## 2 Experimental Program
### Material Properties  
According to the provisions of specification (ISO 6892-1: 2009), the standard specimens with different corrosion degrees were cut from uniform corrosion columns of the same batch, size, and corrosion environment as the test specimens. Each group had eight specimens, with a total of seven groups, and the test results are shown in Table 2. The corrosion degrees were expressed by the corrosion ratio \(D_{\mathrm{w}}\), and the test results were calculated based on the size of non-corroded specimens. The material tensile test was performed by using a universal testing machine (MTS), and the loading rate did not exceed 1.05 mm/min. The tensile fracture mode of non-corroded steel specimen was typical ductile fracture. With the increase of corrosion ratio, the necking phenomenon of corroded specimens  
\begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline
**Specimen ID** & **\(D\)/mm** & **\(t\)/mm** & **\(e\)/mm** & **\(T\)/d** & **\(W_{\mathrm{o}}\)/kg** & **\(W_{\mathrm{1}}\)/kg** & \(D_{\mathrm{w}}\)/(\%)** & \(N^{\prime}\)/\(k\)N** & \(\overline{\gamma}_{\mathrm{M}}\)/(\%) & \(k^{\prime}\)/\(\times\)10\({}^{7}\) & \(\overline{\gamma}_{\mathrm{M}}\)/(\%) & \(\mu\) \\ \hline C0-0 & 89.82 & 4.07 & 0 & 0 & 9.02 & 9.02 & 0 & 391.5 & — & 13.73 & — & 1.59 \\ C0-30 & 89.74 & 4.28 & 0 & 30 & 9.41 & 8.96 & 4.78 & 377.9 & 3.47 & 13.09 & 4.63 & 1.35 \\ C0-90 & 89.10 & 4.44 & 0 & 90 & 9.44 & 8.87 & 6.04 & 363.8 & 7.08 & 12.12 & 11.71 & 1.47 \\ C0-180 & 89.00 & 4.24 & 0 & 180 & 8.83 & 7.59 & 13.99 & 313.3 & 19.97 & 11.27 & 17.92 & 1.62 \\ C0-270 & 89.06 & 4.01 & 0 & 270 & 8.65 & 7.15 & 16.81 & 295.6 & 24.50 & 10.28 & 25.13 & 1.47 \\ C0-360 & 89.30 & 4.15 & 0 & 360 & 8.48 & 6.77 & 20.22 & 316.8 & 19.08 & 11.12 & 19.02 & 1.75 \\ C15-0 & 89.80 & 4.01 & 15 & 0 & 8.90 & 9.80 & 0 & 239.8 & — & 9.72 & — & 4.45 \\ C15-30 & 89.36 & 3.98 & 15 & 30 & 8.77 & 8.45 & 3.65 & 238.1 & 0.71 & 9.36 & 3.66 & 3.83 \\ C15-90 & 89.04 & 4.1 & 15 & 90 & 8.54 & 7.97 & 6.67 & 217.8 & 9.17 & 9.39 & 3.40 & 4.39 \\ C15-180 & 89.02 & 4.2 & 15 & 180 & 8.50 & 7.38 & 13.23 & 191.6 & 20.10 & 7.25 & 25.42 & 3.24 \\ C15-270 & 89.20 & 4.18 & 15 & 270 & 8.49 & 6.89 & 18.85 & 191.7 & 20.06 & 7.28 & 25.10 & 2.80 \\ C15-360 & 89.22 & 4.12 & 15 & 360 & 8.42 & 6.76 & 19.66 & 181.3 & 24.40 & 8.18 & 15.82 & 5.01 \\ C35-0 & 89.60 & 3.86 & 35 & 0 & 8.73 & 8.73 & 0 & 152.4 & — & 6.39 & — & 7.17 \\ C35-0 & 89.78 & 4.03 & 35 & 30 & 8.97 & 8.65 & 3.56 & 166.7 & -9.38 & 6.20 & 2.98 & 6.62 \\ C35-90 & 89.84 & 4.43 & 35 & 90 & 9.01 & 8.52 & 5.49 & 170.5 & -11.88 & 6.02 & 5.81 & 6.11 \\ C35-180 & 89.08 & 4.41 & 35 & 180 & 8.65 & 7.16 & 17.17 & 143.1 & 6.10 & 4.96 & 22.49 & 5.71 \\ C35-270 & 89.60 & 3.93 & 35 & 270 & 8.58 & 7.12 & 17.12 & 140.5 & 7.81 & 5.00 & 21.80 & 7.58 \\ C35-360 & 89.16 & 4.07 & 35 & 360 & 8.52 & 6.72 & 21.12 & 133.8 & 12.20 & 4.28 & 33.03 & 5.77 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Geometric parameters and test results of specimens.  
obviously weakened, and the steel fracture gradually changed from ductile fracture to brittle fracture. The tensile fracture morphology of specimens is shown in Figure 2.  
The relationships of corroded steel between \(D_{\rm w}\) and \(f_{y},f_{\rm u}\), \(E\), and \(\psi\) were established by linear regression with the least square method, as shown in Equation (2). It can be found that, with the increase of corrosion degree, the mechanical properties of the corroded steel decrease significantly, and the degradation law of each parameter has a linear relationship with the corrosion ratio.  
\[\left\{\begin{array}{l}f_{y}^{\prime}/f_{\rm y}=1-1.1115D_{w}\\ f_{u}^{\prime}/f_{\rm u}=1-0.9981D_{w}\\ E_{\rm s}^{\prime}/E_{\rm s}=1-1.1617D_{w}\\ \delta^{\prime}/\delta=1-1.6014D_{w}\end{array}\right. \tag{2}\]  
where \(f_{\rm y},f_{\rm u}\), \(E\), and \(\psi\) as well as \(f^{\prime}{}_{y},f^{\prime}{}_{u}\), \(E^{\prime}\), and \(\psi^{\prime}\) are the yield strength, tensile strength, elasticity modulus, and percentage elongation of no-corroded and corroded steel, respectively.