P 1287 – Concrete-filled steel tubular columns for multistorey buildings – innovation and design
Composite columns are used in building and industrial construction because of their various advantageous properties. On the one hand, columns with smaller cross-sectional dimensions can be realised with high load-bearing capacities at the same time. On the other hand, high fire protection requirements can be implemented relatively easily. This is made possible by the targeted combination of the material properties of steel and concrete, in particular the high strength and stiffness as well as the deformability of steel and the low thermal conductivity of concrete. Concrete-filled steel tube
columns using high-strength materials have the potential to exhibit even greater loadbearing resistances or slimmer column cross-sections and to be competitive.
Within the FOSTA research project ” Concrete-filled steel tube columns in high-rise buildings – Innovation and Design” (IGF project no.: 19677), we were investigating the stability behavior of composite columns using experimental, numerical, and analytical methods. The current version of Eurocode 4, Part 1-1 “Design of composite steel and concrete structures” contains design methods for different types of composite columns.
However, for concrete-filled steel tube columns with a solid steel core and concretefilled double steel tube columns, there are currently no normatively regulated simplified design methods for normal temperatures and fire design. The experimental tests included different cross-sections, steel types and concrete strengths. For the experimental analysis of the cross-section capacity, stub-column tests were carried out. In addition, one-storey (4m) and two-storey (8m) columns with realistic cross-section dimensions were tested to evaluate the use of high-strength materials for practical applications. A numerical model was developed and validated against own and independent test results given in the literature that implies experimental material properties, composite action, geometric imperfections and residual stresses. The model was used to perform a comprehensive numerical simulation study and to analyze the basic mechanical understanding of the composite column. In addition, a finite element model for fire simulations was developed and validated on the basis of external tests, and simulations of the fire behavior under standard temperaturetime curves were carried out with utilization rates relevant to building practice. The experimental and numerical results were used to develop a simplified design proposal within the framework of the second generation of the European design rules. In addition, the scientific basis for a simplified verification procedure for the design of innovative composite columns in case of fire was investigated.
Prof. Dr. sc. techn. habil. M. Knobloch, M.Sc. P. Schurgacz