Kander Viaduct, Switzerland

Case Study Description

Built in 1911 in Frutigen on the mountain ridge of the Lötschberg, the Kander Viaduct is a landmark of the valley and the most photographed bridge of the region. This bridge of stone masonry with a total length of 899 ft (274 m) has been used as an important passenger and freight railway connection between northern and southern Europe for over 100 years.

As part of the regular building inspections, it was found that the polymer bitumen sealant (PBS) installed 60 years ago no longer protected the structure against ingress of water, which had started cause damage to the structure. To ensure the integrity of the bridge over the coming decades, a new protection-system was required. The engineering firm commissioned with this project offered an additional ultra-high performance fiber reinforced concrete (UHPC) variant that took into account the structural and waterproofing properties of this material as well as extensive time savings for the construction.

Special Features

As this project was the first of its kind for the client, the variants were extensively studied to compare their respective added value. In the end, they decided to use the UHPC variant due to its extensive time and life cycle cost reduction.

The extremely dense matrix of the UHPC ensures that the layer poured on the bridge at a thickness of only 1 inch (3 cm) is completely waterproof. The condition of the old concrete overlay was significantly worse than expected. However, thanks to the UHPC solution, and in particular by applying the entire horizontal area on a single day, work has been completed on time and budget. Through this one step installation process, joints in the area of the water drains could also be avoided.