There are many ways to strengthen bridges, but they can basically be divided into two categories:

The first category is to change the structural system, adjust the internal force of the structure, and reduce the burden on the original beam.

For example: adding diagonal braces to reduce the span of the beam, changing the simply supported beam to a continuous structure, increasing the number of longitudinal beams, changing beam positions, and reducing the burden of the original beam by increasing the size of the newly built side beam and adjusting the lateral distribution coefficient.

The second category is to increase the cross-sectional size and strengthen the weak components with reinforcement.

There are many methods for strengthening weak components, which can be divided into two categories from the principle of action:

① Directly add tensile reinforcement materials in the tension zone, such as: repair welding rebar, paste steel plate, paste high-strength composite fiber (carbon fiber, aramid fiber), etc. The design of this reinforcement method must consider the phased force characteristics of the bridge reinforcement under load. The strength of the post-reinforcement material is limited by the deformation of the original beam, and generally cannot reach its tensile strength design value. Especially when it is reinforced by directly pasting high-strength composite fiber, the high-strength tensile performance of the composite fiber cannot fully play its role in the limit state at all. The "big horse-drawn cart" is a great waste. It is not safe to estimate the effect of post-reinforcement materials without considering the phased stress characteristics.

② The principle of pre-energization is adopted for reinforcement. Due to the effect of pre-loading, the stress state of the original beam is improved, and the load-bearing capacity and crack resistance of the original beam are improved. The use of pre-force reinforcement can give full play to the mechanical properties of the reinforcement material and improve the utilization efficiency of the material.

It should be pointed out that special attention should be paid to the design of the bridge reinforcement scheme: the maximum bearing capacity that the section can bear after the above-mentioned method of reinforcing the tension zone is strengthened under the premise of keeping the original beam section size unchanged. . The increase in bearing capacity depends on the reinforcement ratio of the original beam and has nothing to do with the reinforcement method used. In some cases, because the height of the original beam is relatively small and the reinforcement ratio is relatively large, the method of thickening the bridge deck can be used when the reinforcement of the tension zone alone cannot meet the design load requirements. At the same time, strengthening the compression zone of the beam and increasing the effective height of the beam can also achieve the purpose of improving the bearing capacity of the original beam. The usual practice is to take effective structural measures to strengthen the overall connection between the bridge deck paving layer and the original beam wing slab in combination with the maintenance of the bridge deck paving layer. Part of the bridge deck paving layer concrete can be considered in the joint work of the main girder.

In addition, the bridge reinforcement design should pay attention to the comprehensive utilization of various reinforcement methods by adjusting the internal force of the structure to reduce the burden of the original beam as much as possible to reduce the workload of reinforcement and reinforcement to a minimum.