The effect of inclination angle on fire behaviors of stay cable in an intercepted double-layer cable model

Abstract

Understanding the fire characteristics of stayed-cable bridge, such as fire growth, during accidental fire is essential to develop prevention strategies for potential damage. This study focuses on the effects of high cable fire that may result from a short circuit or a lightning strike since high flammability heat release characteristics of HDPE sheath causes burning of nearby cables. Fire propagation behaviors on one single cable and between two adjacent cables under working conditions with different inclination angles were obtained. The temperature distribution, drop ignition behaviors and flame spread rate were analyzed. The results show that flame propagation characteristics of stay cables seriously changed as the angle of inclination increases, which explain the fracture sequence of cables to some extent for the Red Stone Bridge fire event. The particle size of molten substance formed by combustion of the upper-layer cables increases, and the ignition position for the under-layer cable gradually moves down as the increase of inclination angle. Moreover, increased inclination angle also resulted in increase in flame height and molten drops flow rate and reduce in the duration of the prosperity stage for cable fire. Although HDPE sheath is a protective device, it does prevent the combustion for inner strands from becoming intense, but once ignited, would become the main fire load, promoting fire development.