Replacement of the Reuss Road Bridge
Author: Elias Müller
Language: German
Abstract
The existing Reuss Bridge in Ottenbach, a three-span prestressed slab bridge built in 1955, no longer meets current standards for traffic loads (SIA 261:2020). Within the scope of this master’s thesis, a preliminary design for a replacement structure was developed, with particular consideration given to the reuse of the existing substructure.
The new structure, replacing the existing Reuss road bridge, is designed as a three-span prestressed slab girder bridge. The superstructure is monolithically connected to the modified existing piers and supported on bearings at the abutments. The girder depth and web width vary along the bridge axis, increasing near the piers to enhance load-bearing capacity and ductility. The continuous structural system with floating bearings, combined with the omission of expansion joints at the abutments, significantly reduces maintenance requirements (semi-integral bridge).
The bridge geometry was modelled in Grasshopper (Rhino) and transferred via defined interfaces to SOFiSTiK for structural analysis. The structural model consisted of a grillage system with two symmetrical slab girders and transversal beams to represent load distribution. The modelling approach, though simplified due to time and software constraints, is suitable for the preliminary design phase and fulfils the necessary verifications for structural safety and serviceability.
The deconstruction of the existing bridge would be carried out in sections using a temporary auxiliary structure, with pier heads removed by hydrodemolition while preserving the reinforcement for the monolithic connection with the superstructure. The new superstructure is designed to be constructed in three stages, with the auxiliary structure being reused and repositioned for each stage.
The estimated construction costs amount to approximately CHF 4.1 million (±30%), based on simplified quantity take-offs, preliminary design drawings, and reference prices from a similar project from 2018.
Overall, the study demonstrates a technically feasible, economical, and aesthetically well-integrated replacement concept. The slender and visually unobtrusive design harmonises well with the surrounding landscape and provides a robust basis for further project development. The concept thus offers a reference for the planned replacement of the Reuss Bridge in Ottenbach on behalf of the Canton of Zurich.
