# Ultimate Compressive Strength of H-Section Stub Columns Subject to Random Fitting Corrosion Damage
## 3 Results and Analyses
### Compressive Behavior of Randomly Pitted Columns
#### 3.1.1 Ultimate Strength  
Figure 7 depicts the relationship between the residual strength of H-section columns, subjected to axial compression, and the \(DOV\) under different corrosion patterns. Specifically, Figure 7a showcases the ultimate strength of columns affected by either flange corrosion and web corrosion, aiming to differentiate the location impact of corrosion damage. Figure 7b pertains to the ultimate strength of columns subjected to combined corrosion. In Figure 7a, it is evident that corrosion at the same level of pitting intensity caused a greater reduction in strength for columns with flange corrosion than that with web corrosion. At the lower \(DOV\) of 4.8%, the column with single-flange corrosion (H11.5 \(\times\) 7.5\(-\)SF) experienced a strength reduction of 5.1%, while the column with web corrosion (H11.5 \(\times\) 7.5\(-\)W) demonstrated a strength reduction of 3.9%. However, at the higher \(DOV\) of 13.8%, these strength reductions increased to 9.1% and 6.5%, respectively. Moreover, in the case of double-flange corrosion, the variance in corrosion pit distribution between symmetric and asymmetric patterns had an insignificant impact on strength reduction. Even at the higher \(DOV\) of 13.8%, the strength reductions caused by the symmetric (H11.5 \(\times\) 7.5\(-\)DF) and asymmetric (H11.5 \(\times\) 7.5\(-\)AF) double-flange corrosion were merely 17.8% and 17.4%, respectively, as indicated in Figure 7a. Similarly, a marginal distinction was observed in the combined corrosion scenario at the higher \(DOV\) of 13.8%. The symmetric (H11.5 \(\times\) 7.5\(-\)DF + W) and the asymmetric (H11.5 \(\times\) 7.5\(-\)AF + W) corrosion patterns resulted in strength reductions of 24.2% and 23.5%, respectively, as displayed in Figure 7b. Interestingly, the reduction in ultimate strength of H-section columns resulting from random pitting can be predicted by linearly superimposing reduction in ultimate strength caused by corrosion in each plate element. At a \(DOV\) of 4.8%, the single-flange corrosion column (H11.5 \(\times\) 7.5\(-\)SF) exhibited an ultimate strength of 1895 kN, with a strength reduction of 5.1%, while the double-flange corrosion column (H11.5 \(\times\) 7.5\(-\)DF) displayed an ultimate strength of 1803 kN, with a strength reduction of 9.6%, approximately twice the former, as depicted in Figure 7a. Meanwhile, the ultimate strength observed in the column with web corrosion (H11.5 \(\times\) 7.5\(-\)W) demonstrated a reduction of 3.9%. However, in the case of  
Figure 7: Residual ultimate strength under different corrosion patterns: (**a**) flange and web corrosion; (**b**) combined corrosion. single-flange combined corrosion (H11.5 \(\times\) 7.5\(-\)SF + W), the strength reduction amounted to 8.5%, as shown in Figure 7b, approximately equivalent to the combined reductions from flange corrosion (5.1%) and web corrosion (3.9%). Similarly, the strength reduction for double-flange combined corrosion (H11.5 \(\times\) 7.5\(-\)DF + W) was 12.7%, equivalent to the sum of combined reductions from double-flange corrosion (9.6%) and web corrosion (3.9%). At the higher \(DOV\) of 13.8%, a similar trend was observed. The strength reductions due to single-flange corrosion (H11.5 \(\times\) 7.5\(-\)SF) and double\(-\)flange corrosion (H11.5 \(\times\) 7.5\(-\)DF) were 9.1% and 17.8%, respectively, with the latter almost twice as significant as the former, as depicted in Figure 7a. Furthermore, web corrosion (H11.5 \(\times\) 7.5\(-\)W) resulted in a strength reduction of 6.5%. Concerning the combined corrosion patterns illustrated in Figure 7b, the single-flange combined corrosion (H11.5 \(\times\) 7.5\(-\)SF + W) and double-flange combined corrosion (H11.5 \(\times\) 7.5\(-\)DF + W) exhibited strength reductions of 15.4% and 24.2%, respectively.