Numerical analysis for seismic performance of long links in eccentrically braced frames strengthened with additional steel plates and diagonal stiffeners

This paper presents a numerical analysis of the seismic performance of a single conventional long link (AISC-341-16) and four variants of strengthened long links, incorporating additional steel plates and diagonal stiffeners in the EBF system. This study numerically proposes new strengthening techniques that correlate the seismic performance of conventional links with variations in the effective long links. The analysis employs the NASTRAN 2023 finite element approach; the link element is modelled as a fixed shell element with selected nodes at the loading positions allowed to translate along the y-axis. The loading protocol with AISC 341-16 guidelines for link beams. Seismic performance is evaluated in terms of strength, stiffness, ductility, and energy dissipation. The analysis reveals that the fully strengthened LPJT-1-2-3 model (flange thickening + midspan/end stiffeners) achieved an 82.7% increase in strength capacity (181.3 kN ultimate load) and 20.5 N/m initial stiffness, along with superior energy dissipation. However, partial strengthening configurations demonstrated an optimal balance: LPJT-1 and LPJT-1-3 maintained ductility (μ = 14–16). The proposed strengthening method combines 8 mm flange thickening (1/3L) with end-diagonal stiffeners, similar to those used in the LPJT-1 and LPJT-1-3 specimens. This strategy redistributes stresses to the web, delaying flange buckling without compromising ductility.