with Professor Dirk Proske of Berner Fachhochschule.
Summary
Bridge collapses are a complex phenomenon influenced by a variety of factors, including material aging, structural errors, natural disasters, and climatic changes. The type of bridge and the materials used play a crucial role in its lifespan and susceptibility to damage. In the future, expertise and international cooperation will be essential to ensure the safety and durability of bridges in a changing environment.
Types of Bridges
- Wooden Bridges: One of the oldest types of bridges, primarily used in antiquity and the Middle Ages. Gaining popularity again.
- Stone Bridges: Known from Roman times, often in the form of arch bridges.
- Steel Bridges: Popular since the 19th century, especially for railway tracks.
- Composite Bridges: A combination of steel girders and concrete slabs. Popular in the early 20th century.
- Reinforced Concrete Bridges: Widespread since the 20th century, especially in the 1960s and 1970s. Larger bridges are usually prestressed. Examples include slab, slab-beam, and box girder designs.
- Suspension and Cable-Stayed Bridges: Used for very large spans.
Causes Of Bridge Collapses
- Floods and Fluvial Processes:
- The most common cause, responsible for about 50% of bridge collapses.
- Effects: Scour, clogging, channel shifting, and debris flows.
- Collisions:
- Ship collisions (e.g., USA, Germany).
- Vehicle collisions (e.g., Eschede, Germany).
- Train collisions.
- Material Fatigue and Aging:
- Especially dangerous for reinforced concrete bridges from the 1960s and 1970s. Fatigue is also a major concern for old steel bridges.
- Construction Errors and Lack of Maintenance:
- Poor construction or inadequate maintenance can significantly shorten the lifespan of a bridge.
- Natural Disasters:
- Earthquakes, storms, avalanches, and rockfalls can cause structural damage.
- Human Errors:
- Planning and construction mistakes, as well as improper use or maintenance. Exceeding the allowed load during special transports/trains.
Frequency and Change Over Time
- Historical Development:
- Bridges from Roman times: Longevity due to massive stone construction.
- 19th century: Increased use of steel, with some collapses due to material fatigue.
- 20th century: Reinforced concrete became dominant, prone to damage from chlorides and poor construction quality.
- Current Trends:
- Average lifespan of reinforced concrete bridges in Europe: 40-70 years.
- Bridges in Asia (especially China): Rapid growth, sometimes shorter lifespan due to fast construction pace.
Future Due to Climate Change
- Temperature and Local Differences:
- Higher temperatures can cause material expansion and contraction, creating stresses in the structure. However, this is not yet observed. High temperatures can also increase water absorption, leading to heavy rainfall.
- Heavy Rainfall:
- Increases the risk of floods and fluvial processes. There are indications that climate change will cause local (e.g., between two neighboring communities) differences in the size and frequency of floods.
- Avalanches:
- Temperature changes could lead to more wet snow avalanches in mountainous regions, potentially causing bridge collapses.
Examples Of Bridge Collapses
The following examples mentioned by Professor Dirk Proske illustrate the variety of causes for bridge collapses, from war-induced overloads and poor maintenance to collision accidents and natural disasters:
- Bridge in Porto, Portugal (Napoleonic Wars):
- Cause: Overload due to a concentration of fleeing soldiers and horses.
- Death Toll: Over 1,000.
- Details: The bridge collapsed as Napoleonic troops entered the city and a large crowd crossed the bridge.
- Train Accident in Eschede, Germany (1998):
- Cause: Collision.
- Death Toll: Over 100.
- Details: An ICE train derailed and hit a bridge, causing a catastrophic collapse.
- Pedestrian Suspension Bridge in India:
- Cause: Overload and poor maintenance.
- Death Toll: About 140.
- Details: The bridge collapsed when too many people were on it, and it was likely inadequately maintained.
- Schraudenbach, Germany:
- Cause: Collapse during construction.
- Details: The bridge collapsed during construction.
- Bochum, Germany:
- Cause: Collapse during maintenance.
- Death Toll: One fatality.
- Details: Collapse during maintenance work on a bridge.
- Ship Collision in Krems, Austria (2005):
- Cause: Ship collision.
- Details: A bridge pier was shifted by two meters, nearly causing a collapse. The train driver was able to stop in time.
- Mudslide in China (1980s):
- Cause: Collision with a mudslide.
- Death Toll: About 200.
- Details: A mudslide destroyed a bridge behind a tunnel. A train passed through the tunnel and crashed as the bridge’s destruction was not noticed in time.
- Passenger Ship Collision with Railway Bridge in Russia (1980s):
- Cause: Collision with a passenger ship.
- Death Toll: Nearly 180.
- Details: A ship collided with a railway bridge, tearing off a cinema hall on the ship, and many passengers died.
Professionals and Knowledge Transfer
- Key Professionals:
- Civil engineers specializing in bridge construction and maintenance.
- Risk managers who oversee and assess the safety of structures.
- Knowledge Transfer: Essential for preventing bridge collapses is the exchange of best practices and research findings. This is particularly challenging because construction practices have changed over time. Bridges are being re-evaluated based on new standards different from those used during their construction. Understanding and considering old construction techniques and standards are crucial for correctly interpreting current preservation norms. Good collaboration between academic institutions, engineers, and government agencies is important.
