## 1 Introduction  
With the development and progress of society, the construction industry has developed rapidly, and the treatment of old buildings has also undergone great changes. Like old residential buildings, old dormitory buildings, etc., were built for a long time, with inadequate supporting facilities, their functions can no longer meet the needs of modern people's lives and work [1]. Like old factory buildings, old silos, etc., were idle or abandoned due to industrial transformation, resulting in a large amount of waste of building space resources [2]. The cost of demolition and reconstruction is large, the construction period is long and the environmental pollution is large. Therefore, the transformation and reuse of existing buildings has become a new way for the utilization of old buildings. For example, the Orsay Railway Station in the center of Paris was successfully transformed into the Orsay Museum, which achieved the functional change and exerted great value [3], and the \"Silo Wharf\" granary in Baltimore was regenerated into a complex of residential and commercial services, and has become a model of urban regeneration and a new landmark for Baltimore [4, 5]. Western countries began to pay attention to the research on the protection and renovation of old buildings earlier, and developed rapidly, which provided powerful theoretical guidance for the later research of building renovation [6, 7]. In order to better inherit the historical context of the city and promote green development. The state attaches great importance to the protection and regeneration of existing buildings. The Ministry of Housing and Urban-Rural Development of the People's Republic of China (MOHURD) issued a document \"Notice of the Ministry of Housing and Urban-Rural Development of the People's Republic of China on further improving the reservation, utilization and renovation of existing buildings in cities (JC [2018] No. 96)\" [8], proposing that all localities should fully recognize the value of existing buildings, adhere to the principle of full utilization and functional renewal, and attach great importance to and strengthen the preservation, utilization, renewal and transformation of existing buildings. On the whole, the renovation of existing building has become the best way to deal with old buildings reasonably. At present, the research on the renewal and utilization of existing buildings is gradually deepening. It mainly includes pre planning, planning and architectural design [9], operation and maintenance, energy and thermal comfort [10]. In addition, there are many other researches, such as accelerating the process of recycling old buildings through ecological sustainable development, adapting to the changing urban demand through ecological transformation [11], and proposing the energy-saving renovation strategy suitable for old buildings [12]. However, from the current research results, the past studies mostly focus on the design or operation stage of buildings. Compared with new buildings, the construction process of existing buildings has many unique characteristics. Firstly, the existing buildings have been built and used for a long time, and the structural components may be damaged to some extent, so there may already be some uncertain hazards. Secondly, there are many limitations during construction, such as site limitations, space limitations, instrument limitations and technical limitations. These will have a bad impact on construction safety. In addition, the construction period of the renovation project is relatively short, the safety management work is often neglected, and the safety investment is extremely small, the practitioners do not understand the characteristics and rules of the transformation operation, and there are blind operation and barbaric construction phenomena, which resulted in great potential safety hazards in the construction of existing construction renovation project [13].