Seismic behavior of square high-strength concrete columns

Results of a study investigating flexural capacity and ductility of square high-strength concrete columns are presented. As part of the investigation, nine test columns were subjected to constant axial load and cyclic lateral loads. It is concluded that high-strength concrete columns subjected to axial load levels below 20 percent of their axial load capacity and designed based on the seismic provisions of American Concrete Institute (ACI) 318-89 have sufficient ductility. However, the ACI 318-89 code provision overestimates flexural capacity of high-strength concrete columns subjected to both axial and bending moment, even columns with confining steel, as required by seismic provisions of the code. Modifications to be incorporated into ACI 318-89 to calculate conservatively the flexural capacity of high-strength concrete columns are suggested.