## 2 Experimental Study  
### Specimen Design  
As shown in Figure 1, a total of eight large-scale specimens with different parameters were designed and tested to explore the influence of parameters such as section dimension, length ratio, and stiffener spacing on the seismic performance of links. The designed parameters of the links are summarized in Table 1. The flanges and web were welded by complete-joint-penetration (CJP) groove welds [39; 40; 41]. Both the link flange and the web satisfied the provisions for highly ductile members according to the AISC 341-10 standard (AISC 2010a) [42]. In this test, the influence of the cross-sectional shape and length of the link on its energy dissipation capacity was considered. A range of link lengths were tested, ranging from short shear yielding links to very long flexural yielding links. In other words, the classification was based on the normalized link length and thus the length ratio was introduced to define the following:  
\[\zeta=eV_{\mathrm{P}}/M_{\mathrm{P}}, \tag{1}\]  
where \(M_{\mathrm{P}}\) is the plastic flexural strength and \(V_{\mathrm{P}}\) is the plastic shear strength. Links with a length ratio of less than 1.6 were dominated by shear yielding, whereas those above 2.6 were dominated by flexural yielding. Between these limits, link inelastic response was heavily influenced both by shear and flexure. The link beam stiffeners were welded to the link web and to both link flanges using fillet welds, which were set on one side of the web only. The stiffeners were designed with a thickness of 10 mm and a spacing of 150 mm and 200 mm. According to the requirement stated in AISC 341-10, the intermediate web stiffeners were spaced at intervals not exceeding (30\(t_{w}\)-d/5), where \(t_{w}\) denotes the thickness of web and d is the beam depth. The stiffener spacing for the link beams of all specimens satisfied this limit. The vertical fillet welds of the web stiffeners were terminated at a distance of no less than five times the web thickness from the flange-to-web weld in order to delay web fracture at the region where the flange-to-web CJP groove weld and the fillet welds of the stiffeners met. Specimens L3, L4, L5, L7, and L8 were treated using welding access holes and Specimens L1, L2, and L6 were not treated using welding access holes (see Figure 2). Figure 1: Experimental specimens. (**a**) L1; (**b**) L2; (**c**) L3; (**d**) L4; (**e**) L5; (**f**) L6; (**g**) L7; (**h**) L8. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Number** & **Section Dimension/mm** & **Length** & **Number of** & **Stiffener** & **Length Ratio** \\  & & **/mm** & **Stiffeners** & **Spacing** & **\& **\& \\ \hline L1 & H350 \(\times\) 175 \(\times\) 7 \(\times\) 11 & 900 & 5 & 200 & 1.43 \\ L2 & H250 \(\times\) 125 \(\times\) 6 \(\times\) 9 & 800 & 4 & 200 & 1.84 \\ L3 & H250 \(\times\) 125 \(\times\) 6 \(\times\) 9 & 700 & 3 & 200 & 1.61 \\ L4 & H250 \(\times\) 125 \(\times\) 6 \(\times\) 9 & 700 & 5 & 150 & 1.61 \\ L5 & H350 \(\times\) 175 \(\times\) 7 \(\times\) 11 & 700 & 3 & 200 & 1.11 \\ L6 & H350 \(\times\) 175 \(\times\) 7 \(\times\) 11 & 700 & 4 & 200 & 1.11 \\ L7 & H350 \(\times\) 175 \(\times\) 7 \(\times\) 11 & 700 & 5 & 150 & 1.11 \\ L8 & H350 \(\times\) 175 \(\times\) 7 \(\times\) 11 & 600 & 3 & 150 & 0.95 \\ \hline \hline \end{tabular} Note: L3, L4, L5, L7, and L8 were treated using welding access holes; L1, L2, and L6 were not treated using welding access holes.  
\end{table} 
Table 1: Parameter design of each test specimen. Figure 2: Welding access hole treatment. (**a**) L1, L2, and L6; (**b**) L3, L4, L5, L7, and L8. The links and end plates were made of Q235 steel (nominal yield strength \(f_{y}\) = 235 MPa), and other components were made of Q345 steel (\(f_{y}\) = 345 MPa). Table 2 lists the material properties for the link steel measured by tensile coupon tests. The parameters of each specimen of the elastic modulus \(E\), the yield strength \(f_{y}\), the ultimate strength \(f_{u}\), and the elongation \(\delta\) were obtained.