Extension of the Zone Method of Eurocode 2 for reinforced concrete columns subjected to standard fire

Purpose - The purpose of this paper is to develop a method suitable for the design of reinforced concrete columns subjected to a standard fire. Design/methodology/approach - The Zone Method - a "simplified calculation method" included in Eurocode 2 - has been developed by Hertz as a manual calculation scheme for the check of fire resistance of concrete sections. The basic idea is to disregard the thermal strains and to calculate the resistance of a cross-section by reducing the concrete cross-section by a "damaged zone". It is assumed that all fibers can reach their ultimate, temperature dependent strength. Therefore, it is a plastic concept; the information on the state of strain is lost. The calculation of curvatures and deflections is thus only possible by making further assumptions. Extensions of the zone method toward a general calculation method, suitable for the implementation in commercial design software and using the temperature dependent stress-strain curves of the Advanced Calculation Method, have been developed in Germany. The extension by Cyllok and Achenbach is presented in detail. The necessary assumptions of the Zone Method are reviewed, and an improved proposal for the consideration of the reinforcement in this extended Zone Method is presented. Findings - The principles and assumptions of the Zone Method proposed by Hertz can be validated. Originality/value - An extension of the Zone Method suitable for the implementation in design software is proposed.