Mega columns with several reinforced steel profiles experimental and numerical investigations

Steel reinforced concrete (SRC) columns are widely used in super high-rise buildings, since they can provide larger load bearing capacity and better ductility than traditional reinforced concrete (RC) columns. Six concrete encased composite columns were designed based on a typical mega-column of a super high-rise building constructed in China. The specimens are identical in geometrical configurations having as changing parameter the eccentricity ratio of the applied load: every two of the specimens were loaded statically with the eccentricity ratio of 0,10%, and 15%, respectively. Such columns are however not covered by EN 1994-1-1[2] (limited to one single encased profile), while AISC360-16[8] allows the design of composite sections built-up with two or more encased steel sections, although the way to perform such a design is not detailed.A finite element analysiswas conducted as a supplement to the physical tests to provide a deeper insight into the behavior of SRC columns. The experimental campaign has yielded stable test results, suggesting a desirable performance of SRC columns. It is concluded from these experiments that sufficient composite action exists between the concrete and the steel sections for the tested SRC specimens, and that the current code provisions are applicable for the considered configuration, in predicting the flexural capacity of SRC columns when the eccentricity ratio is less than or equal to 15%.The present paper summarizes the principles and an application method for the design of such columns under combined axial compression and bending. The method is based on simplifications provided in EN 1994–1. The validation of the method is made using experimental and numerical results. (Author)