High-temperature mechanical properties and failure modes of UHSS wire for cable-supported bridge

The frequency of fire accidents in cable-supported bridges is increasing, but the ultra-high strength steel (UHSS) wire for cable-supported bridges lacks a unified expression of the degradation law of its high-temperature mechanical properties. Therefore, for the emerging 1960 and 2060 MPa UHSS wires, a series of steady-state tests are carried out in this study. The stress-strain response, elastic modulus, yield strength, ultimate strength, ultimate strain, and failure strain of the UHSS wires in the temperature range of 20-900 degrees C are obtained, as well as the failure parameters such as elongation and shrinkage after rupture. Based on the test data, a calculation model suitable for the prediction of the degradation law of high-temperature mechanical indicators of 1670--2060 MPa UHSS wire is established. Experimental investigations show that the stress-strain development process of UHSS wire at elevated temperature can be described by a three-stage model. Due to differences in chemical composition and manufacturing process, there are significant differences in the degradation patterns of mechanical indicators of different steel materials at elevated temperatures. The failure mode of the steel wire is brittle failure when the temperature does not exceed 200 degrees C, but the failure mode changes from brittle failure to plastic failure when the temperature exceeds 200 degrees C. Compared with the existing experimental results, it is obvious that the high-temperature mechanical indicator degradation model of high-strength steel wires proposed in this study can be used as input data for computer models to evaluate the fire resistance of cable members of cable-supported bridges.