5.2.2. Phase 2: To Identify Information Requirements and Relevant Workflows

**Step 2** (*here Step 1 is not necessary*): To determine the information to be produced for each 4D objective (Table 2), the BIM manager must understand how 4D BIM tools work. The more this BIM actor is aware of the latest technological advances, the more technically and economically viable its 4D planning strategy is. Thus, a review of existing 4D BIM tools may be necessary if this use case is not usually implemented by the BIM manager.


**Table 2.** 4D information requirements related to the 4D BIM use case.

**Step 3:** BIM modelling and collaboration platforms were imposed. A workflow was established based on these tool constraints. However, no 4D planning tool nor project participant with expertise in using this tool was involved in the project. Therefore, the following two assumptions were made:

*Hypothesis 1***.** 'The BIM manager masters the 4D planning tool. If necessary, he can be called upon to resolve the technical problems encountered.'

*Hypothesis 2***.** 'As soon as the phase is launched, under the responsibility of the BIM manager, the project OPC is introduced to BIM and sufficiently trained to master the 4D planning tool.'

As for the Nanterre 2 project, Hypothesis 2 was relevant, since the BIM manager had had expertise with regard to using Synchro Pro in previous projects. Therefore, the workflow proposed and implemented is illustrated in Figure 7.


**Figure 7.** Tools and methods for producing 4D BIM deliverables.

5.2.3. Phase 3: To Design a Project Schedule Adapted to the Use of 4D BIM

The process represented in Figure 8 can be attached to the project's BEP in order to guide stakeholders in designing and developing schedules that are suitable for the 4D BIM

use case. The following steps should enable the BIM manager to transform the traditional project planning process by taking into account the 4D BIM objectives.

**Figure 8.** Summary of Phase 2's process - Design of the project schedule adapted for the use of 4D BIM.

**Step 1:** The traditional schedule is used as an input. This document is produced by the project OPC through combining and including all business planning of the project. The project tasks flowchart is of level 3 (Figure 9).


**Figure 9.** Screenshot of Nanterre 2 CESI project schedule.

**Step 2:** The first objective that must be studied is the identification of periods that could represent a certain risk and for which 4D planning can provide an added value in terms of safety and space optimisation. The previously identified actors must analyse the sequencing of the tasks of the initial planning and list each of its periods in order to study them in detail.

**Step 3:** The second objective is to produce the information listed by the BIM manager in Phase 2. Collaboration between project stakeholders should enable the production of precise information and allow for the performance of a first optimisation for the initial planning. Thereafter, 4D planning will enable the optimisation and the validation of the planning generated. At this stage, all of the 4D parameters related to the analysis of occupied spaces (4D BIM Objective N◦ #1) are known. As for the 4D objective linked to monitoring construction work progress, it is up to the OPC, possibly with the support of the BIM manager, to choose their own method. For the Nanterre 2 project, the initial schedule already included the links between the tasks. It therefore remains to determine the 4D parameter to be created so as to link the schedule to the BIM models, and to increase the level of the project tasks flowchart in order to optimise the precision of the progress monitoring process. Since the BIM model was created using Autodesk Revit software, a simple and straightforward solution is to create a text parameter and name it '*BIM\_WBS*'. This parameter is created and assigned to all the BIM model objects. Then, the exact name of the planning task to which it must be linked needs to be entered. By doing so, it was possible to automatically assign all the objects of the BIM model to the project schedule. Table 3 summarises the information produced.

**Table 3.** Summary of the information produced at Step 3 of Phase 3.


**Step 4:** Phase 3 ends when all the information produced is gathered and combined. Using the initial schedule, the OPC transforms all tasks by integrating 4D information, and then shares the resulting schedule with the MOE for approval (Figure 10).


**Figure 10.** Evolution from initial planning to final planning (screenshot from Microsoft Project).

#### 5.2.4. Phase 4: To Supervise BIM Models Production for 4D BIM Use Case

This phase allows the project contractors to integrate 4D BIM information into their BIM models to achieve the 4D BIM objectives of the project. By relying on the project BEP, construction companies must be able to use the information provided in the schedule resulting from phase 3.

**Step 1:** The BIM manager must indicate in the BEP the main BIM objectives of the project. At this stage, the project BIM contributors should be informed that a 4D planning process will be implemented. The BEP section following the general objectives must indicate in detail and in a SMART way, what the objectives of each BIM use case are, and in particular, the objectives related to 4D BIM.

**Step 2:** This step consists of precisely determining the degree of responsibility and involvement of each project participant towards the achievement of the 4D BIM objectives. Therefore, it was necessary to use the RACI matrix templates proposed in Figures 4 and 5 and substitute the actor names by the actual companies that will execute the project.

**Step 3:** The two production processes given in Figures 8 and 9 were integrated into the project BEP to explain to the BIM contributors how the 4D BIM use case should be implemented.

**Step 4:** Once the objectives have been identified and the production methods thoroughly detailed through Steps 1, 2 and 3 of the current Phase 4, the workflow to be implemented was clearly explained to enable efficient project communication and information exchange.

#### *5.3. 4D BIM Planning Implementation*

In this section, the 4D planning of structural works of the Nanterre 2 CESI project is performed. The initial planning is first linked to the digital model without taking into account the 4D BIM objectives of the project. Then, the proposed method is applied to integrate the information produced in the previous subsections.

#### 5.3.1. Primary 4D BIM Planning

First, the 4D parameter 'BIM\_WBS' is created and integrated into the BIM model of structural works. Then, the BIM model is exported from the authoring platform using the Synchro Plug-in. The project schedule is also imported and the links between the tasks are preserved. Finally, the objects of the BIM model are assigned to the corresponding tasks. This first summary 4D BIM schedule, which can be exported in video format (.AVI) or in phasing form (.JPEG), allows project teams to check that the project workflow is correct. It is now possible to work directly on the 4D planning software to make changes to the project schedule. However, the BIM objectives of the project have not been achieved yet.

#### 5.3.2. 4D BIM Planning According to the CESI Method

To test and validate the proposed method, it should be confronted with realistic cocontracting issues. To do so, the primary 4D planning performed in the previous subsection was used along with a detailed scenario including periods where four tasks overlap, and three companies 'coexist' on the construction site. The 4D parameters to be produced to meet the 4D BIM requirements of the Nanterre 2 project have been identified in Section 4.2. The OPC integrates this information into their planning (see process in Figure 8) while companies make the necessary changes to fill in the information in the BIM models (see process in Figure 11). The compilation of these two deliverables makes it possible to create a more detailed 4D plan which was used to validate and/or optimise constructive choices. Figure 12 illustrates the result of 4D BIM planning. By creating the spaces linked to each activity, an analysis of the workflow can be performed to detect hazard sources and reduce their impact. In this planning scenario, it has been detected that the work areas on the ground floor overlap during HVAC and ELEC interventions. Preventive actions can therefore be taken to manage the space where these two activities are located so that no hazards due to this co-contracting slow down the work progress.

**Figure 11.** Summary of the Phase 3 process - Supervision of BIM model production for 4D BIM use case.

**Figure 12.** 4D BIM planning of the Nanterre 2 CESI project using the CESI method.

The 4D BIM planning performed using the proposed method enables the achievement of the client's objectives better than the primary 4D planning. Indeed, the use of 4D information, identified from the second phase of this method, allowed the actors to focus effectively on the expectations of the MOA (namely, the evaluation of the result of 4D BIM planning with regard to the 4D objectives) as shown in Table 4.


**Table 4.** Proposed method evaluation regarding the client's 4D BIM objectives achievement.

#### **6. Automating 4D BIM Planning: The RINNO Case Study**

Research leveraging the use of 4D BIM data using AI tools is lacking [13] although such an integration is crucial to optimise and develop more effective strategies for construction project planning through the development of automated tools to, for example, automatically generate and simulate different scenarios [40]. Furthermore, there is a dearth of methods and tools dedicated to renovation project management. New construction projects have usually been prioritised in terms of design, planning and management tool development. When possible, these tools are adapted to the context of renovation projects [100] which represents one of the main factors that make their performance typically lower than that for new constructions [101,102]. The research study reported in this section is part of the RINNO research project [103,104] which aims to develop a holistic multi-disciplinary platform that will ensure the acceleration of the rate of deep renovation in EU residential buildings. Here, an ontology is introduced, and its application is illustrated within the context of building renovation. Ontologies are useful AI tools in formalising specific domain knowledge, including their concepts, relations, and constraints [41]. They enable process automation and tool development as they provide a machine-readable representation of knowledge.

#### *6.1. Renovation 4D Planning Ontology*

Figure 13 presents the ontology developed within the RINNO project [103,104] dedicated to generating 4D BIM schedules for renovation projects. The overview given in Figure 13 is a UML (Unified Modelling Language) class diagram illustrating the ontological concepts, their relations and constraints, as well as the attributes or properties that define each concept (here class or entity) to facilitate its implementation as a renovation knowledge base in the case of this study.

As presented in Figure 13, a 'Built Asset' is composed of several 'Building Elements' (e.g., windows, walls) and WBSs (Work Breakdown Structures, e.g., floors, external façades) where each 'Building Element' belongs to a WBS. A 'Building Element' requires one or many 'Renovation Activity' components to be renovated, and this may be carried out by installing one or many 'Innovative Products' (e.g., photovoltaic panels, solar collectors). Each 'Renovation Activity' is temporally constrained by activities that should start and finish before it, whereas some others will be triggered and executed after its completion. It also requires a set of 'Material', 'Workforce', and 'Equipment' so it can be executed and may cause 'Disruption' to the building occupants. The 'Disruption' concept is beyond the scope of this paper and will be detailed in future research, since its estimation and simulation is one of the RINNO project targets.

The ontology proposed was populated into a database using the SQL Server. This database included several tables, and each one enabled the implementation of a concept from the ontology. The tables describe in detail data related to renovation activities, their

sequencing rules, constraints, duration, cost, equipment, etc., all gathered, structured, and verified with the help of the RINNO project partners.

**Figure 13.** Renovation 4D planning ontology—UML class diagram.

*6.2. Automated 4D BIM Planning and Simulation Process*

Figure 14 presents the system architecture of the digital tool developed and Figure 15 the automated 4D BIM planning process implemented; both are based on the ontology introduced in the previous subsection. The automated process, represented here as a UML scenario diagram, enables the BIM manager to leverage the BIM data and automatically generate and simulate the 4D BIM planning based on a renovation scenario identified at the beginning of the process. Indeed, after checking the BIM model and selecting a renovation scenario via two main GUIs (Graphical User Interfaces) (Figure 16C,D), the 'RINNO Renovation Engine' component coordinates the 4D BIM planning process by: (i) updating the BIM model if necessary to integrate project-related information (Figure 16A); (ii) generating traditional (Gantt) planning using (a) the scenario selected by the BIM manager in order to identify WBS, renovation activities to be performed, and equipment used, (b) the BIM

model to extract BIM elements considered by the scenario simulated and corresponding quantity take-off (QTO), and (c) the ontology to map activities to WBS and BIM elements and assign relevant equipment to activities and estimate their durations; (iii) updating the BIM model using the traditional planning generated, particularly by integrating the activities data and initialising the 'WBS\_BIM' parameter; and (iv) simulating the 4D BIM planning created through the BIM management tool.

**Figure 14.** System architecture of the 4D BIM digital tool.

**Figure 15.** Automated 4D BIM planning and simulation.





**Figure 16.** RINNO Renovation Engine GUI. (**A**) Project details interface. (**B**) WBS interface. (**C**) Scenario interface 1 for renovation activities selection. (**D**) Scenario interface 2 for renovation equipment selection.

Figure 16 illustrates the GUI of the RINNO Renovation Engine developed to: (i) facilitate interaction with the tool; (ii) automate and assist users for renovation scenario definition and generation; and (iii) streamline the whole automated 4D planning and simulation process.

#### **7. Discussion, Conclusions, and Perspectives**

This work was an opportunity to study project management in general, and then to look at the new methods that have emerged with recent technological advances. Traditional planning methods are often ineffective in taking into account all the uncertainties and hazards that may occur during a construction project. As a result, time and cost targets are rarely met. BIM represents an evolution of these practices and can be a useful way to optimise planning methods. Numerous studies show that 4D BIM helps to reduce planning errors, promotes collaboration between stakeholders, and helps project teams make effective decisions.

#### *7.1. The Nanterre 2 CESI Project Case Study*

The first case study showed that not all actors can afford to innovate and adopt BIM for project management. Although the use of 4D BIM was specified and required by the client, it was not implemented in the Nanterre 2 CESI project, mainly due to a lack of practical and simple methods of implementation, as well as the low and heterogeneous level of BIM training and expertise of the project actors.

To contribute to the democratisation of the 4D BIM use case, a structured and practical method was proposed. This method was based on a four-step process to enable project participants to (i) clearly and in a SMART way, express the 4D BIM objectives from the beginning of the project in the BIM specification document, (ii) identify information requirements and relevant workflows to achieve these objectives, (iii) design an adapted 4D BIM plan, and (iv) supervise the BIM model's production to enable the implementation of the 4D BIM use case. The proposed method promotes collaboration between project actors and guides them towards information production and management. Pragmatic and detailed processes and methods were introduced and applied on the Nanterre 2 CESI project to implement the 4D BIM use case and related objectives required by the client. This implementation enabled the illustration of some of the advantages 4D BIM can bring to a construction project. The effective adoption and development of 4D BIM can provide efficient tools for monitoring work progress and so represents a significant added value to ensure that time and cost constraints, when initially planned, are constantly satisfied. Sacks et al. [105] proposed a matrix that contains 56 interactions between Lean methodology principles and BIM functionalities to clarify possible synergies between the two methodologies. Using this matrix as a starting point to develop the proposed method would have enabled more pragmatism and better streamlined and optimised processes alongside the workflows proposed in this paper.

Furthermore, it should be noted that objective N◦ #2 (i.e., 'At any time during the construction phase, 4D BIM planning must enable measuring construction works progress within +/- 3 days') was difficult to achieve. This objective should be studied in detail so as to clearly understand what the actual intention of the client was. Objectively, 4D BIM provides very little added value for monitoring the work progress when data are not collected in time and the BIM models are not updated regularly. Indeed, the accuracy of the work progress depends on the frequency with which the OPC carries out their onsite supervision and monitoring missions. In general, clients have little knowledge of the possibilities and limits of digital tools. It would be very difficult to visualise the 'exact' onsite work progress as it would require a BIM model containing each element, equipment, or work structure installed and used, temporary or permanently, during each construction phase. Therefore, the assistance of an AMO BIM to help the client express and formalise their requirements in a SMART manner is crucial. Furthermore, IoT and autonomous systems [106] can play a fundamental role in collecting onsite data efficiently and regularly so to enable the automatic and regular updating of BIM data.

Moreover, the proposed method, if it were to be implemented in more typical circumstances, would require certain levels of collaboration between key project actors. The two RACI matrices (Figures 4 and 5) show the required interactions between key project actors for the effective integration of the two processes (construction schedule and BIM model creation). The collaboration of these key project actors is crucial. The issue of collaboration is frequently raised when the realisation of the benefits of BIM are considered. Increased collaboration is not only a prospective beneficial outcome of BIM adoption [107]; it is a prerequisite for the full attainment of these potential benefits [108]. Thus, studies have suggested that the realisation of BIM's key benefits relies upon the degree of collaboration achieved and that this is not achievable with traditional project procurement approaches [109–111]. Objectively, the adoption of 4D BIM provides very little added value without the necessary and timely integration of construction scheduling and BIM model creation; a process that is difficult to achieve in traditional project frameworks.

The Nanterre 2 CESI building has been open to students since September 2019. The operation and maintenance management of this building is expected to be implemented using BIM technology. To undertake this, it is essential to implement and use a classification system such as Uniclass 2015. Based on a set of consistent and hierarchically organised tables, Uniclass 2015 allows the classification of all types of elements that could be considered in the context of a construction project, from the most complex items such as industrial or residential complexes, to the most detailed items such as door locks or the covering and finishing of products. This system also allows for the classification of physical objects using the 'Entities', 'Elements', 'Systems' and 'Products' tables, as well as construction processes and activities through the 'Activities' table. Consequently, it allows for the simultaneous integration of PBS (Product Breakdown Structure) and WBS [51] and therefore the implementation of BIM for the operation phase in which the building objects are linked to their respective operation and maintenance activities. This ontological link between objects and activities should also enable the standardisation and automation of 4D BIM planning and simulation for both construction and operation phases.
