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IFC4precast – a completely new concept for the precast industry

IFC4precast is a completely new concept to support the BIM process in the best possible way, especially for the precast industry. The digitization of the precast industry is progressing at a rapid pace, with the aim of supporting the participating software systems such as CAD, MES, PPS, and ERP with integration and networking. Several strong and well-known software vendors from this industry came together and founded the buildingSMART working group IFC4precast (initiated by customers).

The current development of BIM focuses on the documentation of the construction process by enriching and standardizing architectural and technical building models. The prefabrication process is not deeply anchored in this development at present. IFC is already used as the standard exchange format between architectural software systems, but the information it contains is lost during subsequent data exchange to specialized, precast software systems (CAD, MES, PPS, ERP). Current interfaces between precast CAD and MES are inflexible and very difficult to adapt to new requirements. The project aims to create an international, standardized interface that is maintained by the industry. As prefabricated products become more and more complex, the demand for a more powerful model data exchange interface increases.

At the end of the 1960s, digitization in the construction industry was pushed from drawing boards to CAD workstations. On this basis, many procedures and processes are very firmly anchored in the CAD systems. Through bidirectional data exchange between ERP, MES and CAD systems, tasks and know-how can be shifted to where they are needed.

The complexity of planning is reduced because production-specific settings are anchored and managed in the MES systems. For example, a planner will no longer have to worry about whether the element will be produced in a production plant in which a plotter, laser or robot works in order to limit the element dimensions.
Commercial data is exchanged with the leading system in the pre-built software environment, the ERP system. They guarantee a fast economic assessment as well as an economic optimization. A common database "IFC4precast" with a single unique key for built-in components reduces the often redundant data maintenance in several systems to a minimum.

From the point of view of the precast industry, an open, future-proof, effective and cross-industry solution is therefore sensible, involving ERP, CAD, MES and equipment manufacturers as well as manufacturers of built-in components.
The project aims to create an internationally standardized interface, maintained by the industry, based on interfaces already established in the prefabrication process such as AIA, Unitechnik Version 1.0 to 6.1, UXML, PXML, and BVBS. As prefabricated products become more and more complex, the demand for a more powerful model exchange interface increases.

The project is supported by the buildingSMART International Community and the project group consists of members of the industry. These are (in alphabetical order):

• AEC3 Deutschland GmbH (until the end of 2018)

• bwb Beteiligungsgesellschaft mbH & Co. KG

• iabi - Institute of Applied Building Informatics


• Precast Software Engineering GmbH

• Progress Software Development GmbH

• RIB SAA Software Engineering GmbH

• Trimble Germany GmbH

• Unitechnik Systems GmbH

The two spokespersons, Mr Benno Strack (bwb) and Mr Stefan Maier (RIB SAA), represent the Group externally. The technical work is divided among the following teams of experts:

- Reinforcement
o Spokesperson: Valentin Hellweger (Progress Software Development GmbH)
- Built-in components
o Spokesperson: Richard Borowan (RIB SAA Software Engineering GmbH)
- Component Modeling
o Spokesperson: Peter Kafka (Precast Software Engineering GmbH)
- Model Structure
o Spokesperson: Andreas Ellinger (Precast Software Engineering GmbH)
- Communication Schema (PRADAP)
o Spokesperson: Richard Hellrigl (Progress Software Development GmbH)
- Users
o Spokespersons: Benno Strack (bwb Beteiligungsgesellschaft mbH & Co. KG) and Stefan Maier (RIB SAA Software Engineering GmbH)
- Certification & Documentation
o Spokesperson: Klaus Linhard (iabi - Institute of Applied Building Informatics)

All important decisions are carried by the board, in which all companies listed above have the right to vote.


BuildingSMART International is a global institution that represents the nucleus for open BIM standards for installed values. BuildingSMART as an umbrella organisation coordinates the work between the regional chapters worldwide. The chapters consist of companies, educational institutions and private individuals from all areas of the building industry and they have set themselves the goal of using efficient methods of integrated information processing to make project management more consistent and effective and thus more reliable in terms of quality, schedule and costs.
The focus is on Building Information Modeling (BIM) as a planning method based on digital building models. The association designs and certifies standards such as IFC for an open BIM application. The Industry Foundation Classes (IFC) are an open standard in the building industry for the digital description of building models.
These defined standards are created for various building classes: rail, building construction, ports, bridges, etc. The IFC4precast group is currently working under the umbrella of the German Chapter, but also has close contact to buildingSMART Austria. Concrete support at buildingSMART Germany is provided by Mr Günther Wölfe (Managing Director) and Mr Mirbek Bekboliev (research associate). In order to give a brief insight into the activities and other working groups at BuildingSMART, here is a brief introduction to the young Austrian Chapter (founded in 2018) of buildingSMART with Mr Alfred Waschl as Managing Director.
The following working groups on the following topics have emerged from the goal of standardisation/digitisation of design, construction and operation at buildingSMART Austria (bSAT):

• Construction operation and construction industry – BIM regulations, cost calculation, construction time planning
• Digital building submission – Model testing in the context of regulatory requirements
• Building services engineering – Supplementing IFC data structures in the context of national technical building equipment requirements
• Classification and translation – Translation of IFC data structures in the context of national requirements
• Material and product – Development of mechanisms for the transfer of generic building materials and specific products based on the IFC data structure
• Infrastructure – Participation in the development of IFC data structures in the context of national infrastructure project requirements
• Software templates – Joint development of software configurations tailored to the requirements of openBIM projects
• BIM in operation – Development of mechanisms for the transfer of IFC-based digital models into building operation
• Training and Certification – Development of a uniform, multi-level, modular BIM training based on PCert

The working groups are very active and cooperate closely with international activities. Some of the bSAT working groups are served by comprehensive research projects, whereby a connection between practice and science is established.
The workshops are mostly conducted as webinars and enjoy great popularity at buildingSMART Austria. This made it possible to professionalise the work in the bSAT working groups considerably and to ensure the quality for the cooperation on international levels accordingly.
Within the framework of these activities, it has been possible to harmonise a number of large public-sector clients in Austria with a uniform standard for the tendering, awarding and implementation of digital construction projects. This includes the scopes of service for typical additional qualifications, the structures and contents of BIM regulations (AIA and BAP), and specifications for inventory recording and modeling. Due to these uniform specifications, it is much easier for contractors to calculate and carry out projects in planning and execution, as the specifications of the clients are understandable, calculable and comparable. This is an essential step in the introduction of the digitisation of design, construction and operation.

History and Motivation

At the start of the IFC4precast initiative, there was a feasibility study (2016) and extensive research to determine which format would be suitable for a new industry standard. From the feasibility study it was concluded that IFC4 is the right format. The following arguments speak for it:
• The precast industry demands a professional BIM integration of all software systems involved
• Current interfaces are limited in their possibilities;
o e.g. no 3D model description, no unique IDs for objects etc.
• The possibility of segmentation in IFC 4.0 makes it possible to display precast elements as well
• Some suitable entities already exist in the IFC 4.0 definition
• Good documentation tools available
• Broad support through standardised viewers
• Very good support by BuildingSMART in national and international sales and marketing
• Strong project group with market leaders in CAD, MES and ERP systems

Within the framework of quarterly personal meetings of the group, accompanied by regular telephone conferences, the definition and conception of the model exchange has been worked on continuously and intensively in recent years and months.


From the outset there were clear objectives within the group, which were defined as follows:
• Formation of a universal basis for process optimisation and information distribution in the precast area
• Bringing BIM ideas more into the precast area
• Coupling CAD and PPS systems even more closely with production
• Exchange over the international standard IFC, lifts the precast industry to a higher, more professional level in the field of the data exchange model
• Clear traceability via the building model and the building cycle
• Use IFC added value compared to existing interfaces
• BIM Collaboration Format should also enable bidirectional communication between the BIM Precast systems
• Small core project group that enables agile development of the interface
• Low project management costs
• No additional project managers/assistants
• Chairmanship changes among the project participants and includes keeping minutes and organising workshops
• Professional consulting and support in the field of IFC by AEC3 and IABI respectively


Looking at the different exchange scenarios in the precast element environment, it can be seen that there are different requirements with regard to the information content for each scenario.
In particular, the exchange between CAD and MES (control system, production) represents the most complex variant (see Fig. 1) and places very high demands on geometry, project and element structure as well as semantic data. This exchange scenario (exchange requirement) between CAD and MES is also the central part of the first phase of the IFC4precast initiative.

IFC4precast is currently already in the "Candidate Standard" step in the "Approval" phase. There were essentially two major milestones on the way there:
Creation of the Information Delivery Manual (IDM)
The requirements for data exchange are generally summarised in the IDM descriptions.
They fundamentally describe the scope and specifications of the information that a particular role (user) must provide at a particular time or work process in a BIM project.
Definition of the Model View Definition (MVD)
MVD stands for Model View Definition and is used to define a subset of the IFC data model (classes, relations, property sets, etc.) that is necessary to meet certain exchange requirements. It was developed so that, when exchanging data between BIM software applications, the whole model is not exchanged, but only the subset that is needed in the process in which the data exchange takes place – in our case the focus of the IFC4precast MVD is only on the precast element area. MVDs always refer to a specific IFC version (e.g. IFC2x3 or IFC4).
The results of the work were presented and discussed internationally at expert panel meetings. Based on the feedback from these meetings, the concepts and results were adapted accordingly.


Figure 3 shows the entities and relationships between the objects from the perspective of the precast user. The example of the electrical box (bottom right) also shows that all components and model sections are traceable back to the building model, identifiable via unique IDs.
Figure 4 shows the main structure (as a UML diagram) of the object model on which IFC4precast is based.

You can use this object structure to define all known structures of precast elements. The example in Fig. 5 shows a wall with internal insulation – you can see the possible division into different parts, layers, surfaces and materials.

Concepts for exchange
Together with model and exchange definitions, information was summarised into specific concepts. The information units between which we can distinguish are the following:
1. Identification
2. Geometry
3. Placement
4. Material
5. Type information
6. General semantic information (Properties)

The concepts are explained in detail in the following sections.
The purpose of this definition is to give the corresponding functional part a human-readable identification, i.e. the name and description of the particular object instance. In this way, each object in a project can be distinguished from an object of the same type by manual checking.
Due to specific geometrical information requirements for the automatic production of precast elements, different types of elements must be supplied taking these requirements into account. For example, bending machines for rebars require the geometry to be supplied as a series of linear segments and bending radii as well as a diameter of the bar. On the other hand, a part of a precast element is best described with a boundary surface model (b-rep), with which volume calculations and collision detection can be carried out.
The main requirement for placing different elements in precast structures is that they are relative to their parent element. This means that a socket placement refers to the higher-level precast element in which it is installed. As a result, the socket moves with its parent.
This involves the assignment of an individual material to parts of the precast model.
Type information
Information types must be defined for a seamless exchange. The MVD should have a clear taxonomy of elements with specific definitions. Serves as a basis for communication and clarity.
Cover specific semantic information of certain types. Exchange requirements for specific fields are defined individually in each exchange.
A classic example – the thermal separation
The thermal separation is usually placed at the edge of an element with reinforcing bars protruding from the element (often used on balconies).
This part is a special type of insulation with additional reinforcing bars, which are an integral part of the built-in component. The insulating section usually has a cuboid shape, while the reinforcing rods have a cylindrical shape and are usually not bent. In existing industry-standard interfaces, it was previously not possible to transfer the exact model accordingly in order to be able to take all details into account in production. In the case of IFC4precast, the structure looks as follows:

The IFC object "ComplexObject" represents the thermal separation, which is divided into reinforcement and insulation; each of these IFC objects also contains a detailed description of the geometry and specific attributes. This allows the model to be transferred to the subsequent software systems without losses.


The added value for the user of IFC4precast is manifold, also given by the change of processes and working methods. Although the full implications for the user cannot yet be estimated, the following added values can already be predicted or seen in reality today:
- Higher information content and therefore better understanding of the data
- Model-based communication and visualisation prevents misunderstandings and errors in production
- Lossless transfer of information between CAD, MES and ERP
- Visual interpretation compared to the plan
- Better collision detection
- Display and analysis in 3D using viewers
- Free IFC viewers without industry-specific special solution
- Interdisciplinary data exchange (e.g. with customers, BIM + data exchange, inspection engineers)
- Fewer interpretation possibilities due to clarity of 3D data compared to 2D plans
- Technical improvement (GUID, reinforcement in 3D, formwork part interpretations, etc.)
- Plant-independent planning of production
- More flexible working
- Smart Factory by means of 3D data, thus also more possibilities directly in the plant
- Technologies such as VR (virtual reality) or AR (augmented reality) require 3D objects
- Formwork recognition through analysis of the 3D element geometry
- Easier troubleshooting

Current status & outlook

In the final phase up to the final standardisation, the documentation has to be completed and all necessary information has to be made available to IFC in a schema-compliant manner. The first successes were already achieved in spring 2019, when the floor slabs based on IFC4precast were produced by a precast element manufacturer (from Germany).

The standardisation process for data exchange between CAD and MES systems in the precast industry should be completed by 2020 at the latest. From this point on, software companies can be certified for IFC4precast – there will be a special certification program for this under the umbrella of buildingSMART.
At the same time, the IFC4precast group is already working on new topics, such as a system for the cross-manufacturer exchange of article data, keyword "PRADAP".

PRADAP (Precast Article Data Access Protocol) is a new concept that enables the synchronisation of article data across manufacturers without having to abandon the existing component catalogues. PRADAP does not strive for a central database that replaces everything else, but rather introduces a lightweight, easy-to-implement communication method that links the existing article catalogues with each other. For this project we are already working together with some manufacturers of built-in components.

Work is also already proceeding on a further exchange scenario between ERP and CAD, MES. The commercial data also need to be considered when exchanging.


BuildingSMART International: https://www.buildingsmart.org/
BuildingSMART Germany: https://www.buildingsmart.de/
BuildingSMART Austria: https://www.buildingsmart.co.at/

CPi worldwide journals are trade journals for the concrete and precast concrete industry that are published in 10 different language editions in more than 170 countries. These trade journals, with their practical editorial reporting on research, production and applications, are specifically addressing the decision makers of the concrete and precast concrete industry.

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