Ninth International Conference on Advances in Steel Structures (ICASS’2018) 5-7 December 2018 - Hong Kong, China Proceedings of the ninth international conference on Advances in Steel Structures Edited by Siu-Lai Chan, Tak-Ming Chan and Songye Zhu. Copyright © 2018 by The Hong Kong Institute of Steel Construction. A GENERAL FORMULATION FOR THE STABILITY DESIGN OF STEEL MEMBERS Trayana Tankova 1 *, Luís Simões Da Silva 1 And Liliana Marques 1 1 ISISE, Department of Civil Engineering, University of Coimbra E-mails: ttankova@uc.pt, luisss@dec.uc.pt, lmarques@dec.uc.pt Abstract: In this paper, a new general formulation for stability design of steel columns, beams and beam-columns with variable geometry, loads and supports is proposed. The verification is based on buckling mode conform shape of the initial imperfection with an amplitude previously calibrated for the standard prismatic simply-supported columns and beams in Eurocode 3. It avoids the calibration of additional factors because it is applied as an interaction equation and the first and second order contributions to the longitudinal stress utilization are added for each cross-section along the member length. The paper summarizes the general formulation for design of steel members in a universal format covering any buckling mode. Several aspects regarding the member behaviour in the context of a specific buckling mode are discussed and finally, validation of the approach is carried out to show its consistency and accuracy. Keywords: Steel; Stability; General Formulation; Eurocode 3; Stability Design DOI: 10.18057/ICASS2018.P.136 1 INTRODUCTION Steel structures provide efficient and sustainable solutions due to the material characteristics, namely low cost and recycling potential. However, due to the high strength-to-weight ratios an optimum structural design leads to slender structural members such as columns, beams and beam-columns. The design codes available nowadays [1] provide procedures for the stability design members which are commonly based on a reference case: a pin-ended prismatic member subject to a concentrated axial force and/or a constant bending moment. For the reference cases, elastic second-order stresses are derived, exactly or in an approximate way, considering initial geometrical imperfections that satisfy the boundary conditions. For the loading and boundary conditions considered, the critical cross-section where the maximum stress is reached occurs at mid-span. The resistance of the member is reached using a first yield failure criterion for the maximum combined first and second-order stresses. The influence of the variation of the material and geometrical properties, as well as member imperfections is contemplated in a semi- empirical way by statistical adjustment of the amplitude of the initial geometrical imperfection based on experimental evidence. This calibrated amplitude depends on the cross-section type, buckling mode, steel grade and thickness of the plates making up the cross-section and is expressed as a generalized imperfection () that explicitly varies linearly with the normalized slenderness of the member ( ̅ ).