Fire design method for bar-reinforced circular and elliptical concrete filled tubular columns

Abstract

A method for calculating the design axial buckling load in the fire situation of unreinforced axially loaded concrete filled circular hollow section columns was presented by the authors in a previous paper [1]. In the present paper, the method is extended to bar-reinforced columns of circular and elliptical cross-section, as a necessary continuation to complete the proposal. The method presented here is based on the guidelines of Clause 4.3.5.1 in Eurocode 4 Part 1.2 for the fire design of composite columns and is developed on the basis of the results of new parametric studies, with varying values of the outer diameter of the column, steel tube wall thickness, relative slenderness, percentage of reinforcement and fire exposure time. From the results of these parametric studies, appropriate expressions and tables for the different parts which integrate the design method are derived. The proposed method is valid for centrally loaded bar-reinforced circular and elliptical concrete filled tubular columns, with a maximum percentage of reinforcement of a 5% and makes allowance for columns with a high slenderness, extending the current limits of Eurocode 4 Part 1.2.