Abstract
This paper aims to (1) study ductile fracture behavior, and (2) provide a computational tool for predicting fracture initiation in ASTM A572 Gr. 50 structural steels under axisymmetric tension loading are heated to elevated temperatures and cooled down in air and in water. Employing the post-fire test results reported in the literature for A572 Gr. 50 steels, this paper carries out coupon-level finite element (FE) simulations to capture the stress and strain fields and explore the micro-mechanism of post-fire fracture in ASTM A572 Gr. 50 steels, respectively. Numerical results show that the effects of the experienced temperature and cooling method on fracture parameters are more significant for the steels cooled after being heated to temperatures from 800 °C to 1000 °C than those from 500 °C to 700 °C, due to microstructural changes during the cooling process. Air-cooled and water-cooled specimens show an improvement and a significant reduction in ductility, respectively. A modified void growth model (VGM) is proposed by introducing two additional temperature-dependent functions, through which the effects of elevated temperature and cooling method on fracture behavior are quantitatively analyzed. Limitations of this study are also discussed.
Highlights
Structural fire accidents commonly result in the loss of life and property [1,2]
SEM fractographs show that the fractured surfaces consist of the micro-void coalescence (MVC) zone and the river-like surface, relevant to ductile fracture initiation and brittle fracture propagation, respectively
It leads to changes in the microstructures of the steel samples, the additional heating and cooling process is not likely to influence the micro-mechanisms of ductile fracture initiation and the ultimate failure mode
Summary
Structural fire accidents commonly result in the loss of life and property [1,2]. Steel structures experience excessive deformations and deterioration in mechanical behavior during and after a fire accident, partly due to the significant degradation of mechanical properties of structural steels after exposure to high temperatures [5]. Previous fire accidents have shown that numerous steel structures, though undergoing severe local damage, avoided complete collapse due to sufficient structural redundancy, as well as assistance from passive and active fire protection systems [6]. A reliable and accurate assessment of post-fire mechanical performance at the structural level is strongly dependent on the understanding of post-fire mechanical properties of steels at the material level, which provides fundamentals for the evaluation procedure for the post-fire reusability of steel structures
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
