Types and causes of bridge diseases?

It is very important to analyze the types and causes of bridge diseases. Only by knowing the types of diseases can we know the causes more clearly, and it is very important to deal with every detail. Zhong Da Consulting will explain the types and causes of bridge diseases for you.

Some diseases often occur in the process of bridge use. If these diseases are not maintained in time, the main structure will be destroyed. Therefore, it is necessary to strengthen the prevention of bridge diseases, analyze the causes of diseases, and then formulate corresponding maintenance countermeasures according to the characteristics of different diseases of bridges.

1 Types and causes of bridge deck diseases

According to the investigation of several bridge decks, the serious diseases of the bridge include loose and broken bridge deck pavement, repair damage, transverse cracks in beam and slab, holes in beam and slab bottom, tip-off at beam and slab bottom, water seepage and so on.

Due to the increase of heavy-duty and overloaded vehicles, the bridge deck pavement is seriously damaged, and the phenomenon of repeated repairs and losses has appeared. The damage of the connection between plates leads to the stress of single plate, and there are many bridges with transverse cracks in beam and slab. Many bridges have been replaced. After replacement, due to the lack of connection strength between the old and new decks, they will be damaged soon after replacement, which will seriously affect the safety of the bridge.

Analyzing the causes of the damage, most of them are that the pavement is flooded and the pavement is separated from the bridge deck. After flooding, the waterproof layer was damaged under the wheel load, resulting in water leakage on the bridge deck. After the asphalt pavement leaves the bridge deck, the damage accelerates quickly. After the rain, interlayer water cannot be discharged, and water vapor is formed in hot days. The bridge deck vibrates constantly under the action of automobile load, which accelerates the diffusion of water vapor and the destruction of pavement.

2 abutment disease types and causes

Abutment diseases are mainly abutment cracks and damaged wall behind the ear, and no other diseases such as uneven settlement, deformation and displacement are found. As shown in figure 1, statistics of bridge diseases can be found. As can be seen from Figure 1, bridge deck pavement damage and abutment cracks account for 55% of all diseases, and most of the reasons for bridge deck leakage are also related to pavement damage. Considering this factor, bridge deck diseases account for a larger proportion. Therefore, bridge deck and abutment diseases are the main problems.

The damage of pavement mainly lies in the material and thickness of pavement. For the same asphalt concrete pavement, the damage of 8 ClTI pavement is much more serious than that of 9 crn pavement. The investigation shows that the pavement thickness of the damaged parts is less than the design thickness, and some are abrasion losses, which are more caused by the camber of prestressed slab. It is also found that the elevation of individual bridge bearings is too thick, which leads to the elevation of the top of bearings rising, and the thickness of paving layer J decreases when the elevation of paving layer remains unchanged. The influence of materials is also obvious. The diseases of modified asphalt mastic mixture (sMA) pavement are less and lighter, and no damage is found on steel fiber concrete pavement. The external factor is the traffic volume, and the destructiveness of overloaded vehicles is certain, but the quantitative relationship between the values is not clear at present. According to the survey, the damage in the direction with more overloaded vehicles is obviously aggravated. The more overloaded vehicles, the more overloaded vehicles there will be. It is considered that hinge cracking and bridge deck fracture are directly related to overloaded vehicles.

Abutment cracks mainly occur in thin-walled abutment, and there is no cracking phenomenon in U-shaped abutment. Thin-walled abutment is related to abutment height, and the statistical results are classified according to abutment height (see Figure 2).

It is obvious from the survey results that the influence of abutment height is obvious. Thin-walled abutments above 5.5 m have cracks in different degrees (cracking reaches 100%), while pedestrian walkways and small bridges below 2.5 m have no cracks. Abutment above 5 m increases reinforcement and abutment thickness, and the effect is not obvious. It is considered that the calculation model of thin-walled abutment is no longer applicable when the stiffness of abutment is too large, and the stress can not be redistributed, which leads to excessive stress and counteracts the increased strength. It is not suitable to enlarge the cross section and reinforce the thin-walled abutment above 5 m.

3 Countermeasure analysis

In medium and small span bridges, the use of seamless bridges can avoid the occurrence of expansion joint diseases. For bridge deck pavement diseases, newly developed cold-rolled ribbed steel bars and steel fiber reinforced concrete materials can be used for protection. Compared with ordinary steel bars, cold-rolled ribbed steel bars have greatly improved design strength and strong bond strength with concrete. At the same time, the cold-rolled ribbed steel mesh has good overall stiffness and is not easy to deform, and local steel mesh collapse will not occur during bridge deck concrete construction. Using steel fiber reinforced concrete, a new high-strength composite material, to repair and strengthen the bridge deck can not only improve the crack resistance, wear resistance and durability of the bridge deck, but also prolong the service life of the bridge and reduce the maintenance. In addition, because of its high early strength, it can be opened to traffic in advance, which has obvious technical and economic benefits and social benefits and has good development prospects. For the crack problem, the disease can be prevented by improving the reinforcement ratio of the structure. For the abutment disease, the cracked bridge can be treated by "planting reinforcement" technology and coating epoxy resin and other protective layers on the concrete surface, and the overloaded vehicles should be strictly controlled. For the thin-walled abutment, the abutment height should be controlled.

4 conclusion

1) The functional damage of bridge deck pavement is mainly caused by water damage, poor combination of reinforced concrete and asphalt concrete, and poor drainage and waterproofing of bridge deck are the main reasons.

2) Heavy load and overloaded vehicles are the main causes of structural damage, and the design load should be appropriately increased while dealing with overload. Bridge deck maintenance should focus on reinforcement.

3) Cracks in thin-walled abutment are mainly related to abutment height. If the fill is too high, thin-walled abutment structure should be avoided. It is not economical to increase the cross section and reinforce the bar, and the effect is not ideal.

4) Repairing and strengthening the bridge deck with steel fiber reinforced concrete high-strength composite materials can not only improve the crack resistance, wear resistance and durability of the bridge deck, but also prolong the service life of the bridge and reduce maintenance.

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