Size effect on CFST-column seismic performances at cryogenic temperature via mesoscale simulations

Abstract

The macro-mechanical performances of CFST column at low temperatures can be significantly affected by three main factors: the change of meso-material properties, the filling and frost heave effects caused by pore ice, and the interaction between each meso-component. Therefore, a three-dimensional thermo-mechanical sequential coupling mesoscopic simulation method was established and verified by existing experimental results with the maximum errors within 10 %. The seismic performances of CFST columns with various cross-section sizes (200–800 mm) at different temperatures (20, −30, −60 and − 90 °C) were simulated and investigated, with focused on the damage mechanism and quantitative analysis of the low-temperature effect on various seismic performance indexes (i.e., hysteretic characteristic, nominal shear strength, ductility, energy dissipation and reparability) as well as the corresponding size effects. The results indicate that the low temperature can increase the nominal strengths (i.e., peak strength, yield strength and ultimate strength), but weaken ductility, energy dissipation capacity and reparability of CFST columns. With the increase of cross-section size, the reparability increases, while other seismic performance indexes decrease, showing the size effect, which tends to be more obvious at low temperatures. The size effect on peak strength at −90 °C is enhanced by 115.5 % than that at 20 °C, while 127.9 % for yield strength and 113.5 % for ultimate strength. Based on research results, a modified size effect formula for calculating shear strengths of CFST columns considering the influence of low temperature and structural size was developed, which can provide references for seismic design of large-sized CFST columns in extreme low temperature environments.