Optimal economic design of unprotected circular concrete-filled steel tubular columns at ambient temperature and under fire condition

摘要

This paper presents the results of a global comparison between three types of circular columns:rnsteel hollow sections, plain concrete-filled steel tubular columns and reinforced concrete-filled steel tubularrncolumns, submitted to static loads and attending to fire resistance capacity and economic aspects. The analysis isrnfocused on simple columns taking into account the models of Eurocode 3 and 4 to verify the column capacity.Thernautomatic implementation of the algorithms allows achieving a high amount of case studies, covering the realisticrnpossibilities of building columns: with different combinations of geometry (D,t,L), materials (fay, fck, fsy), barrnreinforcement and axial load (NEd). Design curves are presented for optimum values of the thickness, diameter,rnsectional aspect ratio (diameter to thickness), reinforcement, resistance of the materials and fire requirementsrnfor various load level and column lengths. Thin-walled columns and high strength concrete (with the limitationsrnimposed by Eurocode 4) provide the optimal economic solution of the problem.