Wood in infrastructure construction
Infrastructure construction is one of the largest CO₂ emitters in Switzerland. The main cause is the use of reinforced concrete. By increasing the use of wood, infrastructure construction could contribute to decarbonization. The first good examples have been built. However, there is still great potential for development.
As early as 1998, Stefan Zöllig showed in a basic report that wood, as a domestic raw material, is a cost is a cost-effective and ecological alternative for wildlife bridges. About 20 years later, we are building such structures in wood. Wood is also successfully used for noise barriers and other infrastructure structures, wood is now successfully used. We are convinced that wood will be used as a standard be used as a standard in infrastructure construction.
Timbatec is involved in projects and at the political level, so that wood is used more in infrastructure more in the future. We believe that the political and new findings from research will bring about a breakthrough for wood as a building breakthrough in infrastructure.
Motion "Research and Innovation of wood as a material for use in infrastructure construction as a decarbonization contribution".
The Council of States and the National Council have approved themotion"Research and innovation of wood as a material for use in infrastructure construction as a decarbonization contribution". The Federal Council is now tasked with universities and the relevant standardization commissions to investigate the possibilities for decarbonizing infrastructure construction. In particular, it is to be examined or sought to supplement or replace reinforced concrete with CO₂-storing materials. The research and innovation of wood as a material for widespread use in infrastructure construction is in the foreground.
Wood as a CO₂ store - also in infrastructure construction?
Concrete is by far the most the most frequently used building material. In Switzerland, we use around 40 million tons of it every year. This has a major impact on the climate. Alone With annual CO₂ emissions of around 2.5 million tons, cement production alone accounts for over 5 percent of national CO₂ emissions.
Wood, on the other hand, is a CO₂ store. One cubic meter of wood relieves the atmosphere of about one ton of CO₂, because trees convert CO₂ into oxygen and CO₂ during growth thanks to photosynthesis.
trees convert CO₂ into oxygen and carbon through photosynthesis.
carbon.
Every cubic meter of timber contains thus stores around one ton of CO₂. is stored. Wooden buildings thus become long-term CO₂ stores, because the CO₂ remains stored in the wood until it is burned or rots. Then exactly the same amount of CO₂ is released back into the air as was once stored during the growth of the wood. was stored. If the wood is reused, the CO₂ remains stored during a further life cycle. stored during a further life cycle.
Research and implementation strategy with the Bern University of Applied Sciences
Timbatec has developed a research and Bern University of Applied Sciences to develop a research and implementation strategy. We identified nine areas where wood could be increasingly used in the future. could be used. For the construction of infrastructures, in the building sector, but also in other areas, such as the road sector, there are already various solutions with various solutions are already available with materials that do not produce CO₂ during production, but rather store it, such as wood. Wildlife overpasses, noise barriers or cross-axis bridges are already being built in wood. timber construction.
So that wood could once be used in tunnel construction projects and heavy-duty bridges, various research questions still need to be clarified. research questions still need to be clarified. We are in close contact with the leading leading universities.
The research and implementation strategy of the Bern University of Applied Sciences, on the possible areas where in the future wood can be used and thus substitute steel and concrete. The resulting amount of CO₂ saved makes a significant contribution to climate protection.
Will we be building bridges for 40-ton trucks out of wood in the future?
A great potential for the
The use of wood in infrastructure construction lies in the bridge sector, in particular for
bridges over freeways. The almost 2255-kilometer-long national road network in
of national roads in Switzerland comprises 4270 bridges - that's about two bridges per
kilometer of road. Most of these are made of steel and concrete. Wood
is currently used in only around three percent of the load-bearing structure. Yet
versatile material has great potential, including for the construction of bridges
for large loads such as 40-ton trucks.
Researchers from the Institute for Wood Construction, Structures and Architecture IHTA of the Bern University of Applied Sciences BFH are working together with partners from the industry, are working on a feasibility study on how heavy-load bridges be built with wood as standard. Timbatec is strongly project, because we are convinced that such bridges can be realized soon. soon be realized.
Working model of the feasibility study
The bridge elements shown are planned for a cross-axis bridge. planned. Thus, for example, a cantonal road over a 6-lane highway with one center support (2 x 22.5 meters span as a two span girder and 40 tons payload).
The individual bridge elements are around three meters long and consist of a hollow box cross-section of cross-laminated timber panels. The TS3 technology connects the individual bridge elements to each other in a flexurally rigid manner, which increases the torsional stiffness and the individual panels act efficiently. increases torsional stiffness and the individual panels interact efficiently. together.
The bridge elements are a working model that allows the current details to be evaluated more directly in order to to try out new solutions in the ongoing research project.
WHFF Project 2021.15
- Duration: January 2022 to July 2023
- Funding agency: Federal Office for the Environment,
- Forest and Wood Research Promotion WHFF
- Funding amount: CHF 107'945.-
- Project management: BFH, Prof. Dr. Steffen Franke
- Main implementation partners: TS3, Timbatec, VSL SA
Further information about the projectwww.bfh.ch/ahb
An important milestone in the development of the TS3 technology was the long-term test stand in the courtyard of the BFH in Biel. It was officially inaugurated in May 2018 and dismantled three years later, as the necessary knowledge had been gained. In the spirit of the circular economy, the cross-laminated timber from the long-term test stand was reused for the construction of the bridge elements.
Working model of heavy duty wooden bridge inaugurated
hbs holzBaumarktSchweiz, Issue No. 4/2022 – Will we build large infrastructure structures such as highway bridges from wood in the future? Through the increased use of wood, infrastructure construction could contribute to decarbonization. Heavy-duty bridges with prestressed box girder elements would make large structures such as highway bridges and viaducts possible. A working model of this has been on display in Biel since May 9. (Report in German)
Highway bridges – made of wood?!
Wir Holzbauer, Issue 5.2022 - For timber engineer Stefan Zöllig, timber construction should continue to gain momentum - carried by research projects such as the heavy load bridge made of wood. His latest project was presented and inaugurated in early May at the fourth International Timber Bridge Conference ICTB on the campus of BFH Biel with a first bridge model. (Report in German)
The CO₂ savings would be great
Bieler Tagblatt, Issue No. 10.05.2022 – Timber construction: Can bridges for heavy traffic also be built from wood? This question is being investigated by a research consortium at Bern University of Applied Science. A ten-meter-long working model was presented yesterday in Biel. (Report in German)
Wooden bridges for the next generation of infrastructure routes
VSS, Special Edition Wooden Bridges, Issue No. 7-8/2022 – Wood as a material and its wide range of products and technologies can be used not only for bridges for low-speed traffic, but also offer the potential for heavy-load traffic. Newly, long-span wooden bridges with a box girder cross-section and prestressing are to be used for heavy goods traffic. For a climate-neutral Switzerland 2050, answers from research and development are needed to show the construction industry new, efficient and climate-neutral solutions. (Report in German and French)
After wildlife overpass comes wooden highway bridge
Holz-Zentralblatt, Issue No. 26/2022 – Infrastructure construction is one of the largest Co₂ emitters in Switzerland. The main cause is the use of reinforced concrete. Through the increased use of wood, infrastructure construction could contribute to decarbonization. Heavy-duty bridges with prestressed wooden box girder elements could also enable large structures such as highway bridges and viaducts. (Report in German)
What are the limits for bridges made of wood?
The limits are in the head. Wood can do almost anything today that steel and concrete can do. Particularly efficient are particularly efficient for spans of up to 30 meters, i.e. exactly the range that most most Swiss bridges span. The possible uses of wood in bridge bridge construction go far beyond the usual spans.
As early as 2005, Timbatec, together with Zbinden AG, the Bauart architects and the Graz University of Technology. University of Graz, Timbatec developed a timber variant for the 240-meter long long bridge over the River Inn at Vulpera in the Lower Engadine. The concept is based on four hollow box arches running side by side.
A working model of the 240 meter long wooden bridge Vulpera with an arch span of 120 meters and a height of 70 meters.
Foresight is required
Unfortunately, the project could not not win the favor of the jury. The planning of the Inn bridge has, of course, fulfilled all the requirements. However, the jury saw a "transgression of the limits of the material design" - a disappointment for the team. All technical prerequisites for large-scale projects such as the Vulpera Inn Bridge are in place today. The only thing missing is the broad acceptance and the foresight of the decision-makers. New ideas sometimes have to wait a long time wait a long time.
Built infrastructure projects from wood
Wood
is already being used today in various infrastructure structures.
Noise barriers along train lines, highways and major roads
and major roads shield against disturbing noise. Wildlife bridges enable deer and
deer to cross such roads. And wooden bridges have been
have been around for hundreds of years. We present successful infrastructure
presented.
Wildlife bridge Rynetel
Switzerland's first wildlife bridge made of wood
When the deer cross the A1 highway to mate this summer, they won't notice that they're walking across Switzerland's first wooden wildlife bridge. For them, it is important that their territories beyond the motorway are made accessible again. Because traffic routes cut through the habitats of wild animals, the Federal Office for the Environment defines wildlife corridors of supraregional importance. Conventional wildlife bridges are reinforced concrete structures. They serve the animals, but are anything but climate-friendly. The two environmental aspects can certainly be combined: The "AG6" corridor connects the Jura region with the Mittelland and runs between Gränichen and Suhr over the A1. Here, the 50-meter-wide wooden construction now enables wildlife to cross the highway safely.
Swiss wood
Hüsser Holzleimbau AG in Bremgarten processed around 850 cubic meters of construction timber to manufacture the 156 arched girders. A large glue press pressed the spruce boards into the desired shape until they were dimensionally stable after the RF adhesive had cured.
Over 1000 tons of CO₂ saved
One cubic meter of wood relieves the atmosphere of around one ton of CO₂, because trees convert CO₂ into oxygen and carbon as they grow thanks to photosynthesis. The production of one cubic meter of reinforced concrete, on the other hand, generates around 500 kilograms of CO₂. The construction of the wildlife bridge superstructure in concrete would have caused emissions of 480 metric tons of CO₂ during manufacture, assembly and transport. With the timber variant, only 182 tons of CO₂ were emitted during the production of the glulam and for the manufacture of the steel joints.
At the same time, the wood used stores 775 tons of CO₂ thanks to photosynthesis. Net, 565 tons of CO₂ are stored in the Rynetel wildlife bridge. The difference between the wooden and concrete variants is therefore 1073 tons of CO₂. This corresponds to the emissions of over three million car kilometers. Wood is thus clearly ahead on the climate issue. If we want to achieve the Paris climate targets, we have to do without steel and concrete. The Wild Animal Bridge with its wooden superstructure is a first step in this direction.
Comparison of greenhouse gas emissions of the timber overburden with a concrete overburden. The overpass structure without foundations and without foundations and without superstructures on the basis of the preliminary project.Calculation according to KBOB 2009/1:2022, The concrete cover was calculated according to the preliminary project with a cross-sectional area of 28.64m. The concrete cover was calculated according to the preliminary project with a cross-sectional area of 28.64m² and an average length of 73.19m, thickness at the apex 40cm. This results in 2400t concrete and 144t reinforcing steel. The timber cover was calculated as realized with 382t glulam and 54t steel joints.
Construction
and assembly
The 850 cubic meters of timber for the wildlife overpass in Suhr grew in the Swiss forest within and offcuts, within 3 hours and 26 minutes. 26 minutes. From this, 156 glulam arches were prefabricated and glued in a dimensionally stable manner.
The girders, each weighing two tons, have a span of 17.4 meters, a cross-section of 24 by 76 centimeters and are mounted on the cast-in-place concrete walls with steel joints.
In the the construction is covered with 70 centimeters of soil and seepage gravel, at the outer walls and the outer walls and the middle layer (right in the picture) the earth layer is over 4 meters high!
A two-meter high glare shield delimits the bridge. On the side of the bridge, the the bridge, the glare shield is connected to the wildlife fence to prevent animals from the highway. The glare shield is an important element, which protects against from headlights, so that the animals can cross the bridge as undisturbed as possible. the bridge as possible.
The installation of the girders was carried out exclusively in night work. During 24 nights from 9:30 p.m. to 5 a.m., traffic was reduced to one lane in each direction and merged into one lane. This meant that work could be carried out over the other lane in each case. A total closure of the highway was ruled out from the outset.
Wood is the better solution
In the preliminary project phase of the Rynetel wildlife bridge, the client, together with the planning team, compared the designs in concrete and wood. In addition to cost-effectiveness, the structure had to be low-maintenance and durable and last for 100 years. A later expansion of the highway from two to three lanes must be possible, and the flow of traffic on the highway must be able to be guaranteed at all times during the construction period. These requirements are no problem for wood.
Construction data
- Spans: 2 x 17.4 meters
- Length: 35.6 meters (transverse to the roadway)
- Width: 54 meters (longitudinal to the roadway)
- Bridge area: 1'922 m²
- Timber: 850 m³ spruce
- Origin Switzerland
Construction costs
- 13.9 million Swiss francs
Services Timbatec
- SIA Phase 31 Preliminary design
- SIA Phase 32 Construction design
- SIA Phase 41 Tendering and comparison of offers
- SIA Phase 51 Detailed design
- SIA Phase 52 Execution
- SIA Phase 53 Commissioning
- Technical planning fire protection
Client
Federal Roads Office ASTRA
4800 Zofingen
Holzbau
Häring AG
5074 Eiken
Photography
NILS SANDMEIER
2501 Biel/Bienne
Planning
Ingenieurgemeinschaft WUEF;
Bänziger Partner AG, 5400 Baden and
Timbatec Holzbauingenieure
Master builder
Aravia Bau AG
5303 Würenlingen
Glulam supplier
Hüsser Leimbau AG
5620 Bremgarten
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Wildlife bridge Neuenkirch
Wildlife bridge from local wood
In Neuenkirch, the the Federal Roads Office (FEDRO) built the second wildlife overpass with a wooden second wildlife overpass with a wooden cover. As with the structure in in Rynetel, the assembly work in Neuenkirch also had to be carried out at night. had to be carried out at night. During ten nights, carpenters assembled the 17.5-meter-long, 1.24-meter-high and 1.24 meters high and weighing 8 tons.
Around 2500 cubic meters of mainly spruce wood from the Entlebuch from the Entlebuch region were used. The fact that the wood was forests and processed in regional companies is a benefit for the local economy. for the local economy. The environment is also pleased. Because local wood is significantly more advantageous from an ecological point of view than wood from abroad.
Construction and assembly
Also in Neuenkirch the bridge was erected completely in night work to ensure that the highway erected at night. For 21 nights, the police diverted traffic to the opposite lane of the highway so that the lanes below the overpass could be used for the assembly work. could be used for the assembly work.
Compared to the Rynetel flyover, the costly steel components could be steel components could be greatly reduced. On top of the abutments and the central wall oak sleepers (yellow) and horizontal contact timbers, also made of oak, to support the oak, for supporting the 17-meter-long and 8-ton spruce girders. spruce girders.
The beams made of glulam GL24k are designed as single-span beams with a cant of 10 centimeters. They have dimensions of 720 x 1240 millimeters and are arranged at a skip dimension of around 1.15 meters. The secondary supporting structure consists of 100-millimeter-thick cross laminated timber panels that are fastened directly to the longitudinal girders and serve as a base for the multilayer waterproofing.
The structure in Neuenkirch also has several layers of several layers for impermeability and root protection cover the timber structure. Unlike the Rynetel viaduct, the portals could be built without an embankment. without embankment. The anti-glare protection was directly included in the portal design. and mounted on the parapet.
Anyone traveling on the A2 between Sursee and Lucerne today pass the wildlife bridge immediately after the Neuenkirch motorway Neuenkirch freeway service area - often without realizing the materials with which materials the bridge is constructed of.
Construction data
- Width 50 meters
- Length 36 meters
- Clearance height 4.80 meters
- 2500 m³ spruce wood from the region
Construction costs
- BKP 1-9: 10.7 million Swiss francs
- BKP 214: approx. 2.7 million Swiss francs
- Planning fee: 198,000 Swiss francs (as sub-planner of the civil engineer)
Services Timbatec
- SIA phase 31 preliminary project
- SIA phase 32 construction project
- SIA phase 41 invitation to tender and comparison of offers
- SIA phase 51 execution project
- SIA phase 52 execution
- SIA phase 53 commissioning
- structural analysis and design
- cost estimate
- technical site supervision and site inspections
Owner
Federal Roads Office ASTRA
4800 Zofingen
Timber constructionengineer
Timbatec Holzbauingenieure (Schweiz) AG Bern
3012 Bern
Timberconstruction
HUSNER AG Holzbau
5070 Frick
Civil engineer
IG 2B Ingenieurgemeinschaft
3000 Bern 15
GU/TU
Anliker AG
6021 Emmenbrücke
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We are convinced that wood as a material will find its way into infrastructure construction because it is the most environmentally friendly option. That is why we are constantly developing new construction solutions with our partners, calculating the statics and ensuring the fire protection of infrastructure buildings. Anyone who wants to make a contribution to climate protection today builds with wood - also in the infrastructure sector.