Elevated-temperature mechanical property and constitutive model of Galfan-coated and full-locked steel cables

Abstract

Steel cables are an essential stress-bearing member in pre-tensioned steel structures. Their exposure to fire may lead to prestress loss, which may cause structural failure or even overall collapse. This study used a non-contact strain measurement system to investigate the mechanical properties of 1670 MPa Galfan-coated steel cable and 1570 MPa full-locked steel cable at elevated temperatures. The test results showed that the mechanical properties of the two types of cable decayed significantly with the increase in temperature. At 700 °C, the ultimate strength of Galfan-coated steel cable was only 2.36% of that at room temperature, and that of full-locked steel cable was 3.56%. By analyzing the stress-strain relationships between the yielding and hardening stages at 9 test temperature levels, it was found that the high-temperature nominal yield strength could be taken as the stress at the strain level of 1.25% for both types of steel cables. Based on the full stress-strain curves at each temperature level, the calculation formulae for high-temperature reduction factors of elastic modulus, proportional limit, nominal yield strength, and ultimate strength of Galfan-coated and full-locked steel cables were proposed. Besides, the high-temperature constitutive models of the two cable types were also proposed based on the experimental data. The findings of this study can improve the fire safety of pre-tensioned steel structures.