Fire protection of suspension bridge cables

Abstract

This paper presents an approach for fire protecting suspension bridge cables against vehicle fires. Over the last 10-20 years, a number of accidents have resulted in severe truck fires on bridges. In Denmark, a severe truck fire occurred in 2013 on the New Little Belt Bridge causing extensive damages. In 2019, a vehicle fire was also reported on the First Bosporus Bridge in Turkey. The awareness of fire risk to transportation infrastructure is now global. Experiences from fires in lorries/trucks carrying normal but flammable goods show that such fires may have a temperature development equivalent to a hydrocarbon fire with temperatures up to 1100-1200 °C. This means that the fire risk of bridges may have been underestimated. In a future with increasing traffic density, it is expected that there will be an increasing need for fire protection of bridges. The fire risk is particularly large for cable borne bridge where cable elements are vital for the structural integrity. The recognition of this concern was the reason for carrying out fire protection of the main cables on the New Little Belt Bridge in 2016-2017 and in 2018-2020 for the Great Belt Bridge. For these bridges the fire risk was assessed through fire simulation of cable cross sections and clam interface with suspenders. Based on the need for fire protection, an innovative concept was developed using a combined numerical and experimental methodology approach for verification. The progress of fire protection realised through the actual fire protection jobs was followed up through an R&D project. The project resulted in an efficient fire protection method, fully verified by large scale fire furnace testing. The installation works on the bridge showed that the concept was very efficient to install with minimum consequences regarding traffic, and also future inspection and maintenance.