Comparative investigation on fire resistance of different fire prevention schemes for 1670 MPa steel wires used in bridge cables

Abstract

This paper mainly investigated the fire resistance of different fire prevention schemes for 1670 MPa steel wires used in bridge cables. The fire resistance tests on bridge cables under different fire protection schemes were carried out. The failure modes and the varied patterns of temperature at different positions of the cables was studied, and the optimal design scheme of fire protection for bridge cables was also obtained. Furthermore, the tensile test of steel wire after fire was carried out to study the degradation law of mechanical properties of steel wire. The results showed that the cables undergo varying degrees of bending deformation after the fire, mainly due to the poor fire protection effect. The wrapping process of the fire protection scheme was a key factor affecting the protective effect. When the premature invalidation of the wrapping mode failed to occur, the aerogel material would have better thermal insulation behavior than the basalt fiber. The temperature rising rate of Schemes D (6 mm ceramic fiber aerogel tape), E (10 mm high silica glass aerogel tape) and F (10 mm nano thermal isolation felt-ceramic fiber aerogel) was relatively gentle, and the temperature of most measuring points within 4500s was not more than 300 °C. Based on the failure mode and the temperature of the cables, it could be judged that Schemes E and F were better than Schemes C (4 mm composite fiber fire-resistant isolation tape) and D while schemes A (4 mm basalt fiber needled felt) and B (4 mm aerogel tape) had the worst fire protection effect. Due to the surface temperature, the fracture morphology of steel wires after fire varied greatly, mainly divided into brittle fracture and ductile fracture. With the increase of temperature, the yield and ultimate strength of steel wire of Schemes A, B, C, D and E decreased greatly after fire, and along with a maximum decrease of 73.78% and 69.02% respectively.