1 The Necessity of Strengthening and Renovating Expressway Bridges

The service life of highway bridges has a certain period of time. Under environmental and human use factors, highway bridges will be damaged to varying degrees. This will not only prevent highway bridges from being used normally, but most importantly, they will be buried. The seeds of hidden safety hazards have been planted. Over time, damage to the limit will cause major problems in highway bridges, and even collapse, threatening the people’s property and lives. Therefore, it is necessary to strengthen and renovate highway bridges.

1.1 Strengthening highway bridges can save construction funds

If there is a problem with the highway bridge, the amount of demolition and reconstruction will be relatively large, the manpower and material resources will be consumed more, and the cost will be relatively high. Reinforce and transform the highway bridge to make it available for normal use, so the cost of repair will be relatively low, which can save a lot of time and resources. And if the highway bridge is demolished and reconstructed, it will cause an excessive burden on other roads, while strengthening and rebuilding the highway bridge can effectively avoid this situation.

1.2 Strengthening highway bridges can ensure bridge quality

Some unexposed and hidden quality problems can be discovered in the process of strengthening and rebuilding highway bridges, and then these problems can be solved in time to prevent safety accidents.

1.3 Strengthening highway bridges can promote sustainable development

If the highway bridge is rebuilt, the amount of engineering required will be relatively large, which will consume a lot of resources, and the construction will also cause damage to the surrounding environment, and the reinforcement and reconstruction of the highway bridge requires a relatively small amount of work and manpower and material resources. There are also few resources and little damage to the environment, which is in line with the concept of sustainable development in our country. Not only has the highway bridge been restored to use, but the environment has not been damaged, which is equivalent to protecting the environment in disguise. It is a very good way to serve multiple purposes.

2 Status Quo of Expressway Bridges and Reasons for Reinforcement

2.1 Lack of regular inspection and maintenance

When highway bridges are in use, there are few regular inspections. Then after the use time is too long, there will be some problems with the highway bridge. If there are potholes on the bridge deck, the vehicle will feel uncomfortable during driving, and it will also cause damage to the tires. Some materials of the fulcrum of the cantilever beam may fall off, which will cause large grooves on the bridge deck, leading to the occurrence of vehicle jumping. In addition, because the jump point is at the beam end of the highway bridge, not only the safety of driving cannot be guaranteed during severe vibration, but also the components of the motor vehicle will be damaged. Therefore, when expressway bridges are in operation, regular inspections and maintenance must be carried out to ensure the safety of expressway bridges and extend their operating life. According to the reference data, a considerable part of small and medium-sized bridges have not been maintained, and serious irregularities of the bridge deck and blockage of leaking holes have occurred, which poses great safety hazards and greatly reduces the service life. Moreover, sometimes some traffic accidents can cause great damage to expressway bridges. If they are not repaired, the aesthetic impact is small, and the safety accidents are large.

2.2 Lack of timely maintenance and renovation

During the operation of expressway bridges, there are places where the bridge deck and the road are bordered, and the uneven filling may cause vehicles to jump on or off the bridge. This will not only make drivers feel uncomfortable, but also cause loss to the bridge. Moreover, if the jumping phenomenon is serious, it is prone to major safety accidents. When highway bridges are in use, there are many cracks and potholes. In the daily inspection, no timely maintenance work is carried out, which will cause many small situations to gradually evolve into large hazards. In addition, the cone slopes, piers and abutments at the lower part of the bridge are often overlooked, and sometimes problems can not be found. And because these parts are often immersed in water, the erosion phenomenon is serious. If timely maintenance work is not carried out, it is easy to collapse. In addition, some departments have built bridges in factories and urban areas. Because there are a lot of industrial wastewater and domestic wastewater, it is easy to block the bridge holes. If timely repairs are not carried out, the bridges will be abandoned over time. 

3 Technical Points Of Highway Bridge Reinforcement Construction

3.1 Points to be paid attention to in superstructure reinforcement construction technology

3.1.1 Strengthen the strength of the bridge reinforcement Yao section

If the performance of the bridge is insufficient, you can choose to increase the cross-section and increase the reinforcement to increase the area of the bottom or side of the highway bridge. From the root to improve the stiffness and stability of highway bridges and the most important bearing capacity.

3.1.2 Reinforce the bridge deck

If the bridge deck is seriously damaged, another layer of reinforced concrete needs to be laid on the bridge deck when repairing. Then the previous bridge deck was removed, and a new bridge deck was replaced. Then rolling is carried out, so that the new bridge deck and the original bridge structure can be closely connected, so that the goal of improving the pressure resistance of the bridge main beam can be achieved. And it can further increase the bearing capacity of the bridge and prolong its service life.

3.1.3 Use anchor shotcrete

There is a layer of sprayed surface on the steel mesh of the expressway bridge. The concrete material can be sprayed by a machine that can spray at a high speed. After the surface is dry, it becomes a strong reinforced concrete. This spraying method can improve the bearing capacity of the bridge, and it can also improve the overall structure of the bridge.

3.1.4 Paste steel plate to strengthen concrete

If there is no need to change the size of the original bridge structure during the repair process, then you can choose to use the technology of sticking steel plates to strengthen the concrete. This construction method is not only less difficult to operate, but also takes a short time. The method of operation of this method is mainly to fix the steel plate tightly with adhesive at the weak point of the concrete structure, so that the stability of the entire bridge structure can have a higher guarantee. If you want to increase the bending strength of the bridge, you need to paste the steel plate to the bottom of the highway bridge; if you want to increase the shear strength of the highway bridge, you need to fix the steel plate on the side of the bridge structure.

3.2 Technical Requirements For Reinforcement Of Bridge Substructure

3.2.1 Expand the foundation area of the structure and increase the number of foundation piles

If the bearing capacity of the bridge is not enough or the bridge is buried too deep, the area of the foundation structure at the bottom of the mine bridge can be used for reinforcement and reconstruction. But if you want to adopt this method, you need to perform very accurate strength inspection calculations, and only the foundation strength can meet the calculation requirements. If the bottom pier and abutment of the expressway bridge subsidence, this time can be used.

3.2.2 Set the reinforced concrete

The cracking of the pier at the bottom of the bridge is basically because the depth of the foundation is not deep enough. At this time, the pier can be divided into three shrouds. The distance between the shrouds is the width of the side of the pier and the width of the shroud. Depending on the condition of the pier and abutment cracks, then the entire pier and abutment will be sheathed for reinforcement.

4 Concluding remarks

Generally speaking, the reinforcement and reconstruction technology of highway bridges is a difficult but very necessary work. It can not only increase the service time of the bridge, but also reduce the cost, reduce the waste of resources, and increase China's social and economic benefits.