# A Typology Model of Temporary Facility Constraints for Automated Construction Site Layout Planning
## 2 Literature Review  
CSLP automation models commonly apply boundary constraints to ensure that all temporary facilities are located within the site and the non-overlapping constraint to prevent the objects from overlapping. However, in these models, constraints are considered differently and perceived in a limited manner (Table 1). For example, [PERSON] et al. [6], who attempted to solve the construction site layout problem through a genetic algorithm with the cost of transportation or removal as a layout evaluation value, used constraints to limit the placement of material storage in hazardous areas and to prevent noise-producing work areas from being placed close to the office. [PERSON] and [PERSON] [35], who proposed a mathematical optimization-based model used constraints to make some temporary facilities be placed adjacent to each other or separated from each other and to make some objects be seen at specific locations on the site. [PERSON] and [PERSON] [36] who proposed an automated framework to create a dynamic site layout model by utilizing Building Information Model (BIM) used constraints to ensure that specific temporary facilities are within the radius of a tower crane and to maintain a buffer distance between the pathways and temporary facilities used commonly by trucks and machines for smooth site operation and labor safety. [PERSON] and [PERSON] [31], who proposed a framework using heuristic optimization through a genetic algorithm, used constraints related to the size of temporary facilities to be placed. Meanwhile, there was also a case of developing an integrated framework and model for minimizing construction site risk using only boundary and non-overlapping constraints [37]. Such insufficient applications of constraints in CSLP may lead not only to an inefficient travel path during construction, but also to an increase in costs incurred from the installation and relocation of temporary facilities, and ultimately have a negative impact on the construction site layout optimization [38]. Therefore, it is necessary to identify and apply various constraints that can be derived from historical data such as past similar projects [14; 37]. Additionally, some research [39; 40] has noted that in the case of a construction project that has multiple phases, the task of entering repeated data (i.e., constraints) for each phase can be tedious. Nevertheless, in relation to the existing CSLP automation  
Figure 1: Frequency of temporary facilities appeared in construction site layout planning (CSLP) automation papers. models, there has not been a constraint model that could be comprehensively used to create a practical construction site layout [24]. In addition, although constraints in construction site layout are heuristic factors that should be used by combining knowledge from experts or literature, there was a lack of efforts to find out the constraints that are actually applied to temporary facilities through a close examination of literature and expert knowledge. These limitations necessitate the development of a constraint typology model that identifies constraints comprehensively, classifies them into constraint types, and presents computational modeling methods for each of the constraint types that can be utilized in the layout of temporary facilities in CSLP. In addition, the constraint types used in the existing CSLP models have different names despite being the same functions. For example, constraints that place temporary facilities on the site boundaries are called \"region constraint\" [35], \"boundary constraint\" [34; 41], or \"being inside the boundaries constraint\" [31]. The constraint for laying out or not laying out temporary facilities in a specific region has been called the \"object-region constraint\" [35], \"exclusion/inclusion-zone constraints\" [41], or \"available site space constraint\" [36].