Experimental Research on Seismic Performance of Partially-Encased Steel-Concrete Composite Columns with Cross-Shaped Sections

Experimental investigations were conducted on three partially-encased composite steel-concrete column specimens with cross-shaped sections （short for cross-shaped PEC columns） under constant vertical load and cyclic horizontal loading. The specimens consisted of one PEC column with a main steel component （MSC） of solid web steel （short for SWS cross-shaped PEC column） and two PEC columns with MSCs of honeycomb steel （short for HS cross-shaped PEC columns） having different axial compression ratios. The effects of the MSC web opening and the axial compression ratios on the seismic performance of cross-shaped PEC columns were investigated. The results showed that the failure characteristics of the PEC columns were concrete crushing accompanied by elastic-plastic buckling of the compression flange， ultimately leading to a compression-bending failure mode. The load-displacement hysteresis curves of the column specimens were full， and the hysteresis loops under different cycle numbers at the same loading stage （same amplitude） were nearly identical， indicating that the PEC columns exhibited good energy dissipation capacity and bearing capacity stability.The bearing capacity， elastic lateral stiffness， ductility， and energy dissipation capacity of the SWS cross-shaped PEC column were higher than those of the HS cross-shaped PEC columns under the same axial compression force. With the increase in axial compression ratio， the bearing capacity and lateral stiffness of HS cross-shaped PEC columns increased， but the ductility and deformation capacity decreased significantly， and the energy dissipation capacity also decreased. The full-section plasticity theory could effectively predict the bearing capacity of the cross-shaped PEC columns under uniaxial bending.