From BIM-enhanced coordination to digital twin: Bimsync to coordinate the extension of Lyon's subway

However, this approach would not have been possible without the implementation of a certain number of operating principles within the team:

• Weekly summary meetings, with exclusive use of the platform and "topics" to report on decisions made;
• A frequency of updating by the contractors of their models; 
• The possibility for everyone to open issues, whether it is a need for adaptation (for example: "modification of a reservation"), a request for clarification or an alert, in compliance with the user charter; 
• The development of a simple but robust validation workflow, based on the use of issue's "statuses" (open, for action, in progress, closed, etc.) and the party requesting". Thanks to this metadata, it was easier to know the status of each "issue" and to clearly delimit the responsibilities between the project management (Design coordination team, contract managers) and the contractor's managers.  

Continuous integration of "as-built" models 

The Building Information Modeling (BIM) approach used for the extension of the metro line B enabled the integration of "as-built" digital models in the digital mock-up throughout the construction phase. 

Indeed, at the end of each elementary construction operation, it was important to pay particular attention to the fact that the digital model of the project was updated and thus directly reflects (or almost) the project actually built. This "As Built" information, thus integrated into the exchanges of the Synthesis meetings, helped to adjust the execution studies with the concerned construction actors, as soon as possible. 

What are the benefits of this "live" digital model? 

First, there are fewer hiccups in the field during the construction phase and fewer last-minute on-site adjustments (widening a reservation, adjusting a culvert, etc.), as can be the case with a traditional synthesis process.

The other advantage of this method is to prepare the digital O&M model (Operation & Maintenance model) at a lower cost and with a better level of reliability, but also to deliver a first version of the "digital twin" (see below) meeting the needs of operators and maintainers as soon as the project is commissioned.  

Indeed, the updating of the digital model as it is produced makes it more reliable and more consistent with reality. Indeed, it allows a continuous control of the quality of the digital models, which leads the actors of the construction to improve continuously in the generation of the digital models. On the other hand, as the digital model of the project is used by all the actors of the team, they are in the first position to identify the errors in the models and to come back on the proposals of corrections.

Finally, the continuous updating of the model saves the client the frustrating and potentially costly task of analyzing and auditing the digital model made available at the end of the BIM project. This is when teams start to lose motivation and it is difficult to consolidate information.

Other uses of the BIM approach

By adopting a collaborative approach, the project actors have progressively developed other uses of the models for their activities ("BIM uses", in the vocabulary of BIM Managers). Here are some examples:

• Simulation of the coverage areas of the video protection cameras: the modeling of the visibility cones of the cameras and the possibility of previewing, in the 3D models, the fields of view offered by each camera have made it possible to avoid tedious test campaigns and have limited the last minute adjustments, or even the moving of cameras. 

• The materialization, in the digital models, of the trains stopped in the stations. The latter, often absent from the "technical" digital models of the stations, allowed the automation specialists to project themselves into the complete context of the stations. They were able to verify the positioning of the train stopping points and propose, before the installation phase, adjustments that would have been difficult to see on a simple two-dimensional diagram.  

• Assistance to the production of execution plans by the project management teams. The works contracts require the production of execution plans from digital models, with updates in a cadenced way on Bimsync. This allowed us to use the updated models during the control of the 2D plans and thus to facilitate and make our visa more reliable, in particular concerning the control of the good taking into account of the different reservations requested by the third party lots via the BIM platform.

• Identification and qualification of drilling zones in tunnel segments. The modeling of the segments by the civil engineering companies has allowed to communicate more clearly the constraints related to the drilling possibilities. In addition, it has led to a faster development of the interfaces between the tunnel equipment installers and the civil engineer, who is in charge of digging the tunnel with the tunnel boring machine. 
• Finally, the accessibility of certain sensitive equipment (fire hydrants) for emergency services was verified, as well as the conditions for transporting bulky equipment for installation or replacement. The creation of "empty" volumes in the digital mock-ups helped the construction team to keep in mind and "visualize" the existence of these constraints throughout the construction process. These requirements thus crystallized in the models  make it possible to limit the risks of loss of information, at the time of the departure of a specialist, which is not rare on a project of such a scale! 

To the digital twin!

As a result of the structure set up during the construction phase, the digital model could be a "high-fidelity" reflection of the terrain. This virtual representation, called "digital twin", is made up of objects modeled and filled out in 3D. It should benefit asset managers and those responsible for the maintenance of public infrastructure.

Although digital, this twin is a new asset in its own right. Thus, in order for it to remain valuable to operators/maintainers, asset managers, but also to those in charge of tomorrow's construction projects (extensions, upgrades, etc.), it will need to be updated and managed throughout its lifespan.