## 1 Introduction  
Between 2000 and 2019, there were 552 earthquake events in the world. Earthquakes affected a total of over 1.18 billion people, led to approximately $636 billion in economic losses worldwide [1]. More than 95% of the total casualties after the earthquake were caused by the collapse of buildings. The destruction and collapse of buildings and various engineering facilities caused by the earthquake caused huge losses to the country and brought many inconveniences to people's lives. To ensure safety and improve the daily lives of people in the stricken area, post-earthquake inspections, evaluations, appraisals, and retrofitting of buildings should be conducted within an appropriate time [2]. Post-earthquake retrofitting refers to the seismic repair of a structure that has not lost much of its seismic resilience (or that still has a certain level of seismic resilience after being damaged by seismic force) and aims to restore its seismic capacity to a certain level [3]. The normal use of earthquake-damaged buildings after repair depends not only on the severity of the original earthquake damage, but also on the quality of retrofitting. It would be affected if the contractor is too inexperienced or if the repair process is too complicated to appropriately complete the retrofitting task [4]. Therefore, it is necessary to use building information modeling (BIM) and augmented reality (AR) to integrate and visualize retrofitting information, so as to improve the level of intelligent management in the construction process.  
As compared to a traditional retrofitting process based on two-dimensional (2D) drawings, the establishment of a BIM model can present structural information more visually [5], providing data for damage identification and methodical design. At the same time, BIMalso provides technical support for a paperless office, i.e., by discarding the shortcomings of traditional paper-based information that is difficult to search and save. It can integrate data generated during the retrofitting process, such as identification criteria, evaluation results, design concepts, cost estimates, and retrofitting methods [6]. Based on the results of retrofitting and renovation, BIM can use adaptive data to modify and update an original building model, e.g., to maximize the possibility of post-earthquake retrofitting construction and completion acceptance [7]. However, the lack of data synchronization between BIM and on-site processes is recognized as a primary barrier to BIM implementation [8; 9]. Traditional retrofitting construction sites also suffer from gaps in planning and execution, and a lack of interaction between project participants [10]. AR is the preferred method to solve the problems regarding the integration of BIM into construction. Combining AR with BIM and using its 3D visualization features to dynamically demonstrate retrofitting methods can facilitate communication and cooperative work. Nevertheless, representing the damage information in the BIM model and combining the BIM model with AR remain challenging.  
This study proposes a complete framework for BIM-AR applications, considering the above-mentioned problems in the post-earthquake retrofitting of buildings and the research statuses of BIM and AR. The main research in this study comprises building a seismic building BIM model, and then applying AR to visualize the model data. A BIM database is created to provide relevant technical and historical information, to share resources and models for future similar cases, and to lay a foundation for the construction of \"big data\" for post-earthquake buildings.