FFU synthetic wood
FFU synthetic wood (from English Fiber Reinforced Foamed Urethane ) was developed in Japan in the 1970s.
The main area of application of FFU synthetic wood is the railroad, where it is used as a sleeper with a very long service life, high load capacity and resistance to liquids. In addition, FFU synthetic wood is used in construction in the area of sewage treatment plants , tunnel construction , anchor walls and in the area of hydraulic structures. In the field of railway technology, the sum of the bridge, switch and tunnel projects on which FFU synthetic wood sleepers were installed between 1985 and 2020 results in a track length of more than 1550 km, this on routes of light rail vehicles and track systems of the main railways with axle loads up to 36 t. It must be taken into account that the lengths of the individual projects (bridges, switches, tunnels) are in the range of 10 m to 500 m.
During this period, FFU synthetic wood sleepers were mainly used on the high-speed Shinkansen network and on regional railways and metros in Japan. FFU synthetic wood sleepers have been used in Europe since 2004. In 2019, around 20,000 railway sleepers were installed in Europe.
Development of the FFU
Records by Japanese railway operators in the 1970s showed that around 70% of their sleepers had to be replaced due to weathering.
The requirements of the railway companies for the technology of the newly developed railway sleeper were:
- same positive material properties
- easy handling and processing
- Use of the existing fasteners
- Higher life expectancy
- free from rot or decay due to the weather
- much higher weather resistance
- approximately the same specific weight
In cooperation with the Japanese railways, the Japanese plastics specialist Sekisui researched a material in the 1970s that met all of the above requirements. The newly developed material is called FFU (Fiber Reinforced Foamed Urethane).
historical development
In 1980, in cooperation with the "Railway Technical Research Institute" and the Japanese railways, two test tracks were equipped with Eslon Neo Lumber FFU.
In the Kanmon tunnel on the Sanyo main line, 74 FFU-BI blocks were installed in the slab track in the area of km 531 and 680 to km 531 and 700.
On the railway bridge over the Miomote River of the Uetsu route km 61 and 294 to km 61 and 316, 18 FFUs were used.
In 1985, after a trial period of five years, FFU from the above projects were expanded and examined. The test results showed no aging. The values were very good. FFU was introduced as a standard threshold at JNR.
In 1991 the Railway Technical Research Institute carried out further investigations on sleepers of the two test projects. The report indicated that there was no apparent aging of FFU. Other state and private railway companies started using FFU on their rail infrastructure.
In 1996 the Railway Technical Research Institute FFU expanded the above test routes and examined them again. In the course of these investigations, 100 million load changes were carried out on the removed sleepers. In theory, this means with 20 hours of rail operation per calendar day that approx. 275 axles roll over this threshold every hour. In other words, this corresponds to a practical load on a train with 28 axles every six minutes over a period of 50 years. The life expectancy of FFU was only hinted at because different railway operators have different train frequencies. In this test it was shown that the value for the bending stress of FFU is 100 million load changes.
In 2011, the RTRI carried out a test on sleepers from the first field tests in 1980. The FFU thresholds, which have been in use for 30 years, show a slight reduction in the technical parameters. As a result, the Railway Technical Research Institute is writing a letter to the Japanese Railways JR that these FFU synthetic wood sleepers can be safely used for the next two decades.
Use in rail networks
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Since 1985, after a practical test period of five years, FFU railway sleepers have been installed by the Japanese railways as a standard product in the field of bridges, switches and tunnels, both in the ballast bed and in the slab track .
- 2002 Use of FFU in the construction of the Shinkansen Kyushulinie and Tohokulinie.
- In 2004 it was installed for the first time in Europe by Wiener Linien at the Zollamtsbrücke.
- In 2005 it was used for the first time on the ÖBB network in Vienna.
- 2008 Installation of the first switch with FFU in Chempark Leverkusen.
- 2010 In spring, the Hamburger Hochbahnen equipped the first switch on their route network with FFU.
- 2011 Deutsche Bahn equips the first bridge in Vilsbiburg with FFU synthetic wood.
- 2012 Deutsche Bahn equips two points in Würzburg station with FFU. 70,000 tons roll over these points every day.
- Other European railway infrastructure companies use this type of sleeper especially on bridges and switches
- 2015 Tisseo (a local transport company) in Toulouse renovated 2 switches in slab track with FFU synthetic wood.
- 2020 Väylä tests FFU at minus 65 degrees Celsius and then carries out the first installation on bridges and routes.
literature
- Synthetic wood for track construction, Günther Koller. EI Railway Engineer April 2008
- Research report No. 2466 from September 19, 2008, Chair and Testing Office for Transportation Infrastructures Univ. Prof. Dr.-Ing. S. Freudenstein
- A material that sets the course. Clemens Bretschneider, Bodo Blume, Heinz Holschke, Thorsten Eschmeier, Alp Sarici. EI Railway Engineer March 2009
- Sleepers made of FFU synthetic wood in Europe, Günther Koller. FI Railway Engineer July 2009
- Brochure Eslon Neo Lumber FFU, SEKISUI
- RTRI research report - investigations after 30 years of use of FFU - in 2011
- Specialist article about the first use of FFU synthetic wood in the slab area - RTR special edition 2011
- Technical article about the first use of FFU synthetic wood at Deutsche Bahn - Railway engineer 1/2012
- Specialist article about the first use of FFU synthetic wood at Deutsche Bahn - Railway Gazette 1/2012
- Technical article about the first use of FFU synthetic wood - RTR 1/2012
