# A Typology Model of Temporary Facility Constraints for Automated Construction Site Layout Planning
## 1 Introduction  
Construction site layout planning (CSLP) is one of the important processes that should take place for construction management to be successfully carried out before the commencement of main work. It primarily involves determining the type, size, and number of temporary facilities (TFs) installed and used temporarily at the site during the construction period (e.g., gate, access road, lifts, site offices, storages, laydown areas, security offices, toilets, hazard storage areas, and work areas) and identifying the relative locations between the facilities to support the efficient function of the site. Effective construction site layout contributes to minimizing travel distances, site congestion, time, and efforts required for material handling and transportation, and operational costs [1; 2; 3], and this, in turn, has a positive effect on the safety, sustainability, scheduling, and cost management of the construction site [4; 5; 6; 7].  
Despite such importance, CSLP still relies on experience, intuition, and previous construction site layout data. It is thus carried out manually in many construction projects today. However, this approach leads to difficulties in selecting appropriate temporary facilities and laying them out because the relationship between multiple temporary facilities included in a construction site layout is complex. There are also many limitations to be considered when installing them, and it is difficult to gauge the impact of construction site layout on construction labor and operation [8]. In addition, there may be variations in the quality of construction site layout as the planners' ability to collect data varies depending on the influence they have within the company. Therefore, CSLP is one of the most difficult tasks in site planning that requires human interpretation of the parameters and characteristics of the construction project and is thus a problem related to the optimization of the construction site layout performance [9; 10].  
To address this problem, studies on developing automated CSLP models using some optimization algorithms have begun to take place. Nevertheless, there are very few cases where these models are used in practice. One of the reasons is the insufficient application of constraints (i.e., the rules defined to achieve the layout goal of finding the location of temporary facilities on the site while meeting a set of constraints [11]) in CSLP, which leads to impractical construction site layouts [12]. In other words, constraints should be appropriately defined and checked to allow computer models to solve design problems [8]. However, the existing CSLP automation models do not take into account the constraints as thoroughly as construction site layout planners consider them when creating actual construction site layouts [13]. For example, a boundary constraint that temporary facilities should be laid out inside the site boundary, and an overlapping constraint that objects should not overlap are used by many construction site layout optimization models; however, constraints that deal with environmental and safety problems, such as noise and falling objects [14], and constraints considering geometric relationships, like maintaining a safe distance between site objects such as neighboring buildings and site elements, are rarely applied [15]. However, no attempts have been made to develop a constraint model for use in CSLP automation models through a systematic investigation of the constraints of temporary facilities applied in actual cases.