Numerical study of the behaviour of partially concrete- filled cold-formed steel columns, under simultaneous loading of static axial compressive load and axial impact loading

Concrete-filled tubular (CFT) steel columns are a group of composite sections that are considered due to their higher load-bearing capacity, good ductility and good strength. These sections are widely used in a variety of high-rise buildings, offshore structures, subway stations and bridge piers. Therefore, these structures may be exposed to dynamic loads such as axial impact loads (due to accidents or intentional impacts such as falling and releasing various devices, military or terrorist activities). One of the most important techniques in the application of CFT columns is the use of partially concrete-filled steel columns, which are now available due to their cost-effectiveness and weight reduction of the structure, especially in bridge piers and docks. Due to the increasing use of partially concrete-filled steel columns in various structures, it is necessary to know their behavior against axial impact loading, which has not been considered to date. In this paper, the dynamic response of partially concrete-filled cold-formed steel columns against simultaneous loading of static axial compressive load and axial impact load using finite element modeling in ABAQUS software by performing nonlinear dynamic analysis are discussed. Parametric studies to investigate the effects of impact speed, the ratio of the height of the filled concrete to the total height of the column, the height of the impact hammer falling, the ratio of the impact mass to the total mass of the column, the ratio of static axial compressive load and eccentricity of axial impact load are performed. The desired columns have rectangular cross section. The results of this study show that with increasing the parameters of static axial compressive load, filling ratio, eccentricity of axial impact load and the height of the impact hammer falling, the impact load decreases. Also, with increasing the mass ratio and impact speed, the impact load increases.