# Study on the Load-Bearing Behavior of Underground Steel Structures with Pitting Corrosion Damage
## 6 Comparative Analysis of Simulated Pitting Damage Compression and Three-Point Bending Test Results  
By analyzing the influence of pitting damage on the failure mode, bearing capacity, and deformation capacity of I-steel members under compression and three-point bending loading, it is found that the same pitting damage distribution type has a great influence on the compression and three-point bending test results, and the different pitting damage distribution type has a great influence on the test results under the same loading condition.  
Figure 14: Comparison of five groups of load–mid-span deflection curves in three-point bending test.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample Number** &
\begin{tabular}{c} **Yield Load Py** \\ **(kN)** \\ \end{tabular} & **Yield Displacement Ay (mm)** & **Ultimate Load Pu (kN)** & **Ultimate Displacement Au (mm)** \\ \hline BEND-S & 559.30 & 7.63 & 796.98 & 22.95 \\ BEND-PIT-I & 556.68 & 7.87 & 777.77 & 22.69 \\ BEND-PIT-II & 544.09 & 7.79 & 694.82 & 17.74 \\ BEND-PIT-III & 480.80 & 6.84 & 673.10 & 19.54 \\ BEND-PIT-IV & 448.88 & 5.34 & 652.44 & 15.51 \\ \hline \hline \end{tabular}
\end{table}
Table 3: Characteristic points in the test results of the three-point bending specimen.  
From the perspective of failure modes, in the simulated pitting damage compression test, both the components with pitting damage and those without pitting damage experienced web-buckling failure modes, indicating that pitting damage did not alter the failure mode of the compression test. In the simulated pitting damage three-point bending test, the components without pitting damage ultimately exhibited failure modes related to the local buckling of the compressed flange and local buckling of the web near the loading point. For the components with pitting damage, the final failure mode was characterized by local buckling of the compressed flange and bending failure of the tensile flange. Pitting damage significantly changed the bending failure mode.  
From the perspective of bearing capacity, in the simulated pitting damage compression test, under the same failure mode, the yield load and ultimate load of the four types of pitting damage specimens all decreased to varying degrees, among which the yield load and ultimate load of the inclined pitting damage decreased the most. In the simulated pitting damage three-point bending test, the failure mode changed, and the yield load and ultimate load of the joint load of the joint load and ultimate load of the inclined pitting damage decreased the most.  
From the perspective of deformation capacity, in the simulated pitting damage compression test, under the same failure mode, the yield displacement and ultimate displacement of the four types of pitting damage specimens all decreased to varying degrees. Among them, the yield displacement of the horizontally arranged pitting damage decreased and the ultimate displacement of the vertically arranged pitting damage decreased the most. In the simulated pitting damage three-point bending test, the failure mode changed. The yield displacement and ultimate displacement of the horizontally and vertically arranged pitting damage specimens did not show a significant decrease, while the specimens with triangular and inclined pitting damage showed a significant decrease. Moreover, the inclined pitting damage specimens had the highest decrease in both yield displacement and ultimate displacement.