Mechanical properties of 2100 MPa parallel wire strands under and after elevated temperature

Abstract

In this study, steady-state tensile tests were conducted at elevated temperatures and after cooling from elevated temperatures on 2100 MPa galvanized parallel wire strands (19 × 5.4 mm) used in long-span suspension bridges. Data collection was done using a charge-coupled device camera (CCDC) system. The results from tests at elevated temperatures indicate that the mechanical properties of parallel wire strands deteriorated gradually with increasing temperature. This degradation trend was well described by logistic curves. The results show that the mechanical properties after elevated temperature decreased significantly when the temperature exceeded 350 °C. By comparing with existing research, it was found that the higher the strength grade, the more severe the strength degradation after elevated temperature. During heating and cooling stages, moderate tension led to beneficial effects on residual strength of the specimens. This applies to temperatures below 400 °C. A linear-exponential-linear (L-E-L) stress-strain model was proposed to establish stress-strain equations for parallel wire strands at and after elevated temperatures. Degradation equations were also obtained for elastic modulus, yield strength, ultimate strength and proportional limit. These findings can be utilized to analyze fire resistance performance of cable systems in large-span bridges and assess post-fire damage.