System buckling analysis for multi-story frames subjected to nonconservative forces

Abstract

The evaluation of the effective length factor (K-factor) of columns based on the system buckling approach is a convenient tool in the stability design of multi-story frames. This method is superior to other analytical approaches, such as isolated subassembly and story-based approaches, in that inter-column and inter-story interactions are inherently taken into account. In this study, in order to investigate the effect of nonconservative forces on buckling loads and K-factors for the single-and multistory framed structures, the system buckling approach is presented. For this purpose, the finite element model, based on the Hamilton's principle, is formulated for the stability analysis of framed structures subjected to nonconservative forces. In numerical examples, buckling loads and K-factors for single-and multi-story frames subjected to conservative or nonconservative forces are evaluated and compared with those obtained by other researchers. Especially the effect of the stiffness ratio of girder to column on K-factors is investigated for nonconservative systems.

Story-Based Stability of Multistory Steel Semibraced and Unbraced Frames with Semirigid Connections

“…The beam-to-column rotational stiffness (Z) was randomly selected from zero to 8 Nm/rad via a uniform distribution. Each column-to-ground connection also had its rotational stiffness (Rl,1,j) randomly selected from 10 1 to 12 Nm/rad, with the exponent being uniformly distributed.…”

“…Hellesland (2009) proposed an approximate storey-based analysis method to evaluate the second-order effects relating to column imperfections (which do not affect stability according to Ziemian (2010) and Ma and Xu (2019a)) on the deformations of storeys within multi-storey frames. Finite element analysis and matrix methods have also been proposed by Kim and Choi (2015) and Li et al (2016) for the storey-based analysis of frames, but require matrix-based solutions instead of providing closed-form, explicit solutions. Overall, the idea of decomposing a frame into individual storeys to be analyzed for instability corresponding to zero lateral stiffness is easy to understand but has only been addressed by Liu & Xu (2005), in which the aforementioned shortcomings result in only approximate equations unlike the equations in the proposed method.…”