Impact of Local Geometric Imperfections on Steel Columns Under Combined Axial and Lateral Cyclic Loading

Steel sections are usually manufactured with geometric defects and deviates from the original ideal shape during rolling process; these defects are called imperfection in international standards. This study is devoted towards investigating local geometric imperfections of steel columns under combined effect of axial load and lateral cyclic displacements which simulates steel columns under seismic events. Ten wide flange sections with two cases for each section: ideal and imperfect. A comprehensive nonlinear finite element model which is validated against available experimental data in literature was employed. A sustained axial load which ranges from 20-100 percent of the maximum axial capacity for the column was applied prior to application of the designated lateral cyclic displacement amplitude. It was found that web local imperfection has a substantial impact on the cyclic response of the columns. It was also revealed that higher axial load ratios impact column response than do lower load ratios. Moreover, drift angle was found more susceptible in stocky than in light sections. The study showed that there is a limiting zone within the slenderness ratios for both of flanges and web should be avoided when considering section design of columns under seismic events because it yields a big difference between ideal and imperfect section.