## 2 Literature Review  
### Retrofitting of Buildings  
Structural retrofitting can be divided into pre-earthquake retrofitting and post-earthquake retrofitting [11]. The objective of pre-earthquake retrofitting is to adopt retrofitting methods for a building whose structural bearing capacity does not meet appraisal requirements, so that the structural bearing capacity and other indexes meet such present requirements. A large part of the research studies, found through investigations, has been devoted to pre-earthquake retrofitting. For example, [PERSON] et al. [12] studied the mechanical behaviors of single-story brick masonry in-filled frames under the effect of lateral loads; [PERSON] et al. [13] investigated the effect of plaster on the performance of single-story single-bay masonry-infilled steel frames under in-plane base acceleration using a shake-table; and [PERSON] et al. [14] proposed a pre-earthquake retrofitting for a masonry typology widely used in social housing.  
Post-earthquake retrofitting is aimed at a structure damaged during an earthquake, but the performance point of the structure can still meet the immediate occupancy damage grade, through certain retrofitting methods. Along with the distress caused by an earthquake to people's lives and social development, structural retrofitting and repair have gradually gained the attention of seismic researchers and the construction industry [15; 16; 17; 18]. Structural repair and retrofitting are of great significance for extending the life of a building and ensuring the seismic capacity of the structure. The strengthening of buildings is a sustainable industry that can save construction resources and reduce project costs.  
After an earthquake, to protect lives and property, it is necessary to carry out post-earthquake repair work as soon as possible. The complete retrofitting of damaged buildings in a shorter period of time is an important concern for researchers. To shorten the evaluation time, some scholars [19] have used an affinity diagram to describe the seven common damage modes of structural walls, whereas others [11; 20] have proposed new retrofitting methods for saving valuable time in post-earthquake repairs. In addition to meeting the requirements for the strength and stiffness of components, post-earthquake retrofitting should also meet requirements regarding the unity of the strength and stiffness of the structure as a whole [21]. According to the actual situation of the project, the economy, practicality, and feasibility of the project should be comprehensively considered. [PERSON] [22], for example, proposed a combination of laboratory testing and numerical analysis based on using traditional and modern techniques to improve the durability and structural strength of materials. Traditional retrofitting processes have some problems such as the complexity of the professional systems, the tight construction schedule, the environmental restrictions of the construction site, the high requirements for construction quality and safety management, as well as the complex and changing site conditions [10]. Only relying on 2D drawings and planar training, it is difficult to meet the rapid retrofitting needs of modern post-earthquake buildings. Therefore, it is necessary to use BIM and AR technology to visualize retrofitting methods, so as to improve the level of intelligent management in construction processes.