Crash barriers provide a crucial contribution towards safety in road traffic. In Germany, these are predominantly comprised of steel or reinforced concrete. In collaboration with project partners, we are developing a sustainable alternative: a crash-barrier system made from domestic wood species. It needs to be compatible with existing systems, just as durable and financially competitive.
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In an earlier research project at the Technische Universität Braunschweig, a crash-barrier system made from glass-fiber-reinforced wood was developed which is compatible with existing systems made from steel. Here, the focus was on the fundamental feasibility, which was successfully verified with the aid of a demonstrator.
The new project with the participation of the Fraunhofer WKI is the next step on the way to series production. It is to conclude with a prototype that fulfills all the substantiation required for utilization. The combination of unprotected weathering, durability and high mechanical and dynamic stresses is extremely demanding.
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All types of wood, reinforcing fibers and fasteners have specific advantages and disadvantages in terms of stability, durability, cost and environmental friendliness. For example, it is foreseeable that practically all types of wood will have to be treated with an effective wood preservative. The manner in which the protective measure is applied has, in turn, an influence on the further processability – in particular the bonding capability – and on the mechanical properties.
We will examine all materials and material combinations that appear to be expedient and will test their suitability by means of diverse investigations.
The total length of supra-local roads in Germany is around 230,000 kilometers (as of 2019). This includes highways, national roads, state roads and district roads. Crash barriers are not present everywhere, but the total length is nevertheless immense.
The crash-barrier systems used in Germany are made from bolted steel sections or prefabricated reinforced-concrete elements. The service life is assumed to be 25 years. This means that many kilometers of crash barriers are renewed every year. The production of crash barriers made from steel or reinforced concrete requires a large amount of energy and releases considerable quantities of carbon dioxide (CO2).
The deployment of wooden crash-barrier systems is an efficient means of improving the eco-balance of the construction sector. They can be manufactured using comparatively little energy and store CO2 for a long period of time.
From a global perspective, there are already a handful of systems which are made entirely or partially from wood. These have, however, various system-specific disadvantages, including a still-high steel proportion, the use of tropical hardwood, very elaborate construction, and incompatibility with established systems.
By developing a compatible crash-barrier system made from indigenous woods, we aim to create a consistently sustainable solution with high market potential.
For the German and European wood industries, a new market could emerge.
Contractors of crash-barrier systems (e.g. federal government, municipalities) could benefit from a broader choice of systems and an improved raw-material base.
Within the framework of the predecessor project at the Institute of Building Materials, Concrete Construction and Fire Safety (iBMB) of the TU Braunschweig, a crash test was carried out in order to demonstrate the fundamental feasibility. The wooden crash-barrier system passed the test. The impacting vehicle was stopped as desired.
© Fraunhofer WKI
© Fraunhofer WKI
Official project title: Development of a sustainable crash-barrier system made from highly stress-resistant wood-composite elements; Subproject 1: Coordination, experimental procedure and sustainability
Funding bodies: German Federal Ministry of Food and Agriculture (BMEL) and German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety (BMUV)
Project management: Fachagentur Nachwachsende Rohstoffe e. V. (FNR)
Funding reference: 2218WK46A3
Duration: 1.7.2021 to 30.6.2024
Fraunhofer Institute for Wood Research