There are mainly 5 structural strengthening technology to strengthening bridges.

1) strengthening the weak components

For a weak component with serious defects on a bridge or a heavy vehicle that can not meet the safety bearing requirements, it usually takes a new material (shotcrete, concrete, steel plate, FRP wrap, steel or carbon fiber) to increase the cross section of the main beam or the main arch, and seal the cracks with high standard water mud mortar or epoxy cement mortar. Additional external post tensioned tendons should be added, external prestressing should be applied, or additional chemical components should be pasted with chemical binder.

2) add auxiliary components

When the bridge bearing capacity is insufficient or the bridge is damaged for a variety of reasons, new force components can be added to the original structure, such as the addition of longitudinal beams, beams or arch ribs, and the new prefabricated components can be replaced by the new prefabricated components that have serious defects and are not easy to repair. When replacing components, adequate temporary support must be provided and reliable technical measures should be taken to ensure the safety of the whole structure in construction.

3) change the structure system

The structure system mainly uses the continuous action of the beam or the beam, the combination of the plate and the combination of the arch beam to change the stress system of the structure, and improve the stress condition of the structure so as to improve the capacity of the bridge to bear the live load. If the simple beam is changed into a continuous beam, the hinge joint is changed to rigid connection, and the single span beam is transformed into a multi span structure with Auxiliary Pier and eight brace, and a layer of reinforced concrete slab is cast on the bridge deck of the arch bridge, and the arch system is converted into a beam type system.

4) reducing the constant load

Reducing the dead load of the upper structure of the original bridge can improve the stress condition of the original bridge and enhance the ability to bear the live load. Especially when the bearing capacity of the bridge foundation is limited, it can not meet the requirement of strengthening the upper structure and increasing the load bearing capacity of the live load. It is an economical and effective measure to reduce the constant load of the bridge to improve the ability to bear the live load. For example, if the solid belly arch bridge is converted into an empty arch bridge, the arch filler should be replaced.

5) reinforcement of pier and abutment and foundation

A considerable number of bridge defects and diseases are caused by abutment or foundation problems. This kind of bridge usually adopts reinforced concrete hoop, reinforced concrete pull rod and steel rod to apply external prestress, increase pile foundation and push method to reinforce bridge pier and abutment and foundation, improve the force condition of pier and foundation, and improve the bearing capacity of bridge.