What is a hybrid timber structure?
Hybrid timber structures combine wood with steel to deliver innovative, sustainable structural solutions in place of all-steel construction to support factory conveyors, maintenance platforms, and other industrial equipment.
What is driving this change?
Manufacturers are actively transforming their supply chains to become more sustainable. This involves adopting practices from the circular economy, a system aimed at eliminating waste and the continual use of resources.
By incorporating innovative technologies and alternative materials, companies are working to reduce the ecological impacts of their products and manufacturing processes to comply with government regulations and meet consumer, investor, and employee expectations.
Introducing wood harvested using sustainable forestry practices can help reduce the overall environmental impact and offer a lower-carbon solution.
Case Study
Hybrid Timber Structures in Automotive Body-in-White Production at Volkswagen
Challenge
On a mission to reduce the environmental impact of their factories, Volkswagen asked the team at Valiant TMS in Austria to explore opportunities to integrate timber in a planned automated production system in Wolfsburg, Germany.
Following detailed analysis and concept development, which considered many factors, including functional, structural, and longevity requirements, a hybrid timber and steel design was selected as a sustainable alternative to all-steel construction for this application.
The pilot project included designing, fabricating, and installing the structure to support an overhead conveyor system that transfers rear floor sheet metal components from one robotic assembly cell to another.
Material Selection
In partnership with a local engineered timber supplier, cross-laminated timber (CLT) was selected for its dimensional stability and suitability for this hybrid application. The raw material is certified environmentally friendly and sourced from a forest in Austria under sustainable management.
Fire Resistance
Safety is a fundamental consideration when integrating any industrial automation system. Using wood to construct a load-bearing structure introduced elevated concerns related to fire protection. The structure had to meet or exceed the DIN EN ISO 19353-1:2018 standard criteria for machinery, which was confirmed through a classification report in accordance with DIN EN 13501.
The timber was treated with a fire-resistant coating consisting of a water-based, transparent fire protection primer and a thin-layered, breathable protective varnish to meet safety compliance. The coating creates a thermally insulating layer, which delays the spread of fire and reduces the development of smoke gases.
Design
The structure must support a 19-meter-long conveyor and its payload of parts, each weighing 21 kilograms. The engineering team considered two designs: a panel-based design using full sheets of high-strength plywood and a frame-based design primarily using timber beams and columns.
Engineers conducted a failure modes and effects analysis (FMEA) to evaluate each design; both options met strength and durability criteria. The frame-based design emerged as the better choice, offering greater flexibility for customization and improved visibility and accessibility for operators and maintenenace personnel, creating a safer and more efficient workplace.
Integrating different material types posed unique engineering challenges. Timber, concrete, and metal components needed to be connected, and each type of connection required a tailored approach to ensure structural integrity and durability.
Corrosion-resistant self-drilling rod anchors with hidden T-shaped and custom-angled plates connect the timber elements, such as beams, columns, and structural members.
Custom steel plates, brackets, and standard fasteners anchor the timber columns to the concrete floor and attach the metal conveyor components and other steel elements to the structure.
Results
The hybrid timber structure design phase consumed more time than typically required for a traditional steel structure primarily because of the necessary research and development. Despite the complexities, the structure was ready to be installed at the Volkswagen factory without disrupting overall project timing.
Having established the materials and joining techniques in this pilot project, the expected design time for future projects using similar hybrid timber structures should match those of traditional all-steel construction.
Highlights
- Lighter overall weight
- Faster to assemble
- Flexibility for customization
- Easier to recycle materials
- Reduced environmental impact through an estimated savings of 15,000 kg of CO2 when compared to all-steel construction
How much is 15,000 kg of CO2?
3.6 gas-powered passenger vehicles driven for one year 1
61,741 kilometers driven by a gas-powered vehicle 1
7.1 hectares of forests sequestering CO2 for one year 1
1 Source: https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator
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