How the ideas of Dresden-based structural engineers offered an architectural monument a new lease on life

André Terpe

In 1893, Naumburg’s Thainburg Bridge was built – a trailblazing construction innovation. Built by the Joint-Stock Company for Monier Construction (Actiengesellschaft für Monierbauten), it was the first bridge in German to use Eisenbeton, or “iron concrete” – an early German name for reinforced concrete. For many years, it was also known as Monier concrete and the reinforcement bars inside as Monier iron after the Frenchman Joseph Monier, who is considered to be the inventor of this technology. Monier’s construction technique caught on quickly. His ideas had a great impact on the construction industry, particularly in Germany, and were quickly introduced in practice and refined.

Today, nearly 130 years later, the bridge is in need of restoration. In 2017, it had already been tendered for demolition and replacement. However, anyone who has seen Thainburg Bridge can understand why the Naumburg City Council recognized its importance as an architectural monument. After comprehensive consideration as to an appropriate and expedient renovation of the bridge, it became clear that only carbon concrete would fit the bill, since the proportions of the construction elements would be distorted by a reinforced concrete support. The renovation will involve a 12 mm thick layer of carbon concrete, which will include 12 load-bearing reinforcement layers of carbon mesh (carbon reinforcement). The representatives of the city’s cultural heritage management and city officials were convinced that it was justified to renovate what was in its time an extremely innovative bridge using a contemporary technical innovation. Will Naumburg’s bridge go down in construction history for a second time?

For about a year now, Dr. Harald Michler from TU Dresden’s Institute of Concrete Structures has devoted his work to the particularities of Thainburg Bridge. His involvement is crucial because at the moment, the use of carbon concrete only has general building approval certification for use in interior spaces. “In interior spaces, the carbon concrete elements are not subjected to temperatures of above 40 degrees or continuous dampness,” explains Dr. Michler. Following in-depth investigations of the circumstances at the site, he is convinced that the conditions for exterior use can be established in this special case in compliance with the regulations in place. That means that Thainburg Bridge meets the approval requirements. Thanks to this pioneering technology, the bridge could continue to stretch across the Naumburg city moat for up to another 100 years.