## 2 Retrofitting Test on Steel Angles
### Test Program  
The loading points of all specimens (reinforced and unreinforced) in this test are located at the centroid of the steel angle, and the steel plates used for reinforcement do not directly bear the load. To meet the boundary conditions of the hinge joint at both ends, the test piece adopts bidirectional knife hinge supports at both ends. The hinge supports are placed in the same direction as the symmetrical axis of the steel angle, ensuring that the end of the test piece can rotate freely around the x\({}_{0}\) and y\({}_{0}\) axes of the steel angle, as shown in Figure 3. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline \multirow{2}{*}{**Type**} & \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Slenderness**} & \multicolumn{2}{c}{**Width of**} & \multicolumn{2}{c}{**Length of**} & \multirow{2}{*}{**Retrofitting**} & \multirow{2}{*}{**Clamp Type**} \\  & & **Ratio** & & **Reinforcement** & & & \\  & & & **Plate/mm** & & **Plate/mm** & & \\ \hline \multirow{6}{*}{L125 \(\times\) 10} & LS3-1-1 & 90 & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) \\  & LR3-1-1 & 90 & 168 & 2212 & 500 & Double-bolt \\  & LR3-1-2 & 90 & 168 & 2212 & 700 & Double-bolt \\  & LS3-2-1 & 110 & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) \\  & LR3-2-1 & 110 & 168 & 2718 & 500 & Double-bolt \\  & LR3-2-2 & 110 & 168 & 2718 & 700 & Double-bolt \\  & LR3-2-3 & 110 & 168 & 2718 & 700 & Single-bolt \\  & LR3-2-4 & 110 & 168 & 2718 & 1000 & Double-bolt \\ \hline \multirow{6}{*}{L160 \(\times\) 12} & LS4-1-1 & 90 & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) \\  & LR4-1-1 & 90 & 193 & 2852 & 500 & Double-bolt \\  & LR4-1-2 & 90 & 193 & 2852 & 700 & Double-bolt \\  & LS4-2-1 & 110 & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) \\  & LR4-2-1 & 110 & 193 & 3488 & 500 & Double-bolt \\  & LR4-2-2 & 110 & 193 & 3488 & 700 & Double-bolt \\  & LR4-2-3 & 110 & 193 & 3488 & 700 & Single-bolt \\ \hline \multirow{6}{*}{L180 \(\times\) 14} & LS5-1-1 & 90 & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) \\  & LR5-1-1 & 90 & 207 & 3203 & 700 & Double-bolt \\  & LR5-1-2 & 90 & 207 & 3203 & 1500 & Double-bolt \\  & LS5-2-1 & 110 & \(\backslash\) & \(\backslash\) & \(\backslash\) & \(\backslash\) \\  & LR5-2-1 & 110 & 207 & 3917 & 700 & Double-bolt \\  & LR5-2-2 & 110 & 207 & 3917 & 700 & Single-bolt \\  & LR5-2-3 & 110 & 207 & 3917 & 1000 & Double-bolt \\ \hline \hline \end{tabular}
\end{table} 
Table 1: _Cont._  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Type**} & **Yield** & **Ultimate** & **Elastic** & & \\  & **Strength** & **Strength** & **Modulus** & **Poisson’s** & **Ratio** & **Elongation/\%** \\  & **(\(\mathbf{y}_{y}\))/MPa** & **(\(\mathbf{f}_{u}\))/MPa** & **(\(\mathbf{E}_{s}\))/GPa** & & **Ratio** & **Elongation/\%** \\ \hline L80 \(\times\) 7 & 396 & 535 & 199.6 & 0.282 & 27.4 \\ L100 \(\times\) 8 & 378 & 527 & 205.1 & 0.289 & 27.3 \\ L125 \(\times\) 10 & 384 & 531 & 205.3 & 0.287 & 26.6 \\ L160 \(\times\) 12 & 383 & 539 & 201.3 & 0.296 & 27.2 \\ L1 Static loading is carried out by a hydraulic testing machine. Prior to the test, a numerical analysis of the components is carried out to obtain simulated values of the ultimate bearing capacity of the components, which are used as estimated values for the test loading. The loading system is divided into two stages. The first stage adopts a vertical force control loading method, which is applied step by step. Each level of load takes 5% of the estimated ultimate load until it reaches 80% of the estimated ultimate load and then moves on to the second stage. The second stage adopts a vertical displacement-controlled loading method with a loading rate of 0.1 mm/min. The failure sign is that after the load-displacement curve of the specimen crosses the peak point, the bearing capacity decreases to 65% of the peak load, and then the loading ends.