Experimental investigation on combustion characteristics of steel cable for cable-stayed bridge

Inspired by a serious fire accident on the cable-stayed bridge, the characteristics of this type of cable fire were investigated pertinently with experiment. And some important parameters, such as temperature distribution and flame height, were measured. The behaviors of fire growth and fire propagation were analyzed; furthermore, fire spread rate was obtained. Additionally, the effectiveness of fire extinguishing methods used in such cable fires was also examined. The results show that the special cables layout and material composition seriously influenced fire behaviors. When internal steel strands were ignited, the polyethylene material on its surface would melt and drop at high temperature, causing that external burning drops penetrated into the interior, which could gradually ignite the unburned part and flaring up the fire. The HDPE sheath originally as a protected component, once ignited, would generate a large amount of burning molten drops, dramatically promoting the fire development to the underneath cable. As observed in fire extinguishing experiments, dry powder, one method recommended by NFPA, showed a re-ignition phenomenon. By comparison, water, one method deprecated in standard, contrarily brought about good effects in fire extinguishing due to an effective cooling effects for inner steel.