Some considerations in the design of unprotected concrete-filled steel tubular columns under fire conditions

✍ Scribed by Y.C. Wang

• Publisher: Elsevier Science
• Year: 1997
• Tongue: English
• Weight: 977 KB
• Volume: 44
• Category: Article
• ISSN: 0143-974X
• DOI: 10.1016/s0143-974x(97)00060-6

✦ Synopsis

This paper is concerned with the fire resistant design of centrally loaded unprotected concrete-filled steel tubular columns using Eurocode 4 Part 1.2. It addresses three issues: the column buckling curve to be used for elevated temperature design, the implementation of the calculation method in Eurocode 4 Part 1.2 and the equivalent time of fire exposure. The predicted column fire resistance using the Eurocode 4 Part 1.2 calculation method is compared with the results of tests on 36 concrete-filled circular hollow section columns and seven square hollow section columns conducted at the National Fire Laboratory of Canada. This comparative study indicates that the choice of column buckling curve for elevated temperature design depends on the adopted concrete strength and stiffness-temperature models. If the models in the main text of Eurocode 4 Part 1.2 are used, column bucking curve 'a' seems to give more accurate results. For the standard fire resistant design, this paper proposes a simple method to implement the general calculation method in Eurocode 4 Part 1.2. This proposed method is easy to use and was demonstrated to be quite accurate. Using the parametric time-temperature relationships in Eurocode 1 Part 2.2 to represent the behaviour of realistic fires, this paper studies the equivalent time approach, based on the column resistance. Results from this study show that the equivalent time equation in Eurocode 1 Part 2.2 needs modifying to allow for the inter-dependence between fire load and ventilation factor and this equation is also unsafe. This paper further suggests introducing a multiplication factor in the equivalent time equation to cater for different types of construction element.