# Ultimate Compressive Strength of H-Section Stub Columns Subject to Random Fitting Corrosion Damage
## 5 Conclusions  
Compressive behavior and ultimate strength of randomly pitted H-section stub columns were numerically investigated under various corrosion patterns and different levels of pitting intensities, using a proposed method for modeling random pitting corrosion. This study verified different approaches to address the thickness loss resulting from random pitting corrosion, according to current design standards. Additionally, stochastic simulations were used to elucidate the degradation law of compressive strength, and the mechanism of structural failure in randomly pitted H-section columns. The following conclusions can be drawn.  
1. The proposed modeling method can replicate the impact of random pitting corrosion on compressive strength and failure behavior of damaged H-section stub columns. It leads to availability to reflect the variation in compressive strength caused by the random nature of pitting corrosion that is not captured by the method based on simplified regular corrosion pits or uniform corrosion.
2. Corrosion damage on the column flange causes more reduction in ultimate strength and axial stiffness than that on the column web. For the columns with corrosion damage simultaneously on web and flange plates, the reductions in strength and stiffness can be linearly superposed by the reductions in the strength and stiffness of individual plates. For the columns studied herein at the \(DOV\) 13.8%, the reduction in strength was up to 24.2%, and the reduction in stiffness was about 19.9%.
3. The ratios of width-to-thickness for both flange and web plates have a negligible effect on the strength reduction in a damaged column since the change in such ratios only  
Figure 21: Failure modes of H-section columns (H7.5 \(\times\) 7.5) (displacement contour unit: mm): (**a**) intact model; (**b**) equivalent thickness model; and (**c**) random corrosion model.  
causes less than a 3% strength variation, which is smaller than that caused by random nature of pitting corrosion. However, the column with a larger width-to-thickness ratio may locally buckle due to random pitting corrosion, thereby altering failure mode, with a significant strength reduction.
4. The equivalent thickness method that induces \(-1.25\) times standard deviation of pit depth to account for uneven material loss caused by random corrosion pits, plus the uniform thickness loss, yields a relatively accurate prediction, based on the Chinese and European Standards. For different sizes of flange and web plates under pitting corrosion damage at the \(DOV\) less than 9%, the maximum relative error of predicted results was no more than 5%.  
It is noteworthy that both Chinese and European standards are applicable only within a certain level of pitting intensity and closely related to the web and flange thickness of columns. The empirical formula proposed for plated structures applies to compressive strength prediction of randomly pitted columns, which can consider the uncertainty of strength reduction caused by random nature of pitting corrosion. In addition, based on the proposed modelling method, the statistical features of residual strength of randomly pitted columns can be clarified in further research.  
Conceptualization, R.W.; methodology, R.W.; software, F.W.; validation, F.W. and R.W.; investigation, F.W. and R.W.; data curation, F.W. and J.J.; writing--original draft preparation, F.W. and J.J.; writing--review and editing, R.W.; supervision, R.W.; project administration, R.W.; funding acquisition, F.W. and R.W. All authors have read and agreed to the published version of the manuscript.  
This research was funded by [Postgraduate Research & Practice Innovation Program of Jiangsu Province] grant number [SJCX23_2223].  
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The authors declare no conflict of interest.