Innovative Approach

Complete renovation and redesign of the nearly 550 m long section are being undertaken. The operational improvements of the heavily trafficked road include the construction of a concrete roundabout located beneath the SBB bridge. To achieve the necessary clearance height under the SBB bridge as per standards, the existing track bed will be lowered. The current SBB bridge B-223 will be replaced on-site with a new construction featuring a wider span.

The new reinforced concrete bridge, which showcases new, geometrically sophisticated pillars and abutments, will be encircled by a concrete roundabout. The prestressed bridge deck will be prefabricated on-site near its final location on a falsework. Subsequently, the bridge deck, along with the falsework, will be moved 26 m longitudinally and 12 m laterally into the correct position during a weekend operation. Additionally, a steel cycle path bridge will be attached to the bridge, ensuring a connection across Mellingerstrasse for slow traffic.

Moreover, this technically ambitious and extensive project includes adjustments to the track bed including utility lines, surfacing work, and various structures. To minimize disruptions to rail operations, various night-time works and a 9-week closure of the SBB track were necessary.

Challenges of the Project

• Schedule/Construction Time: The complete demolition and reconstruction of the SBB bridge on Mellingerstrasse will be realized in about 7 weeks. The road and utility line works, as well as various retaining walls, will be completed over approximately 2 years until the end of 2023.
• Work above or directly next to road traffic (Requirement: Road always dual-lane accessible with DTV > 24’500)
• Detailed coordination of individual construction phases with available track closures by SBB.
• Technically highly demanding bridge construction work (lateral prefabrication of a prestressed concrete slab, demolition of the existing bridge, new construction of pillars and abutments, falsework assembly for bridge shifting, steel walkway assembly on the side of the bridge for pedestrians and cyclists, etc.)
• Technically very complex in-situ and shotcrete work (two-layer roundabout construction, demolition and reconstruction of retaining walls, execution of building underpinning, creation of nailing walls, etc.)
• Linear construction site: Extensive earthwork, utility, and road construction work (roadway lowering, new construction of sidewalks, creation of tree pits, excavation work for district heating/cooling, water and natural gas pipelines, etc.)
• Limited space conditions: always dual-lane accessible with DTV > 24’500 / Access / Logistics of the construction areas, etc.
• The project was able to be completed a year earlier than originally planned.

Sustainability

• Employment of personnel from the region
• Use of recycled construction materials from demolished concrete on the site