# Algorithm of Smart Building Supervision for Detecting and Counting Column Ties Using Deep Learning
## 1 Introduction  
The Republic of Korea suffered building collapses from the Pohang earthquake in 2017. The walls of apartments collapsed, the exterior brick finish of a university was removed, the pillars of piloti buildings were damaged and the buildings themselves collapsed (Figure 1). For this reason, the Building Act of Korea strengthened supervision work by adding supervision submission documents upon completion, as well as the building supervision of the 3 rd floor or more of pilot buildings in cooperation with structural engineers [1].  
In fact, in the Pohang earthquake accident, the pilot buildings collapsed due to the damage to the pillars on the first floor of the buildings, and the structural weakness of the piloti structures along with the omission of rebars during construction are considered the cause of the collapse [2]. Therefore, this legislation was established under the judgment that the structure of the piloti is vulnerable as a structure in response to safety accidents, and at the same time, it has the purpose of preventing insolvent construction by strengthening the contents of the supervision system.  
As part of an effort to improve the quality of buildings, the supervision system has been strengthened. However, completing all the items in the supervision system and getting them all down on paper is not an easy task. In the case of the omission of the rebars related to the Pohang Earthquake, even though counting the rebars is mentioned in the checklist of the supervision guide, it is practically difficult in the field. It is not easy for the supervisor to secure the time to count individual rebars at the building site, which becomes more difficult at the site of large buildings. Even if the number is counted, the supervision work is not limited to counting the rebars; so, even if the rebars is an importantfactor in supporting the stress of the structure, it is difficult to actually perform this task in supervision.  
Recently, new technologies of the 4 th industry are being researched and utilized in many fields. The development of new technologies is accelerating, and efforts to increase efficiency by utilizing these new technologies are being attempted in many fields. In addition, unmanned-based automation technologies, such as drones and robots with artificial intelligence, are replacing those jobs previously believed to only be possible for humans, and it is not uncommon to see better results than humans. Moreover, in the architectural field, 'Constructch', which combines Construction with IT technology, is leading the construction industry upward, which was considered to be a downward trending industry [3], and the premise of this trend is IT-based technology, BIM (Building Information Modeling).  
Therefore, in this study, we used these new technologies, focusing on rebar counting, especially the horizontal rebar, known as tie counting, among the various tasks of supervision, to improve the possibility of practical supervision work and improve the efficiency of work, and furthermore, to see the possibility of using convergence technology.