Modeling Cyclic Axial Response of Cold-Formed Steel Members Including Local Buckling
A modeling approach for simulating steel axial cyclic response including local buckling deformations is in development. Two methods are proposed – (1) a nonlinear spring model with concentrated nonlinear axial load-displacement (P-δ) behavior, and (2) a nonlinear beam-column with distributed nonlinear section axial load-strain (P-ε) behavior (Fig. 1). The models are implemented in OpenSees using Pinching4 as the underlying material model with parameters derived as a function of the dissipated energy, member slenderness, and buckling half-wavelength. Parameter relationships have been shown by recent lipped C- section cold-formed steel cyclic experiments and finite element simulations [1-4]. The presented models would provide means to explore limit states associated to thin-walled member behavior and its application to light steel framed building systems (e.g., shear wall in Fig. 1a).
The proposed methodology is established for thin-walled cold-formed steel members, however the Pinching4 parameters are posed generally as a function of member slenderness and could be extend-ed to hot-rolled steel members and cross-sections with future validation.
David A. Padilla-Llano, Cristopher D. Moen and Matthew R. Eatherton Virginia Polytechnic Institute and State University (Virginia Tech) Blacksburg, VA