*2.3. Problems for Investigation*

Clearly, it is up to the project team to choose the most suitable planning method with respect to the project context and the level of expertise of the project stakeholders. However, despite the fact that these methods have been used for decades, it should be noted that few construction projects have succeeded in achieving their initial objectives in terms of cost and duration [79]. Furthermore, traditional planning methods are very limited and unsuitable when considering the massive amount of data that the construction industry is producing on a daily basis over many construction projects. This knowledge base could be used to enable stakeholders to gain useful insights by using BIM and AI tools, as outlined by Gondia et al. [13] in their survey. Consequently, construction actors are increasingly adopting IT-based tools to develop more comprehensive, flexible, and efficient construction and planning methods, such as those based on BIM [80].

#### **3. Construction Planning and the Advent of 4D BIM**

BIM makes it possible to design, build and operate a structure over its entire life cycle [14]. It involves a collaborative process within the company and between external partners around a digital model. The latter can be described as a 3D representation of the physical and functional characteristics of a built asset [81]. It is a technical database, made up of objects defined by their characteristics and the relationships between them. The whole forms a structured set of information about a built asset. The 3D model is useful

for visualizing the planned project. However, on its own, this virtual structure remains static and does not allow a clear appreciation of the implementation of the construction process and the dynamic that characterises the sequence works. To make it dynamic, it is necessary to integrate a fourth dimension: time. This is the principle of 4D planning. In practice, this corresponds to linking the 3D elements of the BIM model with the project schedule activities. The next two subsections review the different applications and use cases in which 4D BIM has been used so far, and present a survey about the most-used 4D BIM tools, practices, and methods in France.

### *3.1. Review of 4D BIM Applications*

Research has shown that 4D BIM can be a solution to many of the deficiencies of current planning practices [26]. The enrichment of a 3D BIM model with scheduling data has increasingly improved the quality of the construction planning process through the development and integration of several use cases. For example, simulating the progress of work over time is an efficient communication tool for explaining to a client the progress of a project and the construction methods used. Indeed, 4D-BIM-based visualisations provide an intuitive comprehension of the construction process, which enables more effective communication and thereby better collaboration between all project stakeholders [38,39]. The use of 4D BIM has made several applications possible, including the following:


Furthermore, Candelario-Garrido et al. [37] have investigated the general benefits of using 4D BIM simulation for the construction industry and have estimated this tool and corresponding approaches to be 40% more efficient than conventional planning procedures. Linking the digital model to the construction schedule allows project managers to identify planning errors [39] given that 70% of traditional schedules produced are wrong and non-optimised [96]. Non-compliance with a schedule has a direct effect on the duration and costs of the work as well as possible indirect effects on its quality [97]. Extending incorrect schedules usually disrupt the smooth execution and coordination of works, and companies must use additional resources and accommodate the new activities within a very short time.

Despite the clear benefits of 4D planning methods, examples of their adoption, use, and application on real projects are rarely documented. Several research works propose 4D planning methods based on the development of specific and bespoke workflows requiring an advanced level of expertise in using many computerisation tools in different specialisation domains [98]. In addition, the use of 4D BIM is currently only adapted for small projects with few activities, rather than very expensive, time- and effort-consuming projects [23,31]. This is mainly due to the complex nature of 4D planning methods which are usually defined and based on interfacing BIM authoring tools (e.g., Revit, ArchiCAD, Bentley), BIM management tools (e.g., Navisworks, Syncro Pro), and legacy scheduling tools (e.g., Primavera, MS Project). There exists a lack of interoperability between the three groups of tools, since BIM authoring platforms are usually more suited to the design stage [23]. In particular, because of this lack of interoperability between BIM tools and BIM management platforms, the modification of any activity or 3D element generates a lot of manipulations, adjustments, and repetitions of the 4D planning process. Moreover, there is

a dearth of studies that investigate how 4D BIM can be integrated with AI tools which will enable the development of more effective methods for construction project management by considering the massive amount of data produced on every project and thus enable the gaining of valuable insights [40].

To capture the industry perspective on BIM-based 4D solutions and understand existing practices, a survey of French construction companies was performed. The results of the survey are described in the next subsection.
