# Seismic Performance of Reinforced Concrete Short Columns Subjected to Freeze-Thaw Cycles
## 1 Introduction  
Over the past few decades, concrete structures in cold regions have experienced severe deterioration due to freeze-thaw penetration. For example, certain concrete structures in North China have been affected by this physical procedure, including buildings, bridge piers, and off-shore platforms [1; 2]. The main mechanism of freeze-thaw damage which is widely accepted is related to the 9% volume expansion of freezing water that exists in the concrete pore system, resulting in an increase of hydraulic pressure [3; 4; 5]. As the pressure accumulates and exceeds the concrete tensile stress, cracks initiate and lead to the degradation of concrete properties. A series of experiments [6; 7; 8; 9; 10] were conducted to investigate these degradations on the material level and concluded that in many aspects the apparent deteriorations were produced due to the freeze-thaw action, which comprised concrete compressive and tensile strength, modulus of elasticity, and the bond strength between concrete and reinforcement. In addition to tests on concrete mechanical properties, modern techniques have been used to expose the evolution of frost damage in concrete, including but not limited to X-ray computed tomography [11], ultrasonic imaging [12; 13], and flatbed scanner [14]. Hence, when considering the potential consequences of earthquakes in the seismic area, it is important to quantify the seismic performance of structures subjected to freeze-thaw cycles (FTCs). In comparison to the reality that deep insights into material properties of freeze-thaw damaged concrete have been put forward, the experimental studies on the components level are still limited. Using monotonic loading, [PERSON] et al. [15] tested reinforced concrete (RC) beams using the depth and location of frost damage as variables. Their test results showed that the reduction in the stiffness and bearing capacities was significant. [PERSON] et al. [16] conducted cyclic loading tests on RC squat shear walls with 0 to 300 FTCs. It was concluded that increasing frost damage altered the failure modes ofthe specimens and severely decreased their seismic performance. Recently, [PERSON] et al. [17] studied the seismic behavior of RC beam-column joints with different freeze-thaw damage based on a simulated seismic loading test. As the main load carrying and lateral force resistant member, RC column's hysteretic response is highly vital to the seismic behaviors of RC structures. Therefore, the evaluation of the seismic behaviors of RC columns with freeze-thaw damage should be investigated. In an experimental program carried out by [PERSON] et al. [18], RC columns with varying FTCs were subjected to cyclic loading tests under different axial load ratios. The columns were designed with much larger shear capacity than the flexural capacity due to the large shear span-to-depth ratio (equal to five), and they all showed typical flexure failures despite the difference in freeze-thaw damage. The identical failure modes were also reported in other experimental studies on freeze-thaw damaged columns with the same shear span ratio of five [19; 20]. However, the shear capacity of the RC column was weakened, as well as its flexural capacity, owing to the strength decay in freeze-thaw damaged concrete. In addition, a large portion of the RC short columns are quietly vulnerable during an earthquake attack as observed in post-earthquake investigations [21], where their failure would cause the buildings to collapse. It is known that the shear failure of RC columns or beams is brittle in nature, and therefore it has been examined in a number of studies [22; 23; 24], however, the effect of FTCs on their seismic performance has not been studied yet. Therefore, this study explores the cyclic performance of the aforementioned RC columns damaged by FTCs.