Study on pull-out behavior of headed studs embedded in concrete slabs at low temperatures

To promote the application of composite structures in polar and cold regions and solve the problem of lack of research on pull-out behavior of headed studs at low temperatures, four groups of pull-out tests on headed studs embedded in concrete slabs were conducted by a self-balancing loading device. The parameters in the test were low temperature levels (20 ℃, -30 ℃ and -60 ℃) and effective embedment depth of headed studs (57 mm and 92 mm). The failure modes, load-displacement curves and tensile resistance were discussed. Considering the difficulty and cost of experiments for large specimen in low-temperature environment, finite element (FE) models were developed based on the test results to simulate the pull-out behavior of specimens. The proposed FE models could capture identical simulations on pull-out behavior of headed studs at different low temperatures varying from 20 ℃ to -60 ℃, in terms of load-displacement curves, ultimate tensile resistance and failure modes. Then parametric studies were carried out with the validated FE models to study the effects of low temperatures (20 ℃, -30 ℃ and -60 ℃) and effective embedment depth (48 mm,64 mm,80 mm and 92 mm) of studs on the pull-out behavior of headed studs. The results show that three typical failure modes are observed in the temperature range of 20 ℃ to -60 ℃, i.e., concrete breakout failure, splitting failure and steel failure. The tensile resistance, ultimate displacement and initial secant stiffness of specimens increase with the decrease of temperature and the increase of effective embedment depth, and the increase of the effective embedment depth has a more significant effect on the improvement of the pull-out behavior of headed studs. When the temperature is not higher than -30 ℃, the failure mode of specimens with effective embedment depth of 92 mm of studs occurs steel fracture, in which case the pull-out behavior of specimens mainly depends on the mechanical properties of headed studs. Through the numerical simulation and parameter analysis, it can be concluded that the critical value of the effective embedment depth of stud to its diameter is within the range of 5 to 6 when the failure mode of pull-out specimen with concrete grade of C60 changes from concrete breakout failure to steel fracture at the temperature of 20 ℃ to -60 ℃. © 2021, Editorial Office of Journal of Building Structures. All right reserved.