08.07: Performance and capacity of composite “mega columns” with encased hot rolled steel sections

Steel reinforced concrete (SRC) columns are widely used in high-rise buildings, since they provide larger bearing capacity and better ductility than traditional reinforced concrete (RC) columns. This type of structural system is not currently explicitly addressed in the actual design codes. The paper aims at presenting the behaviour of a new configuration of mega columns – isolated steel reinforced concrete (ISRC) columns. A two-phase test was conducted on scaled ISRC columns designed based on a typical mega column of a super high-rise building. 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 (FEA) was conducted as a supplement to the physical tests to provide a deeper insight into the behaviour of “mega columns”. An extended Plastic Distribution Method is defined to evaluate the capacity of the specimens. The method is based on simplifications similar to those proposed in EC4 [1]. The scope of this latter standard is limited to the consideration of one single steel profile. The method is validated by comparisons with experimental and with numerical simulation results using advanced finite element programs, showing a good accuracy in results.