Wet concrete loading of thin-walled steel box columns during the construction of a tall building

Abstract

Concrete filled thin-walled steel box columns are currently being increasingly used in the construction and design of tall buildings. These columns provide economy during construction and many other advantages for steel-framed buildings. The most significant factor that concrete filled steel box columns display in reducing the construction cost of a steel framed building is that the external steel box provides permanent and integral formwork for the concrete infill and, thereby, reduces construction, labour and material costs considerably. This paper considers the wet concrete loading of steel box columns used as permanent formwork for concrete filled box columns in tall buildings. A linear folded plate finite element method developed else-where is used to consider the axial loads and hydrostatic loads imposed on a steel box column during construction and wet concrete pumping operations. This paper considers two boundary conditions which model various types of weld configurations and considers the aspect of midspan propping in reducing the lateral deflections. The results of lateral deflections and axial stresses are presented and allowable slenderness limits are developed for various levels of pumping in a tall building. The influence of lateral deflections on the increased volume of concrete is also considered for design and construction purposes and the presence of initial imperfections and residual stresses are also discussed within the paper.