An from Professor Steffen Marx from the Technical University of Dresden鈥檚 Institute of Structural Concrete, who was commissioned by authorities in Dresden to carry out an investigation, found that the cause of the accident on 11 September this year was 鈥渉ydrogen-induced stress corrosion cracking鈥�.

The bridge, which was completed in 1971, suffered corrosion damage during its construction through a combination of manufacturing methods employed 50 years ago and the influence of the weather on the steel while it was being built, the investigation found.

That corrosion, combined with material fatigue caused by traffic stress, led to the bridge鈥檚 failure. Over 68% of the tendons in the carriageway on the collapsed section were found to be severely damaged to the point of failure.

Nonetheless, the probe also found that city authorities had inspected the bridge in accordance with applicable standards and recommendations and had commissioned special reports. It concluded that there was no negligence on behalf of those responsible for the bridge.

Remaining sections will have to be demolished

The Communist-era Carola Bridge, which crosses the River Elbe, partially collapsed in September. It is a 32m-wide, pre-stressed concrete box girder bridge, built between 1967 and 1971 by VEB Br眉ckenbau Dresden.

It consists of three superstructures with two piers, one of which sits in the river. The span at the northern end of the bridge is 58m long and the bridge was reputed to be the pre-stressed concrete bridge with the largest span in East Germany (GDR).

Centro鈥檚 excavator operators worked through the night to tear down the structure. (PHOTO: City of Dresden)

The bridge carries four lanes of road traffic and two tram tracks. The two sections of the bridge carrying road traffic (sections A and B) had already undergone maintenance in phases running between 2019 and 2024, according to reports. The section of the bridge affected carries the tram lines (section C) and had been scheduled for maintenance work next year. Around 100m of that section of the bridge collapsed.

But Prof Steffen and his colleagues have concluded that the damage to the bridge is so severe that bridge sections A and B cannot be put back into operation. The City of Dresden said that a replacement is now 鈥渦rgently needed鈥�.

The City of Dresden said it wanted to allow shipping to start passing under the bridge as soon as possible. That means it is continuing with the demolition of the partially collapsed section C of the bridge. It will expand an acoustic monitoring system on sections A and B.

The monitoring system records in real time whether there any further breaks in the pre-stressed steel tendons within the bridge. It should deliver the first data by mid-January 2025 and if the bridge sections are determined to be sufficiently stable, river traffic will be restored.