Seffersbachbrücke – Seffersbach Bridge

Last surviving “Möller system” suspension boom bridge in Saarland

Merzig is home to a historic structure that for many years was largely ignored: the Seffersbach Bridge that forms part of Trierer Straße. For a long time, industrial and pure civil engineering structures were very much seen as the poor relations of traditional historic monuments such as castles, churches and the like. This was unfair, as they too bear witness to the architectural practices of their era. In fact, bridges often provide a more impressive demonstration than other structures of the innovativeness and engineering capabilities of their builders. The Merzig bridge only attracted the recognition it deserves when it underwent general renovations, after which it was added to the national register of listed buildings as part of the “German Heritage Day” held on 12th September 2004.

The bridge was constructed by the Braunschweig-based company Drenckhahn & Ludkop in 1901. The Neo-Baroque décor of the side pieces of the cement side panels was very much in line with the contemporary taste for historic styles: a stylised egg and dart motif on each outer suspension boom with volutes on the abutments. In 1936, the west side of the bridge was widened to incorporate a footpath. This meant that the decorative features were no longer visible. During the renovation work, the bridge was restored to it original condition. This construction method was developed by Max Möller (1854-1935). He worked as a government building officer in Hamburg, Karlsruhe and Leipzig. From 1890, he was a professor at Braunschweig Technical University. In conjunction with the construction company mentioned above, he developed this bridge construction method and patented it in 1894.

Back then, there were very few established calculation methods for demonstrating structural strength. The load bearing capacity was determined using test loads. The exceptional feature of this bridge is the design. When a load is applied to a support, no matter the span, compression forces occur on the upper side and tensile forces on the lower side. Concrete can absorb compression forces with no problem, but reaches its load limit very quickly when subjected to tensile forces. By contrast, iron or steel is also capable of transmitting tensile forces. As a result, the engineers more than a hundred years ago came up with the idea of developing composite structures. The first experiments of this type included the suspension boom bridges developed by Prof. Möller at the end of the 19th century. They are based on a T-beam construction made up of concrete supports combined with fish-belly shaped flat iron ties on the underside. A series of adjoining beams of this type in trussed cast concrete were combined to form a plate made up of slabs.
The lower flat iron bars were anchored in the concrete with steel brackets. No actual reinforcement (iron inside the concrete) was used. The flat iron was merely plastered over.

Between 1894 and 1920, more than 500 Möller bridges were constructed in Central Europe. Just a few examples remain today. The “Möller system” ultimately failed to establish itself. Today, all bridges are reinforced ferroconcrete structures. However, the development of civil engineering has depended on these kinds of innovations, even those that ultimately proved to be blind alleys. The bridge here impressively documents the first methods using reinforced concrete as a building material, without which our modern built environment would be unthinkable.

This bridge over the Seffersbach is the last preserved example of this type of structure in Saarland, making it one of the most notable transport structures in the region.

The Saarland state conservator’s office (Staatliche Konservatoramt des Saarlandes) has created a bilingual brochure in German and French, which is available to download in PDF format.