## 2 Experimental Study
### Test Setup, Instrumentation, and Loading Protocol  
Figure 2(a) shows the test setup. The link specimen was securely clamped to two steel frame beams designed with large stiffness to simulate the constraint of adjacent frame beams to the link. A shear force was applied perpendicularly to the link to ensure both ends of the link were subjected to equal bending moments in opposite directions. The details of setup connection are as follows: the loading frames that measured 500 mm \(\times\) 600 mm \(\times\) 40 mm \(\times\) 30 mm were arranged on one side of the frame beams measuring 500 mm \(\times\) 300 mm \(\times\) 12 mm \(\times\) 30 mm, respectively. Besides the connections of the four high-strength tie rods between the loading beam and the frame beam, both their ends were connected to the end plates measuring 588 mm \(\times\) 300 mm \(\times\) 24 mm through a row of seven 10.9-class M26 high-strength bolts, and some box pads were placed between them. In addition, a load cell was pinned to the jack at one end and pinned to the left hinge support at the other hand. They were arranged between the left reaction frame and the left loading frame. The right hinge support was pinned to the right loading frame at one hand and was pinned to the right reaction frame at the other hand. The loading site is shown in Figure 2(b). A row of rollers that could slide horizontally was added at the bottom of the lower frame beam to ensure the sliding of the bottom frame beam during the test (see Figure 2(c)). At the same time, the rollers were smeared with lubricant to reduce friction.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Type**} & **Yield Strength** & **Ultimate Strength** & **Elastic Modulus \(E\)/10\({}^{5}\)** & **Elongation** \\  & \(f_{y}\)/MPa & \(f_{u}\)/MPa & MPa & **8/\%** \\ \hline
**Web** & 271.00 & 430.00 & 1.93 & 30.66 \\
**Flange** & 261.13 & 436.25 & 2.00 & 24.96 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Specim material properties.  
Instrumentation was used to measure the load, displacements, and strains of the specimen. The strain gauge and the strain rosette were mounted reasonably on the link and the frame beam by electric measurement to measure the strains of both links and beam segments (see Figure 4). In addition, the displacement was measured by a displacement meter. Figure 5 gives the arrangement of the displacement measuring points; among them, the points 1, 2, and 3 use pull-line displacement meters and the rest use resistance strain gauges. In this test, the DH3816 was used to collect the data from the strain gauge and the strain rosette. The tester could effectively control the loading process and use the system to collect the displacement on the pull-line displacement sensor through the DH5922N dynamic data acquisition system.  
Figure 3: Experimental setup. (**a**) Details of test setup; (**b**) Photo; (**c**) Roller.  
Figure 6 shows the cyclic loading pattern of the test. The displacement, \(\Delta_{y}\), only considered applying a horizontal cyclic reciprocating load to the link, and adopted a displacement control loading method. It was loaded step by step according to the multiple of the yield displacement \(\Delta_{y}\) of the link in the constant-width loading system as follows: 0, \(\Delta_{y}\), 0, \(-\Delta_{y}\); 0, 2\(\Delta_{y}\), 0, \(-\Delta_{y}\); 0, 3\(\Delta_{y}\), 0, \(-\)3\(\Delta_{y}\)..., and the specimen was loaded until complete failure.  
Figure 4: The measurement arrangement of strain gauge and strain rosette.  
Figure 5: The measurement arrangement of displacements.  
Figure 6: Loading history for the cyclic loading test.