Innovative shear transfer system for Concrete Filled Steel Tubes (CFST) in columns

Abstract

The common failure mode of composite steel-concrete structural elements, such as composite columns, generally occurs due to the relative slipping or separation of the steel sheet and the concrete. This leads to materials overspending and low resistance. In the case of beam-to-column joints, the most common solution used in composite construction is introducing a perpendicular gusset plate, which is complex in terms of execution. On the other hand, there is no efficient solution for shear transferring along the whole length of the column to prevent slip under bending. The UPC patent improves very significantly the shear transferring between steel and concrete, enough to achieve the permanent connection in many cases, by means of generating a series of many crown-shaped breakages produced by punching in the profiling stage, not only in the joints but also in the whole length. When the concrete sets, the said breakages embedded therein have the function of resisting shearing forces generated between both materials. It has been successfully applied to composite slabs and, in terms of composite columns, it is also a disruptive innovation to solve the current shear transfer limitation. Besides, this innovative system is easy to be massively produced avoiding the complexities of the conventional beam-to-column joints and reducing the construction costs, especially in high-rise buildings. The aim of this paper is to present this new technology for connecting steel sheet and concrete in CFST columns.