Local seismic stability of flanged cruciform sections (FCSs)

• Published in: Engineering structures 2015-08, Vol.96, p.126-138
• Main Authors: Keykhosro Kiani, Babak, Torabian, Shahabeddin, Mirghaderi, Seyed Rasoul
• Format: Article
• Language: English
• Subjects: Beam-columns; Ductility; Flange-cruciform; Nonlinear finite element analysis; Seismically compact
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2015.04.003

•FEM parametric studies on the seismic behavior of flanged cruciform sections.•Plastic rotation capacity of FCSs as a function of the axial load and web slenderness.•Proposing a section-specific P–Mp interaction equation for FCS beam-columns.•Providing a new seismic width-to-thickness limiting ratio for the webs of FCSs. Flanged cruciform sections (FCSs), as an appropriate alternative for column cross-section in orthogonal moment-resisting frames, need more cross-section specific code requirements in design specifications. To extend the specifications for FCSs, local buckling of webs, flexural ductility under axial compression and cyclic bending moments, and also P–MP interaction relationships have been studied. A validated material and geometric nonlinear finite element model in ABAQUS has been used to perform a comprehensive parametric study on FCSs. The modeling protocol includes a new residual stress distribution, as well as appropriate geometric imperfections. A wide range of web depth-to-thickness ratios is considered to evaluate the current AISC-341 seismically compact limit state. As the web slenderness and axial load have significant effects on the cyclic behavior and ductility of the FCS beam-columns, a new web seismically compact limiting ratio is proposed for FCSs as a function of the axial load to provide the desired ductility. It is shown that taking half of the depth in calculating web slenderness of FCSs and using the current I-section web compactness limitations for FCSs, can be non-conservative. The study shows that the AISC-341 and ASCE-41 P–MP interaction curves for beam columns made from wide flange sections are overly conservative when applied to FCSs. A modified interaction curve is proposed which more accurately represents beam column behavior of FCSs.