Weiher and Zilch - Lehrstuhl für Massivbau

Weiher and Zilch 2008 CBC
comparison to bonded tendons and a higher demand of reinforcing steel the savings of prestressing
in this project did not lead to higher costs 31 . With this concept it is possible to
realise the pros pointed out before, without higher efforts. A durable and safe product can be
offered the owner. One has to bear in mind that the unbonded pt systems for internal use
differ in quality and suitability.
a)
c)
Fig. 6 a: cross section, arrangement of internal and external tendons at diaphragm
Fig. 6 b: longitudinal section, pt span 1 to 3
Fig. 6 b: detail of diaphragm, deviation and anchoring of external (red) and internal (blue) tendons
ROSSRIETHER GRABEN
Near Mellrichstadt (Bavaria) another pilot project with combined unbonded pt with external
and internal tendons has been realized (three span structure with single box - approaches 40m
each, inner span 50 m). As internal tendons a bundle tendon with wires in a duct has been
used 32,33 . They are arranged in the slabs like at the Mühlenberg Viaduct. In each span just one
concrete deviator has been placed. Also for this project there was no difference in the initial
costs compared to the use of bonded internal tendons 32 . The design has been done as to the
national code DIN 1045-1 25 and DIN Fachbericht 102 34 which are based on the Eurocodes 1
and 2. Within this project the exchange of the steel of an internal tendon has been shown to
check the feasibility 33 . The PE duct remained inside the structure. Transverse pressure
created friction and clamping between the wires also led to a high force necessary for
removal. Thus, the length and the deflections will be limited if the duct shall not be stressed
to seriously. After re-installation of the prestressing steel, the duct has been refilled with wax.
8
b)