Mega columns with several reinforced steel profiles – Experimental and numerical investigations

Abstract

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. Current design code like EN 1994-1-1 (EN 1994-1-1, 2004 [1]) (limited to one single encased profile), while AISC 360-16 (ANSI/AISC 360-16, 2016 [2]) allows the design of composite sections with two or more encased sections, although the way to perform such design is not detailed. To understand better the structural behaviour of such composite mega columns and provide a easy to use design method, a two-phase experimental campaign was conducted on scaled isolated steel reinforced concrete (ISRC) columns. Phase 1 of the study includes six 1/4-scaled ISRC columns under static loads: every two of the specimens are loaded statically with the eccentricity ratio of 0, 10%, and 15%, respectively. Phase 2 of the study includes four 1/6-scaled ISRC columns under quasi-static loads: every two of the specimens were loaded under simulated seismic loads with the equivalent eccentricity ratios of 10% and 15%, respectively. A finite element analysis was conducted as a supplement to the physical tests to provide a deeper insight into the behaviour 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 1994–1-1. The validation of the method is made using experimental and numerical results.