Modification factor for reliable design of shear link in EBF subjected to high axial force based on Eurocode 8

Abstract

Eccentrically braced frames (EBFs) are widely recognized as effective seismic resisting systems for buildings and other structures due to their high ductility and stiffness. The performance of EBFs heavily relies on the behaviour of the critical component known as the link, which governs the system's ductility, strength, and overall response. While the link is typically subjected to high shear force and bending moment, the significance of axial force in certain EBF configurations has received limited attention in previous studies and design codes. This research aims to investigate the effects of high axial load on the reliability and performance of EBF links using the finite element method. Experimental data is utilized to validate numerical models, ensuring the accuracy of the subsequent reliability analysis. The assessment of link reliability under high axial force is conducted within the framework of Eurocode 8 (EC8), employing the first-order reliability method (FORM). The results demonstrate that EBF links with very short lengths exhibit acceptable levels of reliability. However, as the link length increases, the target reliability index is not met. To address this challenge, a modification factor is proposed based on the Rackwitz–Fiessler iterative procedure, enabling adjustments to the link shear design. Furthermore, a sensitivity analysis is performed to evaluate the influence of random variables on the reliability analysis. © 2025 Institution of Structural Engineers