Bonded Steel Plates for the Reduction of Fatigue Stresses of Coupled Tendons in Multispan Bridges

The working joints of many span-wise built p/c-bridges are cracked. Thereby, the fatigue stresses in the prestressing steel at the joints, where all tendons were coupled, increase markedly. To prevent premature fatigue failure, strengthening of the joints became necessary.The injection of cracks has not proved to be a sufficient countermeasure for all bridges. The fatigue stresses can be reliably reduced by additional steel plates bonded to concrete with suitable epoxy resin adhesives. The first successful application of this strengthening method was carried out on an Autobahn-bridge near Dortmund in 1981. Its efficacy was proved by load tests. Other bridges followed. The use of fibre composite plates instead of steel plates is also tested. The rules for the dimensioning and bonding of the plates and for accelerated durability tests of bonded joints are presented.