IFC-Bridge is an extension of the IFCs, specific to civil work structures, developed by the French transport research division SETRA, with the technical support of the CSTB (French Scientific and Technical Center for Building), as part of the official buildingSMART framework and through cooperation between its French-speaking, Japanese, Nordic and German chapters. This model, recognised as being fairly complete for bridges, has not yet been formally incorporated into the IFCs or implemented by software publishers.
As part of phase 1 of the MINnD project, in cooperation with the openINFRA initiative (with the backing of buildingSMART International), the current obstacles to the use of IFC-Bridge were identified and an action plan established to break down the barriers standing in the way of this extension being deployed.
An assessment of the current state of applicability of IFC entities to the establishment of an information exchange model for bridge construction was carried out in phase 1. This study is based on understanding of the ISO 16739 (IFC) standard and the work to prepare for an IFC-Bridge extension. It is also based on the “use case” analysis that led to the production of IFC exchange files based on the IFC ISO standard, therefore with building-oriented entities.
Regarding civil work structures, there are two categories of deficiency in terms of the IFCs:
- regarding the existing IFCs: incomplete implementation (extrusion, Boolean operations, etc.) or uses that are not really oriented towards the field of infrastructure (prestressing, etc.);
- regarding the field of civil work structures and the environment in which they are based: a need for new entities to be developed.
These two categories are detailed in the deliverable entitled “IFC-Bridge State of the Art & Missing Concepts”, written in English and available as part of the project. The deliverable concludes by identifying the concepts that are currently not correctly supported and proposing how the missing entities could be developed. The proposals must now be taken up by an international development team so they can be integrated into future versions of the IFCs.
It is also important to tackle these issues in the broader framework of the full set of information and models/simulations vital to the design-construction of structures as part of a “lifecycle” approach.
The aim of this working group was to create a multilingual data dictionary for the domain of bridges. A data dictionary comprises a library of objects together with their attributes, which describe the relationships between the objects as well as their properties. It thereby makes it easier to share and exchange information on the products manipulated.
In this study, the dictionary relates to the concepts used in the sector of civil work structures. This data dictionary therefore includes the constituent elements of bridges together with their English and French translations, descriptions, hierarchical links and characteristics. The aim of this data dictionary is to define the constituent elements of bridges so as to describe all types of bridge. Its comprehensiveness will be validated on a bridge project, for each design phase of the project. The dictionary will eventually be integrated into the buildingSMART data dictionary (bSDD).
The initial work has been finalised in compliance with the AFNOR/PPBIM standard (XP P07-150). It now remains to finalise integration into the bSDD, the international platform for the definition of construction objects.
It is therefore necessary to make use of all the concepts and tools available, with the support of the experts that have made this platform available to users, and consolidate the work done in order to check consistency with previous dictionaries.
Work done during the first stage of phase 1 led to the publication of an Information Delivery Manual (IDM) as part of the project to extend the IFCs to the domain of bridges. This IDM should fully cover the domain in a holistic manner in line with the most advanced professional practices. Its objectives are to fully explain the processes followed for a particular publication, and to justify their relevance, via the example of a bridge type that is sufficiently generic and common.
The approach taken was to start by following a line of de-integration/integration, intuitive for professionals, that detailed the components according to three views: the operational view (question: WHY is the bridge necessary? This constitutes the space of the problem posed), then the functional view (question: WHAT should the bridge do?), and finally the organic view (question: HOW or OF WHAT is the bridge made? These last two questions constitute the space of the solution). This subject was dealt with in a first Excel table, then projected into a second table over the lifecycle, which details all the states of the bridge components from creation to dismantling. During this last stage, it is possible to provide information on data exchanges (actors, content, phase) by using the BPMN system, for example.
Due to time constraints, the work provided during phase 1 only made it possible to partially complete the IDM. It was however possible to validate the pertinence of the process and approach followed, and identify all the major issues that the extension of the IFCs and IDM should aim to resolve to fully cover the domain.
- The IFCs are well-suited to the organic description of structures, but must be completed to ensure satisfactory cover of the needs of professionals (in particular, with regard to the elements describing the physical environment into which the structure must be integrated, and the elements relative to the procedural geometry of the solids generated that are vital for modelling or constructing these elements).
- The IFCs are also capable of describing the functions of structures, but are still insufficient or too rarely completed to fully cover the domain, and in particular all the functional modelling for bridges (traffic, mechanical resistance, foundations, etc.).
The IFCs are not appropriate for the operational views, and must be complemented by other categories to cover these views and manage the needs and requirements attached to the elements from the operational view up to the organic view; this management is vital to a full and comprehensive bridge verification and validation process. Having said that, this complementary context must be made explicit to allow development of an IDM that is truly suited to the needs and practices of the profession.
This action has made it possible to create a template that those in charge of developing future IFC standards could use for structures in the field of civil engineering infrastructures. This was achieved by harnessing the lessons learned over the past 18 months by the participants in the UC3 IFC-Bridge use case. More specifically, this work was done by:
- assessing the various global initiatives in the domain of infrastructures;
- compiling experiences and lessons from the UC3 sub-groups;
- highlighting the importance of a few key concepts such as the IDM (still fairly under-developed), MVD (Model View Definition – implemented fairly effectively), procedural geometries (rarely implemented in export formats) and glossaries (of which there are often numerous versions for a single domain);
- recalling the existence of existing IFC classes from which new classes could usefully be derived;
- proposing a list of infrastructure components or standard infrastructures grouped by major characteristics that could usefully be the subject of new IFC developments;
- ranking these components or standards according to their apparent economic interest and difficulties for end users.
 The IFC (Industry Foundation Class) format is an object-oriented file format used by the construction industry to exchange and share information between software packages.