# Ultimate Compressive Strength of H-Section Stub Columns Subject to Random Fitting Corrosion Damage
## 1 Introduction  
H-section columns are widely used in various industries and applications due to their high load-bearing capacity and stability [1]. However, when exposed to corrosive environments, such as marine or industrial environments, steel material can deteriorate over time. The random corrosion of H-section columns poses significant risks to the structural stability and safety since it can reduce load-bearing capacity and compromise structural integrity [2]. It is, therefore, important to understand the behavior of the columns under different corrosion conditions, and develop accurate models to predict their load-carrying capacity for maintaining safety and sustainability and preventing catastrophic failures. In harsh servicing environments, especially the marine environment, steel structures often suffer from failure of the coating and cathodic protection, resulting in different types and levels of corrosion damage [3]. Ultimate strength is the primary consideration for determining their actual safety margin [4, 5]. In this context, two typical columns with tubular and H-sections have been widely considered. The compressive strength of circular steel tubes with general (uniform) corrosion damage aroused more attention, and numerous experimental and numerical studies were conducted to explore the effects of location and degree of corrosion damage on strength reduction [6, 7]. It was reported that the failure mode of corroded steel pipes was not affected by general corrosion, which leads to uniform thickness loss over the entire member, but by localized uniform corrosion, which causes local thickness loss in part of surface of the member. In particular, its location has asignificant impact on residual bearing capacity, with an unfavorable effect in the middle of the tube more than in the end. In the case of the combination of internal pressure and bending, corrosion damage, in spite of causing a localized uniform thickness loss, had a significant impact on the ultimate bearing capacity of thin-walled steel pipes [8]. This was due to the fact that the bending capacity of corroded pipes drastically decreased with the increase in corrosion depth. On the other hand, corrosion along the circumferential direction of the pipe had a more adverse effect on the bending behavior of corroded pipes compared to that along the longitudinal direction. Compared to general corrosion, random pitting corrosion, which is widely spread or locally distributed on the member, can lead to a more serious reduction in ultimate strength under the same degree of corrosion damage [9; 10]. Particularly, the random nature of pitting corrosion in the size, shape and distribution of corrosion pits results in a significant variation in ultimate strength. The ultimate strength of H-section steel stub columns with artificial corrosion, mechanically introduced with localized uniform corrosion, was experimentally studied under uniaxial compression [11]. It was shown that the localized reduction in flanges in an asymmetric pattern had an insignificant impact on the axial strength of columns, and the degradation of flange thickness more significantly reduced the axial strength of tested columns than the web degradation. More compression tests were performed on H-shaped steel columns with corrosion damage, induced as general corrosion by accelerated corrosion tests, to study the failure mode, local buckling load and ultimate load [12]. The failure mode of columns may be affected by the corrosion, with gradually decreased half-wavelength with the increase in corrosion intensity, transforming from strength failure to instability. Meanwhile, the ultimate compressive load of the columns was only dependent on the damage degree of the weakest section with corrosion damage. However, the general corrosion had no influence on the failure mode of four-point bending H-section beams, regardless of whether it caused degradation in the bearing capacity, stiffness and ductility [13].