Effect of Global Geometric Imperfections on the Cyclic Response of Moment Resisting Frame Columns

This paper investigates the impact of explicit initial geometric imperfections on the seismic response of wide flange steel column sections in moment resisting frames. Ten wide-flange sections (five light and five stocky) were chosen in the parametric investigation. The columns were subjected to a combined effect of axial load and lateral cyclic displacement protocol as per ASCE guidelines. Target axial load ranging from 20 to 100 of the column axial capacity was chosen to cover a wide range of axial loads employed in practice. Nonlinear finite element was used to conduct the analyses throughout the paper. The theoretical models were validated against available experimental data. The study indicated that the reduction in the drift angle capacity of the imperfect compared to the straight sections is approximately ranging between 0% and 60% for various axial load ratios. Results has also revealed that the effect of imperfection is more pronounced for stocky steel sections under high axial load ratios, although other sections responded in a variable degrees. Design recommendations were proposed to aid in better simulation of advanced structural analyses.