On behalf of the Karlsruhe Regional Council, the PORR Ingenieurbau team is constructing a 667-meter-long high-level bridge that will span the Neckar Valley in the future. The current focus is on constructing the superstructure—a phase that requires the highest precision and seamless coordination among all trades.

Cable-stayed cables as the load-bearing backbone

At axes 30, 40, and 50, the superstructure is suspended using five cable-stayed cables per girder. The cables are arranged in a so-called harp shape and play a crucial role in the bridge’s load-bearing capacity. The Horb Viaduct is designed as an extradosed bridge: a construction method that combines elements of classic prestressed concrete construction with those of a cable-stayed bridge.

Modern strand bundle cable systems are used: Each anchorage consists of 108 high-strength prestressing steel strands. The stay cables run at an angle of approximately 18 degrees to the horizontal and are attached to the bridge’s pylons.

Precision work during the construction of the pylons

The prerequisites for the current cable installation were already established during the pylon manufacturing phase. So-called anchor boxes were cast into the pylon sections. Via the head bolt anchors arranged on the outside of the anchor boxes, they are force-fit connected to the concrete cross-section and later safely transfer the enormous forces into the supporting structure.

Precision work is also required on the underside of the main girders: pilasters for the subsequent cable anchoring were cast into the concrete there. Construction in these specific areas was particularly challenging. The extremely high reinforcement density in the reinforced concrete left little room for maneuver. Meticulous placement of the reinforcement was essential to ensure the precise installation of the cable anchorage components.

Technology designed for the long term

The stay cables used consist of waxed and PE-coated tension steel strands that are drawn into an HDPE sheath, which protects the cables from environmental influences. The individual strand bundles are anchored by wedging them into the fixed anchor on the pylon.

The cables are tensioned exclusively via tensioning anchors mounted beneath the superstructure, behind the pilasters, and the process is carried out in several precisely defined tensioning stages.

Once the tensioning work is complete, the strand ends are trimmed, treated with corrosion protection, and finally covered with a shared protective cap, which contributes to the structure’s durability.

Next Milestones in Sight

The substructures of the high bridge have already been fully completed. With the start of cable installation, another key milestone has now been reached. The coming construction phases will involve further challenging steps: the shifting of the support scaffold, the hoisting of additional heavy-gauge steel plates, and the construction of the second and third cable sections.

With each new cable, the Horb Viaduct continues to take shape and visibly grows into the structure that will define the Neckar Valley in the future.