Constitutive model and mechanical properties of grade 1960 steel wires under fire and post-fire conditions

The structural performance of the bridges under fire accidents has gradually become one of the hot issues in bridge safety. The fire resistance of the cables is a critical factor in the structural performance of cable-stayed bridges. The mechanical properties of 1960 high-strength steel wires at elevated temperatures were investigated in this paper. Tensile tests on steel wires were performed at various high temperatures and after cooling. The failure modes and mechanical properties of steel wires after heating and cooling were investigated in detail. The results show that mechanical properties such as yield strength and ultimate strength are continuously degraded as temperature rises at both high-temperature and after-cooling test, while elastic modulus and elongation are not changed significantly after heating–cooling process. A constitutive model was proposed based on two-segment Ramberg–Osgood model for both high temperature and cooling processes. It is shown that the proposed model well reflects the material behavior for both processes.