The ReSidual research project aims to use digital construction technologies to make more economical use of wood as a resource in the construction industry. Waste material from the production of timber components is to be joined into load-carrying components using artificial intelligence and robotic production methods. A further reduction in the amount of wood required is to be achieved by combining it with earth. In the cooperation project between KIT Digital Design and Fabrication (DDF), KIT Timber Structures and Building Construction and the industry partner GROPYIUS, the necessary AI-based planning and robotic manufacturing processes, single-variety joining techniques and the material composite between earth and timber are to be researched. In addition to the use of residual wood in the factory investigated in the project, there are also links to the processing of residual wood and thus considerable transfer potential for realising secondary material cycles in timber structures using digital construction technology.

Contact: Simon Aurand and Daniel Fischer (DDF)

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As part of the project, the use of production-relevant data is being promoted. Examples from the timber industry will be used to show how the intelligent and sovereign use of data can succeed in a federative ecosystem. In addition, methods and services for addressing key challenges will be developed and made available. The intention is to realize and document demonstrators, further develop and apply big data technologies, co-design and apply guidelines and standards, build skills and capacities and promote exchange between stakeholders. champi4.0ns demonstrates the added value of using data in the fields of traceability, planning and control and quality assurance in the timber industry and beyond.

Project website: https://www.champi40ns.eu/

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In view of the increased threat to spruce stocks due to climate change, wood-based materials made from alternative wood species will be needed in the construction industry in the medium term. The aim of this project is therefore to develop load-bearing construction products made from the wood of the fast-growing and drought-resistant bluebell tree (also known as Kiri or Paulownia spp.) and to facilitate their development and introduction. However, since kiri wood is significantly lighter than spruce wood and has different mechanical and anatomical properties, it is first necessary to create a basic database in order to be able to successfully carry out strength grading of boards made from kiri wood. In a second step, these boards are to be used homogeneously and combined with spruce wood in timber products such as glulam or cross laminated timber and investigated.

Contact: Alexander Weese

In private house construction, cross laminated timber panels are used for ceilings and walls in addition to timber panel construction. Cross laminated timber has a very high weight, which is primarily due to the high amount of wood used in the cross laminated timber elements. For this reason, the development of a diagonal laminated timber lightweight wall is planned as part of the development project. This makes it possible to achieve a considerable weight saving of up to 40% by profiling the internal board layers to meet specific requirements. By arranging some layers diagonally, mechanical properties can be achieved that are equal to or higher than those of cross-laminated timber panels. The additional air inclusion through the profiling also ensures a higher thermal insulation value with corresponding diffusion openness.

Contact: Stephan Strübel and Kay Ackermann

In hardwood connections with dowel-type fasteners subjected to lateral loading, the high bulk density leads to high load-carrying capacities and has an influence on the load-carrying behavior. Material properties and system parameters such embedment strength, pull-out and head pull-through strength influence the joint behavior and also the failure modes. Failure of the fastener cross-sections can be observed more frequently due to the higher stress in hardwoods. When subjected to lateral loading, the fasteners exhibit a multiaxial stress state, as bending moments, shear forces and normal forces can act simultaneously. Depending on the type and geometry of the fastener, these vary and can lead to a shear or tensile failure of the fastener as part of an interaction of internal forces. The investigation of the new type of failure aims at a comprehensive understanding and full utilization of the connections.

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Position imperfections of self-drilling wood screws are characterized by deviations between the planned and actual screw channel. They occur unintentionally during self-drilling screw insertion and increase with increasing screw-in length. With long, slender screws, positional imperfections are insufficiently compensated for by minimum distances. Within crossed arrangements, this can lead to contact or collisions between screws. Possible consequences are thread damage, plastic deformation or even twisting or breaking of the screws. This affects the mechanical effectiveness of a screw connection and reduces its load-carrying capacity and durability. The IGF research project involves investigating the causes of positional imperfections and the damage mechanisms. The aim is to develop models to describe positional imperfections and to formulate practicable solutions to avoid contact and collision-related problems in screwed connections.

Contact: Eva Baldauf

Lövträ is a cooperative research project of Linné University in Sweden with the participation of KIT. The subject is the investigation of the material behavior of hardwoods. Due to their increased mechanical properties compared to softwood, this type of wood allows a reduction in the required cross-sectional dimensions and is suitable for reinforcing softwood products. In addition to being used for reinforcement for compression perpendicular to grain stresses, transverse layers of hardwood in cross laminated timber are conceivable for increasing the rolling shear strength, for example. However, little is known about the long-term behavior of hardwoods and the influence of different climates. In order to close this gap, tests are being carried out under various climatic conditions. The focus is on the compression perpendicular to the grain, rolling shear and embedment strength. The test program includes both short-term and long-term tests. Southern Swedish beech and birch timber as well as spruce are tested as a reference. The results are intended to support the usability of hardwoods in the construction industry.

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A guideline with recommendations for the reuse of timber and steel construction products was developed in collaboration with the Technical University of Munich and KIT Steel and Lightweight Structures. It shows ways and means of reclassifying components realised during dismantling so that they can be reused as load-bearing components in line with the circular economy. The main focus is on softwood lumber, glulam, OSB panels, I and H profiles made of structural steel as well as trapezoidal sheet metal and sandwich elements. Inspections of deconstruction objects and observations of deconstruction processes and structural conditions were key elements of the field research to ensure that the results for the guideline are in line with the "reality of deconstruction" and are adapted to the expected structural conditions.

Contact: Matthias Frese

Practical guide: Guide to the reuse of load-bearing components (PDF in German)

Research report: Preparation for the reuse of certain timber and steel construction products (in German)

Positive and negative experiences with the durability of installed timber have shown that successful preventative structural measures are a guarantee for the long-term durability of installed timber. Such measures ensure that the wood is either always dry or almost always dry due to the potential for re-drying. On behalf of the Ministry of Regional Development and Housing BW, construction principles, guiding details and recommendations for preventive structural timber protection were developed, which are to be incorporated into DIN 68800-2 Timber protection - Preventive structural measures in building construction. Their observance during design, planning, execution and maintenance should contribute to the long-term durability of timber structures.

Contact: Matthias Frese

Final report: Karlsruhe Reports on Timber Engineering, Volume 41

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New development of a hybrid construction method through the advantageous combination of the materials steel and timber for linear load-carrying elements subject to bending load. The hybrid construction method is characterized by the shear-resistant embedding of a high-strength steel profile in a compact timber cross-section. This allows the specific advantages of the two building materials to be optimally utilized and the weaknesses of the building materials to be compensated for by the composite partner.

Contact: Simon Aurand and Peter Haase

Development of integrated timber-steel hybrid elements for commercial and multi-storey buildings with spans of up to 10 m and development of a suitable design concept.

Contact: Stephan Strübel

Final report sub-project 1

Final report sub-project 2

Development of economical, reliable and innovative joining technologies for hardwood components and corresponding design rules.

Contact: 

Final report in the FNR project database

Development of a truss girder concept for spans of up to 100 m using laminated beech veneer lumber, hybrid beams made of softwood and beech wood, and wood screws as fasteners.

Contact: Sebastian Egner

Final report sub-project 1

Final report sub-project 2

For the first time, new connectors made of densified veneer wood (DVW) were realized. Initially, the surface of the DVW was treated to increase the friction between the connector and the timber component in the shear joints and thus significantly increase the load-bearing capacity of the connection. Friction tests were carried out to determine the friction coefficients of the surfaces. In subsequent compression-shear tests, the behavior of the surfaces in connections with inclined fully threaded screws was investigated.

Contact: Simon Aurand

Final report: Karlsruhe Reports on Timber Engineering, Volume 38

Laminated Segment Timber (LST) consists of mutually glued trapezoidal lamellas made of Spruce. Due to the optimization of process parameters the wood yield can be increased to an average of 85%. LST and layered LST are regulated in ETA-19/0832. Simulation studies deal with the characteristic bending strength at variing member depth and height as well as modifications in the production process.

Contact: Lukas Windeck

Final report: Karlsruhe Reports on Timber Engineering, Volume 37