A passive fire protection method for main cables and slings of suspension bridges utilizing fiber felt/aerogel composites

The paper proposes a fire protection method for the main cables and slings (cables for short) of suspension bridges based on fiber felt/aerogel composites. Glass fiber felt/aerogel composite (GFAC), basalt fiber felt/aerogel composite (BFAC), and high silica fiber felt/aerogel composite (HSFAC) were prepared using silica aerogel as filler. Heat-shielding tests and thermal stability analysis were conducted on these three thermal insulation composites. A fire test platform was established to study temperature distribution and fire protection range of suspension bridge cables. The following results were obtained: (1) Within 6000 s, the 5 mm-thick HSFAC can resist 700 °C butane fire, while 7 mm-thick HSFAC blocks 1000 °C flame. The 10 mm-thick HSFAC provides better thermal insulation. (2) Two fire protection zones are identified according to temperature ranges of 1000 °C to 700 °C and 700 °C to 300 °C, respectively, with minimum heights of 12.8 m and 20.8 m. (3) For a 90-minute fire protection, the main cables in the former zone are wrapped with 10 mm-thick HSFAC, while the slings are chosen to be 7 mm-thick HSFAC. In the latter zone, main cables and slings are covered with 5 mm-thick HSFAC. The fire protection method has been implemented on a suspension bridge in Guangzhou, China.