1. structural strengthening is directed against existing projects and is subject to objective conditions. it is aimed at strengthening the design and construction of specific existing conditions.

2. reinforcement works are often constructed on condition that no production is stopped or as few as possible to stop production, which requires fast construction speed and short construction period.

3. the construction site is narrow and congested, often restricted by production equipment, pipelines and original structures and components. Large construction machinery is difficult to play a role.

4. construction often has adverse effects on the original structure and components.

5. construction is often staged and staged, and it will also be interrupted due to various disturbances.

6., the workload of cleaning and demolition is often large, and the project is cumbersome and complex, and there are often many unsafe factors.

7. the design includes the checking calculation of the original structure and the calculation of the reinforcement structure design. It is required to consider the balance of the strength, stiffness and life of the new and old structures, and the coordination of the new and old structures.