Arabian Journal for Science and Engineering, Volume 37, Number 2, 2012
Cables of suspended structures are suffering due to increased corrosion and fatigue loading. Since 1980, EMPA and BBR Ltd. in Switzerland have been developing carbon fiber-reinforced polymer (CFRP) parallel wire bundles as cables for suspended structures. The excellent properties of those bundles include corrosion resistance, very high specific strength and stiffness, superior equivalent moduli and outstanding fatigue behavior. An anchoring scheme produced with gradient materials based upon ceramics and epoxy is described. For the first time, large CFRP cables were applied in 1996 on the vehicular cable-stayed Stork Bridge with 124 m span in Winterthur, Switzerland. The performance of these cables and later applications was and still is monitored with sophisticated fiber-optical systems. Up to date, these results are fully matching the high expectations. Under the assumptions that (1) the behavior of the pilot applications of CFRP cables described in this paper will be further on fully satisfactory, (2) active systems for distributed mitigation of wind-induced vibrations are going to be successful and (3) there is a need for extremely long-span bridges to cross straits like that of Bab el Mandeb, Messina, Taiwan or Gibraltar, why should the next generation of structural engineers not use CFRP cables for such extremely long-span bridges? This would open spectacular new opportunities.
The Stork Bridge, erected in 1996, is world’s first road bridge with Carbon Fiber Reinforced Polymer (CFRP) stays. It is situated over the 18 tracks of the railroad station in Winterthur, Switzerland. The CFRP cables used for the Stork Bridge consist each of 241 CFRP wires each with a diameter of 5 mm. The ultimate load of a cable is 12 MN. This cable type was subjected to a load three times greater than the permissible load of the bridge for more than 10 million load cycles. This corresponds to service life conditions several times greater than that which can be expected during the life cycle of the bridge. The cable-stayed Stork Bridge will certainly be a milestone in international bridge construction, because CFRP cables do not simply have excellent behavior with regard to corrosion and fatigue but are also five times lighter than steel cables with even higher strength properties. This high strength with low weight will permit to build in future bridges with considerably longer spans than are currently possible.
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