Buckling of stainless steel columns and beams in fire

Abstract

Material properties and their response to elevated temperatures form an essential part of structural fire design. At elevated temperatures, stainless steel displays superior material strength and stiffness retention in comparison to structural carbon steel. Although independently important, the relationship between strength and stiffness at elevated temperature also has a significant influence on the buckling response of structural components. This paper examines existing test results and presents the results of a numerical parametric study, using ABAQUS on stainless steel columns in fire. Sensitivity to local and global initial geometric imperfections, enhancement of corner strength due to cold-work and partial protection of the column ends is assessed. Parametric studies to explore the influence of variation in local cross-section slenderness, global member slenderness and load level are described. Test results are compared with the current design rules in Eurocode 3: Part 1.2, the Euro Inox/SCI Design Manual for Structural Stainless Steel and those proposed by CTICM/CSM. The results of a total of 23 column buckling fire tests, six stub column fire tests and six fire tests on beams have been analysed. Overly conservative results and inconsistencies in the treatment of buckling phenomena and the choice of deformation limits are highlighted. A revised buckling curve for stainless steel in fire, consistent strain limits and a new approach to cross-section classification and the treatment of local buckling are proposed. These revisions have led to a more efficient and consistent treatment of buckling of stainless steel columns and beams in fire. Improvements of 6% for column buckling resistance, 28% for stub column (cross-section) resistance and 14% for in-plane bending resistance over the current Eurocode methods are achieved.