Simplified numerical model development for sophisticated analysis of lightweight-concrete encased cold-formed steel compressed column-end joints and panels

Abstract

Since cold-formed steel (CFS) members are prone to complex buckling phenomena; that decrease their structural capability, many strengthening trends have been developed so far. One of these methods has been proposed as a new structural system comprising cold-formed steel (CFS) elements encased in polystyrene aggregate concrete (PAC). In this research, a simplified finite element model has been developed using ANSYS software, where a geometrically and materially nonlinear analysis with imperfections (GMNI) was used to solve the problem of PAC-encased CFS connections and panels subjected to compression. Each model was validated against available test results from literature. The full detailed volume-contact element-based model of concrete was replaced by spring elements perpendicular to the plate’s plane with equivalent properties, where a specific formula was set to define the stiffness of springs. A parametric study was performed to investigate in which range this stiffness has an impact on the ultimate load of the examined members. Additionally, different geometric imperfection amplitudes were implemented to test the real imperfection values. Finally, a failure mode-based equivalent geometrical imperfection amplitude was proposed to anticipate the design resistance of PAC-encased connections and panels.