Round-to-round composite joint design and manufacturing
High-performance timber composite joints for spatial round wood structures - Engineered to nature with force flow optimized design
Round timber, despite its excellent mechanical properties and low primary energy consumption, has been underutilized in construction due to challenges in drying behavior and connection technology. Traditional methods of connecting round timber, such as using steel plates or bolts, often result in significant slip and limited performance, especially in complex geometries. We have addressed these challenges by a significant change in thinking, how to connect round-to-round by means of developing cast joints that can be more easy designed and produced using CAD/CAM technologies and modern production tools like multi-axis milling of molds, grouting of using polymer concrete cast parts and 3D printing.
To describe the material behavior with/without composite action to wood as well as mechanical fasteners, various experimental investigations in the form of compression, tension, adhesion, embedding and bond strength tests have been carried out in recent years and corresponding numerical models have been calibrated. The insights gained regarding fracture and loss of strength behavior could be used for the modeling of cast form joints and applied to a roundwood bridge design as proof of concept. Geometry modeling has been done with Rhino(R) 3D with subsequent transfer of the geometry data into finite element analyses in ANSYS(R) for structural optimization and calculation with the composite material data. Challanges have been the description of a quasi-homogeneous and quasi-multilinear-isotropic situation with triaxial failure of the compound adhesively joint to an anisotropic natural material with defects, knots and moisture-dependent material behavior.
The intensive research and investigations over years lead into a significant number of results, achievements and built structures. Our innovative approach not only enhances the performance and durability of round timber structures but also opened up new possibilities for sustainable and efficient building practices.
Objectives
- Utilization of round timber more effectively in construction by new connection technologies,
- Cost-effective and efficient connection solutions using polymer concrete cast,
- Force-optimized design, appropriate to the materials.
- Accurately representing complex geometries and connections,
- Calibrating models based on experimental results and understanding the materials and structures,
- Building real structures based on engineering research and well don design.
Methods
- Numerical simulation the bonding behavior of polymer concrete cast parts,
- Evaluation of the interaction with the round timber under various load conditions,
- Advanced interface analysis addressing complex geometries and material properties,
- Model calibration based on the results of the experimental investigations,
- Experimental investigations on bonding of timber, from fracture mechanics to connection design.
Stats
Research team:
Prof. Dr. techn. Wieland Becker and team (1)
Prof. Dr.-Ing. Kay-Uwe Schober and team (2)
(1) Holzkompetenzzentrum Trier
(2) Hochschule Mainz, Forschungsgruppe Holz und Kunststoffe
Duration: October 2011 – March 2016
Budget: we want to keep that secret
Contact: Prof. Dr. Kay-Uwe Schober
Parts of the research were funded by the Rineland-Palatinate Ministry of Science, Further Education and Culture. Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the funding agency.
