the special-shaped steel beam and the embedded steel bar shall be welded firmly on both sides at the same time. It is better to weld it firmly at one time.
If there is any difficulty, one side can be firmly welded first. When the predetermined installation temperature is reached, the other side can be fully welded.
At the same time of welding, check the flatness of special-shaped steel beam with 3-meter straight ruler and plug ruler at any time.
Flatness is controlled between 0 and LMM to avoid jumping.
The number and configuration of welding personnel should be reasonable, and the welding time should be shortened as far as possible. After the completion of all welding procedures, fixtures should be removed in time, expansion joints and lifting joints devices should be removed, and a comprehensive quality inspection should be conducted after loosening. If the requirements are not met, adjustments should be made again.
Tie up the steel bar after welding.
2.2.6 concrete pouring and health maintenance
Cement concrete pouring is completed, and then covered with geotextile, strict sprinkling health, health period not less than 7 days.
No vehicles are allowed to pass through during the health maintenance period.
After health maintenance, cement concrete strength to reach more than 50% of the design strength, rubber sealing strip can be installed, before installation must be the joint as a template of foam board, fiber board, leakage of slurry concrete block all cut out clean, embedded in rubber strip.

Iii. Matters needing attention in construction

The installation of the telescopic device should be carried out after the bridge deck pavement is installed as far as possible. Before the installation of the telescopic device, the width, depth of the reserved groove and embedded steel bar (screw) must be checked to make it conform to the requirements of the installation of the telescopic device.
All dirt, dust and other unnecessary items in the groove must be removed.
When drilling and installing reinforcing bars (screws), the location of the original reinforcing bars must be verified, and the original reinforcing bars shall not be damaged. The placement location shall be adjusted according to the actual situation, and attention shall not be paid to damage the concrete at the edges when drilling.
Effective protective measures should be taken to prevent sundries from falling into the reserved cracks.


In short, in the process of bridge operation, telescopic joint device is the accessory to bear the maximum dynamic load. The small irregularity of bridge deck will make it bear a great impact force, which will easily cause the damage of telescopic joint.
Due to the damage of expansion joint device to a certain extent will cause the bridge deck jump, thus affecting the structural safety of the bridge.
Therefore, the expansion joint should be repaired in time to ensure that the expansion joint device is in a normal working state.