Abstract
The structural damage observed in buildings highlights the crucial need for improved design quality in seismic-resistant construction systems, particularly for steel structures. This necessitates the development of earthquake-resistant structural systems that perform effectively both technically and architecturally. This study investigates the seismic behaviour of long links in Eccentrically Braced Frames (EBFs) strengthened using a hybrid method that combines flange thickening steel plate, and diagonal stiffeners. Five specimens were constructed and tested under cyclic lateral loading according to AISC-341-16 protocols. The specimens include one control link and four variations of flange and web strengthening, which were modified based on previous research. The research aims to propose novel strengthening methods that correlate the seismic performance of conventional structures with variations of the effective long link. Test specimens and experimental setups were designed considering boundary conditions and structural laboratory limitations. Results indicate that the specimens that were strengthened at both ends and mid-span with flange thickening and diagonal stiffeners attained the peak structural load capacity (27.48% increase) and stiffness (28.47% increase). However, its energy dissipation capacity was compromised by the implementation of stiffeners, which constrained plastic zone development. The specimen with only flange thickening demonstrated the highest ductility (1.54) and best energy efficiency (38.90%). Experimental results confirm that the hybrid strengthening technique effectively enhances cyclic performance in long-link EBFs, addressing both strength and ductility requirements in seismic-resistant structures.