Keywords

1 Motivation

At present there is a dynamic environment which, in the name of environmental protection, places high demands and new framework conditions on the entire sector of the construction industry. In addition to government measures and legal regulations, the construction industry is independently able to determine the demand for cement and thus regulate one of the largest greenhouse factors. Cement and concrete are of great importance for construction and infrastructure projects, but their impact on the greenhouse effect is just as great. The production of cement, the binding agent in the manufacture of concrete, alone accounts for around eight percent of global CO2 emissions. In addition, with the exception of a few aggregates, all the starting materials for concrete are primary raw materials, the extraction of which requires energy and impairs or even destroys the landscape and nature. Wood as a storing product for carbon offers a promising alternative here. Buildings are considered to be the most sustainable storage facilities because they have a long-lasting life cycle [1]. In scientific comparative analyses, it has already been demonstrated that building constructions made of wood can save up to 56 percent greenhouse gases compared to a mineral-based one [2]. This can be further increased through cascade use. An essential cornerstone in the further development of sustainable urban concepts is still the affordability of building and living. The building culture in Germany emphasizes these points and seeks to reconcile the ecological, economic and sociocultural dimensions. In Berlin concrete measures and recommendations for action are based on the resolution of the Berlin House of Representatives of March 21, 2019. Under the title “Sustainability in construction: Berlin builds with wood” [3], wood as a building material is to be used to a much greater extent in Berlin and, as a carbon dioxide reservoir, contribute to climate protection and resource efficiency. In doing so, the Senate is called upon to support forestry, crafts, industry and science in order to develop Berlin-Brandenburg into a region of timber construction. However, the increased use of wood as a building material for multi-story residential buildings requires an increased industrial scaling of the manufacturing processes. Therefore, the development of a horizontally and vertically digitally networked value chain for urban housing construction based on an economic and resource-efficient production system is required. Focusing on the wood construction sector of course such an approach has to tackle various challenges.

These major challenges exist in following areas:

  • High re-planning efforts for prefabricator due to regulatory restriction in Germany prohibiting involvement of executing companies in planning processes of building

  • Missing flexibility of prefabricators in transferring individualized architectural designs into production systems

  • Missing competences and capacities by flexible craft-oriented prefabricator to scale up their production to an industrialized one

  • Missing approaches for an iterative sustainability assessment of wooden buildings along the entire life-cycle

As a first step on this change, chapter two investigates on the current driver in the wood construction sector followed by a brief description on the current situation with regard to the interaction of planning and pre-manufacturing tasks in chapter three. Chapter four addresses the role of Building Information Modelling (BIM) as one possible enabler for a sustainable digital value chain and finally chapter five is summarizing specific requirements and fields of action.

2 Current Driver in Wood Construction Sector

The technical possibilities for prefabrication of wooden building systems have expanded greatly in recent years [4]. Most of these solutions are applied in the single-family house area. This is particularly due to the fact that here the element variants are limited and the prefabricators work with standardized superstructures and connections that are company specific developed and optimized. The guiding principles of prefabrication include the standardization of work steps, the systematization of process planning, and interdisciplinary cooperation between planners and those carrying out the work. According to the industrialization paradigms in construction developed by GRIMSCHEID, process orientation is one major pillar [5]. In the area of multi-story buildings, the potential is not fully exploited, since here the effort for planning and organization increases considerably with the number of element variants. In practice, the great design freedom of architects leads to individually developed superstructures and connections which, as project-specific detailed solutions, have virtually no repetition in prefabrication.

In general, industrialization requires interdisciplinary planning, as well as close cooperation between all involved planners, suppliers and executing companies, based on processes that link activities with defined follow-up relationships and with a continuous flow of information. The basic principle of individualized mass production is based on the intensive use of the most modern information and communication technologies in conjunction with modern manufacturing processes. The additional costs arising from customized production consist largely of information costs. The transmission of specifications to the production department, the increased complexity in production planning and control, coordination with the trades and suppliers involved in the prefabrication, as well as targeted distribution logistics are just a few indicators of the high and cost-intensive information and communication requirements. [6].

The core task of information technologies in the context of mass customization is to transfer the information about the specification of the customer’s requirements at the right time and in the right place. A promising approach lies in the integration of prefabrication and integral planning with extended BIM components (Building Information Model). In this way, the increasing demand for urban and affordable living space can be met with the necessary sustainability goals in product as well as in production [7]. The following chapter introduces the actual situation on that purpose.

3 Status Quo Analysis of the Value Chain

The aim of the status quo analysis (see Fig. 1) was to examine the value chain with regard to existing findings from relevant studies and projects in order to derive a concretization of the digitization level of the timber construction industry based on this. For this purpose, a structured research and interviews were conducted with stakeholders along the value chain. The findings of these investigations have been transferred into a value chain model. A comprehensive view of value creation can be taken by the value creation factors of product, organization, equipment, process and people [8]. An integrated mapping of the factors described can be achieved by using enterprise models. Therefore, a value chain model has been created using the Integrated Enterprise Modelling Method (IEM) [9].

Fig. 1.
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Pathway of investigation.

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In a next step further investigation on existing digital solutions, research projects and challenges and opportunities took place for the derivation of specific potentials and requirements.

3.1 Process and Digital Characteristics in Wood Construction

In contrast to conventional construction, timber construction based on prefabricated elements requires an earlier detailed examination of the construction process due to its higher degree of prefabrication. In the German-speaking countries, however, the strict separation of planning and execution is a major barrier. This is also reflected in the simplified value chain model (see Fig. 2).

Fig. 2.
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Status Quo of information exchange between planning and execution.

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Here, especially the vertical integration between the building design and planning of the prefabrication processes is still lacking. Approaches like leanWOOD [10] are addressing these challenges already and provide solution concepts for a more integrated planning process between the two disciplines. This way, the process can be shortened and the results optimized in terms of quality, deadlines and costs. Furthermore, an early involvement of prefabricators allows for a much more detailed consideration of company-specific solutions and supply chains, which can contribute to a better assessment and optimization of the sustainability of buildings in an early stage. Nevertheless, the implementation of the proposed approaches is still lacking.

When transferring the 2D or 3D CAD data of the architect’s design into the CAM planning of the prefabrication of the respective timber construction company, the company-specific conditions of the production processes installed there must also be considered. The CAM data are usually based on a 3D model and serves as the source for the machine control and tool selection of CNC systems. Production-relevant aspects such as material and energy consumption, static dimensioning, element pitches, etc. can be evaluated and optimized at this stage. Afterwards, all changes in the planning are associated with high effort in the execution or omitted planning services lead to a production repetition and thus to cost-intensive delays in the construction process. [11, 12].

A continuous computer-integrated manufacturing (CIM) chain of this kind has so far hardly been realized in the construction industry, with a few exceptions [13].

A further basis for industrial prefabrication is early and precise production and work scheduling. In most cases, work scheduling centers on a virtually modeled, three-dimensional building model, which is created with a CAD-CAM program. The planning data generated in this way can be used to obtain all the information required for production and converted into two-dimensional planning documents and individual part drawings. This also includes automatic generation of bills of material, machining programs and material requirements. [14, 15].

The additionally increased focus on ecological factors and its sustainability assessment, but also the desire for greater individualization is giving a significant boost to digital construction. This development calls for end-to-end information technologies for the designation of elementary data along the entire building life cycle.

4 The Role of BIM as an Enabler for Integration

With prefabrication, the systematization of detailed solutions is essential and inseparable from the early design phases. This necessity links modern timber construction with the BIM method, which describes a holistic approach of planning, execution and management of buildings with the help of consistent data availability. The basic idea is to digitally capture all relevant building data, link them together and, ideally, store them on a common data platform (see Fig. 3). [10, 12].

With the progressive further development and implementation of BIM along the entire value creation, the unidirectional exchange of information will be successively replaced [16]. Such a comprehensive and integrative value creation chain, in which all actors involved in planning and execution come together at an early stage of building development and explicitly align the results with the production process, corresponds to the so-called open-BIM model.

Fig. 3.
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BIM platform for information exchange.

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The results are brought together in a 3D model on a central data platform by means of a uniform data exchange format (e.g. Industry Foundation Classes (IFC)) and ideally linked to production-relevant data. Nevertheless, these solutions should be adaptable especially for small businesses with a hand-craft orientation. The provision of the necessary up-to-date production data represents a decisive step towards a digital integrated production. Automatic recognition of geometric properties by means of so-called “feature recognition tools” works for many standard machining operations, but is error-prone and not suitable for complex free forms. If the component geometry has been designed parametrically-associatively, this information must be made available to production via appropriate interfaces within the digital value creation chain. In timber construction, these are mainly CAM data formats such as “BTL” and “BVX”, which allow a machine-independent description of the geometry as well as information on machine processing. [12, 14, 17].

For this digital information flow with the integration of various data types from different stakeholders, completely in the sense of the Open-BIM approach, no suitable software is currently available. Research projects on the subject of data transfer in timber construction offer initial approaches to standardized and interdisciplinary data models. An example of the object-specific relationships of a component, in comprehensive data models, is the aggregation of information about:

  • Component (e.g. material, geometry, supplier, processing etc.),

  • Building (e.g. statistics, floor plans, energy management etc.),

  • Material (e.g. wood origin, carbon footprint, treatments etc.).

However, in order to make optimal use of the potential of the digital value creation chain and to harmonize the various data models across different product phases, the requirements for the interface exchange still have to be defined by the timber construction companies. In this respect, the BIM method shows parallels to the fundamental concept of a digital and continuous value creation chain. [17].

5 Conclusion on Potentials and Requirements

The potentials of an end-to-end information exchange within the timber construction industry in Berlin/Brandenburg can be proven in many places. In this context, the greatest possible effect can be achieved not only through the cooperation of the timber construction companies themselves, but rather through a vertical as well as horizontal digital value creation chain of the entire Berlin/Brandenburg value-added (timber) construction system. The accompanying integration of the Open BIM model supports efficiency, especially in the planning and preparation process, and opens up access to excellent process models. Thus, the industrialization of the prefabrication of the wood system components with an accompanying flexible automation is an essential lever for the sustainable establishment of the wood-based materials in multi-story residential construction in Berlin/Brandenburg. The development of regional and digital value creation chains requires networked action by all players. In order to be able to set up such value chains with trustworthy partners quickly and at low cost, common interoperable infrastructures for data exchange are a prerequisite for being able to use available data efficiently. The following table presents the main requirements in tabular form (Table 1).

Table 1. Digital value creation chain requirement table.
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With the methods of digitization, processes in the construction industry can be significantly optimized and new possibilities for individualization and traceability can be realized. For example, relevant data from prefabrication can be embedded in the end-to-end digital value chain of the wood system components and comprehensively evaluated in a life cycle analysis. The new and additional requirements for a forward-looking building culture can hardly be solved by other technologies, so that the circle to an overall ecological, economic and social sustainability is closed here.