In-situ measurements of temperature and strain fields of large-diameter concrete-filled steel tube columns and the refined finite element modeling

Abstract

Concrete-filled steel tube (CFST) columns are prevalent in transmission towers and arch bridges due to their cost-effectiveness and superior mechanical performance. The growing megastructures lead to large-diameter CFST components, which are exposed to the risk of early-age thermal concrete cracking. In this study, temperature and strain fields of two 2.1 m-dia. CFST columns were monitored in-situ. Within 30 h, the peak temperature and tensile strain at the centroid reached 97.0°C and 400 με, respectively. Meanwhile, temperature fields of eight scaled CFST columns were also monitored and compared. In addition, ultrasonic pulse velocity test was performed to detect the early-age thermal cracking. To predict the temperature and strain evolutions accurately, a refined numerical model is proposed, considering coupled mechanical, hydration and thermal processes. It is revealed that the model could accurately predict the temperature and strain evolutions of CFST columns. Furthermore, experiments and numerical simulations illustrate that thermal cracking would likely be triggered in CFST components with diameter greater than 1.2 m.