1. The current status of highway bridges in my country and the main reasons for their strengthening

1.1 Lack of accurate repair work

At present, the maintenance work in our country is imperfect and is often affected by environmental factors. In normal use of the bridge, the bridge deck is susceptible to damage due to the influence of different factors. Some maintenance personnel neglect the maintenance of the bridge, leading to uneven road surface, which causes cracks, material shedding or wear on the road surface. Especially the large-area grooves on the large bridge deck will cause the problem of jumping, which directly affects the safety of driving vehicles. In order to effectively solve this problem, in the construction process, we must pay attention to the maintenance of highway bridges. Nowadays, some small and medium-sized bridges lack normal maintenance, resulting in blockage of beam holes. If the construction is carried out on a rainy day, the bridge will definitely be affected and cannot be used normally if it is strongly washed by rain.

1.2 Incomplete maintenance and renovation work

Because the junction of the bridge pavement and the approach road surface was not filled with earth, uneven settlement occurred. In turn, it affects the stability and safety of the bridge, and it is very likely that the vehicle will jump when the vehicle is driving. The horse will greatly reduce the comfort of driving and affect the safety of driving. In addition, when using the bridge, if there is a lack of maintenance work, the bridge will also corrode over time, which will lead to the appearance of cracks. In the bridge maintenance, the key components and positions of the bridge are not maintained in time, causing problems with the components. Some construction workers only pay too much attention to widening the road surface and directly ignore the stability of the bridge during construction, which also increases the risk factor of vehicle driving.

2 Analysis of the importance of highway bridge processing

The service life of highway bridges is limited. Under the influence of operating environment, natural environment and other factors, highway bridges are damaged to varying degrees. Not only will it affect the safe use of the bridge and leave some hidden safety hazards, but when all the damage accumulates to a certain degree, it will definitely reduce the service life of the highway bridge and even threaten people's lives and property. Therefore, relevant departments must be aware of the importance of highway bridge strengthening construction.

First, save construction costs. When dismantling highway bridges with potential safety hazards, or in the process of rebuilding, the cost consumed is considerable. However, by strengthening the highway bridge, it can be restored to a stable operating state in time. The cost is less, which not only solves the problem of heavy traffic pressure, but also saves costs and obtains more social and economic benefits.

Second, achieve sustainable development. The processing of highway bridges not only meets the actual needs of the society, but also prevents damage to the environment and affects the subsequent development space, and fully reflects the sustainable development concept advocated by my country at this stage. The bridge strengthening and reconstruction technology integrates economic development, environmental protection and energy coordination into one, forming a brand-new sustainable development model. Its market development prospects are considerable, and it must be promoted.

3 Key points of highway bridge processing and construction technology

3.1 Superstructure processing and construction technology

(1) Strengthen the bridge section and strengthening. When the performance of the highway bridge is insufficient in all aspects, the method of increasing the cross section or increasing the strengthening can be adopted to expand the area of the side and bottom of the bridge, and continuously strengthen the rigidity, bearing capacity and safety of the bridge. By continuously improving the stability of the overall structural department, the bearing capacity of highway bridges is increased.

(2) Reinforce the bridge deck. In the case of bridge damage, the strengthening concrete can be laid flat on the bridge deck, and then the previous bridge deck can be gradually chipped away. A new bridge deck is paved on the basis of the previous bridge, and the strengthening process is closely integrated with the original bridge to form a new whole. Finally, the goal of improving the compressive strength of the main girder is achieved, and the load distribution of the bridge is improved at the same time, resulting in a continuous increase in the load-bearing capacity of the bridge, which can quickly adapt to the heavy traffic pressure.

(3) Use anchor shotcrete. At the spraying surface of the steel mesh of the expressway bridge, a layer of concrete material is evenly spread by using a high-speed spraying machine, and after all of it has solidified into a hard block, strengthening concrete can be formed. This method can not only strengthen the bearing capacity of the bridge, but also improve the integrity of the bridge structure and increase the load capacity of the bridge.

(4) Adopt the method of pasting steel plate to strengthen the concrete. On the basis of maintaining the original size and structure, the construction is carried out by using the technology of sticking steel plates to strengthen the concrete. The construction operation method is relatively simple, does not waste a lot of time, and the technology is guaranteed. This kind of concrete technology is mainly used to fix the steel plate on the tension surface and weak position of the concrete structure, so as to ensure the overall structure of the steel plate and the strengthening structure of the concrete. If you want to improve the bending strength of the bridge, you can paste the steel plate on the bottom of the bridge, and reasonably control the designed shear strength. If you want to increase the shear strength of the bridge, you can install steel plates on the side of the structure to ensure that it is consistent with the direction of the shear force of the original structural members. At the same time, when the steel plate is deformed forward, it is necessary to design the construction technology of steel plate sticking and strengthening concrete, so as not to reduce the quality of concrete and to ensure its integrity.

3.2 strengthening technology of substructure

(1) Increase the number of pile foundations. If the bearing capacity of the highway bridge pile foundation is relatively low or the buried depth of the foundation is too large, the method of expanding the foundation area at the bottom of the bridge can be used when the bridge is strengthened. Before strengthening, the strength of the bridge should be calculated accurately, while ensuring that the strength of the foundation meets the relevant requirements, especially the uneven settlement of each part of the bridge. If the bridge piers and abutments settle, it will directly affect the traffic safety of the bridge. Therefore, it is necessary to add bored piles near the original pile foundation, or inject an appropriate amount of strengthening concrete, to continuously improve the bearing capacity of the bridge.

(2) Increase the sheath. Generally speaking, the key to the phenomenon of cracks in the pier and abutment is that the burying depth of the foundation is comparable to that of the current, and the construction quality of the highway bridge is not up to standard, so the pier should be divided into three belts. In the case of the same width between the former residence and the side of the bridge pier, the width should be determined in accordance with the size of the crack in the pier and the degree of damage. The thickness of the shroud is controlled to about 15cm, and the outer surface of the pier is strengthening by adding a sheath. If the cracks in the pier are quite large and the damage is serious, a sheath must be added to the entire pier to ensure the normal opening of the bridge.

(3) Widen the bridge. When strengthening the lower structure of the expressway bridge, it is necessary to appropriately widen the original pier and abutment cover, and to frame the upper structure of the cantilever position. However, this method can only be used when the complete pier and the bearing capacity meet the relevant requirements. If there are conditions that do not meet the requirements, the foundation and piers of the highway bridge must be poured again.

For the disease problem of the highway bridge, after the damage is determined, the highway bridge must be strengthening. This can not only improve the quality of highway bridges, enhance their performance and extend their service life, but also ensure the safe driving of vehicles and reduce the occurrence of traffic accidents. Therefore, it is necessary to arrange professional technicians to regularly check the actual use of highway bridges. If problems are found in the road sections, they must be strengthening in time to avoid reducing their safety.