Investigation of geometric nonlinear behavior of multistory steel structures with incremental and practical second-order analysis methods

In addition to vertical loads, horizontal loads such as earthquake and wind loads lead to form second order effects together with large displacements influencing the structural behavior. In these cases, it is important to use calculation methods that consider the second order effects in analyses. In this study, second order analyses are performed by utilizing incremental and practical methods on steel structure systems. In this work, incremental methods such as single-step incremental, Newton-Raphson, modified Newton-Raphson and practical methods such as iterative vertical load, direct P-Delta, Li, King-Chen, addition of fictitious diagonal member and addition of fictitious column member are used. Story drift, member end moments and overall drift index obtained from incremental and practical second order analyses conducted on numerical applications are investigated together with the reference study and the results of utilized calculation methods are comparatively evaluated. According to the relative difference ratio obtained by comparing the results derived from both second order analysis methods and reference study, it is determined that the results have adequate sensitivity. In order to investigate the performance of braced steel systems used in the study, concentrically braced steel systems with various geometric forms were generated and the variation of slenderness ratio, overall drift index, story drift and internal force values were determined. In accordance with the results, concentrically braced steel systems with various geometric forms efficiently limited the overall story drift, inter-story drift and overall drift index values.