Strengthening of 3 railway bridges with post-tensioned CFRP tendons – ?trbské Pleso, Slovakia

Project

Along the 4.75 km-long section of the Ko?icko-bohumínská railway are three bridges that were built in the 1960s and have been in use ever since. The structures comprise five precast post-tensioned concrete box girders across three spans.

At the end of 2020, the bridges were reassessed for the new loads of the heavier trains. The analysis showed that the stress limit in the serviceability limit state (SLS), according to Eurocode EN 1992-2, was exceeded because of the tensile stresses in the lower part of the cross-section.

Since an additional compression force was needed, it was quickly determined that the girders would have to be externally post-tensioned.

Solution

As the distances between the existing prestressing tendons in the girders are between 45 mm and 95mm, no standard anchorage could be used. In addition, the box girders at the thinnest point have a concrete thickness of only 120 mm.

To introduce the force of the 90 CarboStress? systems without damaging the existing prestressing two project specific anchorages where designed.

One consisting of two shear dowels and the other one which was used where the distance is only 45 mm between the existing tendons consists of 14 chemical bolts to transfer the tensioning force of the CFRP plate into the bottom of the girders.

CarboStress? offeres great flexibility to design new anchorages which allows to apply the additional post-stressing force without damaging the existing prestressing cables, a low weight of the CFRP tendons so that they can be installed by hand and therefore do not require any road closure, and years of experience in the field of bridge reinforcement. Thanks to these and many other characteristics, an optimal and cost-efficient reinforcement solution could be realized.

Facts

Object: ?????????????????????????Railway bridge strengthening, 1st stage

Location: ???????????????????????trbské Pleso, Slovakia

Retrofit year: ??????????????? July 2021 (3 weeks)

Strengthening system:?StressHead-CarboStress?

Quantity of system: ??????90 pieces

Length of tendon: ?????????10.00 – 16.00 m

Involved parties

Owner: ???????????????????????????SR – Railways of the Slovak Republic

Contractor: ?????????????????????SR – Railways of the Slovak Republic

Engineer: ??????????????????????University of ?ilina