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Causes of bridge expansion joint disease

1 design reasons:

1. The beam end was not carefully considered in the design. Under repeated load, the beam end was damaged, resulting in the failure of the expansion device. In some bridge structures, the stiffness of the end of the bridge deck is insufficient. When the bridge deck is subjected to vehicle load, the repeated deformation of the bridge deck is too large due to the thin flange and weak transverse connection

2. The calculation of expansion and contraction is inaccurate, and the influence of the actual temperature on the expansion and contraction device during installation is not taken into account. The expansion and contraction device itself cannot or is difficult to adjust the initial displacement, and the type selection is improper. The use of too small expansion and contraction spacing leads to the damage of the expansion and contraction device

3. In some designs, the anchors of the expansion device are placed in the bridge deck pavement. There are few parts connected with the main beam (plate), and the force distribution is not easy to transfer. Small deformation may evolve into large displacement, eventually leading to the failure of the concrete bonding force

4. Using new expansion devices made of bonding or rubber materials, the selection of materials and structures is improper, and the waterproof and drainage facilities are imperfect, resulting in the corrosion of anchors and serious erosion of beam ends and bearings

5. The selection, mix proportion, compactness and strength of post cast concrete and pavement materials on both sides of the expansion device are not strictly specified in the design, resulting in varying degrees of damage, resulting in the decline of the operation quality of the expansion device

2 construction reasons

1. Insufficient attention was paid to the construction process of bridge expansion device, the construction process and standards were not strictly mastered, and the construction was carried out according to the installation procedures and relevant operation requirements, resulting in the failure of the expansion device to work normally

2. The cement concrete and asphalt concrete pavement layers on both sides of the expansion device are not well combined, and the compaction is not dense, which is easy to crack and fall off. Coupled with the rigid flexible connection, it is easy to produce steps, which eventually leads to the destruction of the telescopic device

3. The post cast concrete (or other filling materials) is not dense, and honeycombs and cavities often appear, which cannot meet the design strength requirements and is difficult to bear the strong impact of vehicle load. Sometimes the traffic is opened in advance, causing early damage to the anchor concrete in the transition section, resulting in the decline of the operating environment of the expansion joint

4. The installation of expansion device is one of the last processes of bridge construction. In order to catch up with the completion and opening to traffic, ignoring the internal quality management, some small installation teams without construction qualification are entrusted to carry out the construction. The construction personnel are careless, the anchoring reinforcement of expansion device is not welded firmly enough or the phenomenon of missing embedded reinforcement occurs, the spacing of expansion joints at the beam end is artificially enlarged and narrowed, and the position of positioning angle steel is incorrect, causing hidden dangers to the expansion joint itself, Quality cannot be guaranteed

3 poor maintenance and external influence

1. The original bridge pavement is gradually aging and cannot be repaired in time and often, so the damage continues to expand

2. The sand and sundries falling into the expansion device were not cleaned in time and carefully, so that the expansion amount of the original design could not be guaranteed

3. With the increase of vehicle load and traffic volume, the impact of vehicles will also increase significantly. The overload of the bridge can not be effectively controlled, and the overloaded vehicles go on the bridge by themselves, which poses a serious threat to the effective use and durability of the bridge expansion device

4, earthquake and other adverse weather conditions

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