Improved time-hardening creep model for investigation on behaviour of pre-tensioned steel strands subject to localised fire

• Published in: Fire safety journal Vol. 116; p. 103191
• Main Authors: Du, Yong, Richard Liew, J.Y., Jiang, Jian, Li, Guo-Qiang
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier Ltd 01.09.2020; Elsevier BV
• Subjects: Cable stayed roof systems; Cable-stayed bridges; cameras; Charge coupled devices; computer software; Creep rate; Damage assessment; finite element analysis; Finite element method; Fire damage; fires; High temperature; High-temperature creep model; Investigations; Localised fire; Material property at elevated temperature; Mathematical models; Mechanical properties; mechanical stress; Parameters; Pre-tensioned steel strand; Prestressing; Regression analysis; Steel; Strain; Strands; Structural damage; Suspension bridges; Temperature; Temperature distribution; Tensile stress; Material property at elevated temperature; Localised fire; Pre-tensioned steel strand; High-temperature creep model
• ISSN: 0379-7112; 1873-7226
• DOI: 10.1016/j.firesaf.2020.103191

Pre-tensioned steel strands as basic elements have been widely used in hybrid string structures, cable suspension roofs and cable-stayed bridges. There is a growing need to evaluate the damage of such structures whenever subjected to fire. The aim of this research is to experimentally and numerically investigate the behaviour of pre-tensioned steel strands considering the effect of creep strains at elevated temperatures. A charge-coupled device camera (CCDC) system is used to capture the high-temperature creep strain of steel strands accurately. A regression analysis is carried out to develop a set of new parameters for Time-Hardening creep model based on the test results of 1860 MPa strands twisted by 7 wires. The test results show that target temperatures influence the high-temperature creep rate more greatly than pre-stressing ratios. The Time-Hardening creep model with new parameters is used in finite element software ANSYS to investigate the mechanical behaviour of pre-tensioned steel strands subject to localised fires. The influencing factors include the pre-tensile force ratio, span length of steel strands, temperature distribution along strand length and fire location. The numerical results indicate that the tensile force in steel strands reduces more greatly as high temperature creep strain is taken into account. Pre-tensioned steel strands will fail when the rupture strain rather than the ultimate tensile stress is achieved at elevated temperatures.