Pilot project: A70 railway bridge

Ensuring notification of tendon failure following stress corrosion

The double-track line from Bamberg to Rottendorf travels underneath the A70 motorway at point "km 60.242". It was constructed circa 1968 using oblique two-span prestressed concrete with spans of 2 x 17.5 m = 35 m. The two separate superstructures are single-cell box girders. The prestressing steel used at the time, Sigma Oval 40 (St 145/160), exhibits a risk in terms of stress corrosion for the particular production period it was manufactured in. Because of the small quantities of reinforcing steel present in cross section, sufficient notification cannot be demonstrated by calculation, such that a sudden failure, without prior visible cracking, cannot be excluded.

The structure is therefore to be upgraded so that there is some notification of corrosion. It is to be performed by Josef Rädlinger Ingenieurbau GmbH in cooperation with Rädlinger Maschinen- und Anlagenbau GmbH, on behalf of the project manager, DB Netz AG Würzburg. (Technology Management DB: Tristan Mölter; planning: Prof Feix Ingenieure GmbH; testing: Dr Markus Hennecke). This is effected using steel plates which act as additional external flexural tension reinforcement. Using anchor bolts (TOGE TSM), the plates are firmly bonded to the cross section and anchored by connection to the abutment. The interaction of internal and external flexural tension reinforcement is ensured by the optimised stiffness of the composite anchor bolts and plates. In addition, the superstructure is shear-strengthened with vertically-integrated composite anchor bolts.


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