Seismic performance of reinforced concrete beams under freeze-thaw cycles

Previous studies have shown that freeze-thaw cycle (FTC) action in severe cold environments is a durability issue that seriously threatens the seismic performance of concrete members. However, research on the seismic resistance of reinforced concrete (RC) beams under FTC action is still scarce. This paper presents an experimental study of six undamaged and frost-damaged RC beams subjected to a low-cycle reciprocating load. The paper aims to investigate the influences of FTC number and concrete strength on the seismic resistance of damaged beams. The paper reports on frost damage at different levels, cyclic damage process, hysteresis response, strength, ductility, shear deformation, and energy dissipation. The test results demonstrate that as the FTCs rose, the width and number of frost-heave cracks on the surface of the beam gradually increased. Moreover, frost action had a significant negative effect on strength, deformation, and energy dissipation, especially when the beams were highly frost-damaged. Further, the shear deformation and shear component to whole deformation gradually increased. Based on the experimental results, a time-dependent evaluation model is proposed to estimate the residual capacity of key elements of RC frame structures in severe cold climates, taking into account the effects of FTCs, concrete strength, and uneven distribution of freeze-thaw damage.