Numerical Modeling of Steel Fiber Reinforced Recycled Concrete Filled Steel Tube Column Under Cyclic Loading

A finite element model (FEM) was created with the aim of analyzing the behavior of steel fiber reinforced recycled concrete (SFRRC)-filled steel tube columns under combined cyclic loading and monotonic axial load. The FEM considered the effect of steel tube confinement on the inner concrete behavior under cyclic loading. The numerical model was described in detail, with a focus on modeling the materials involved (normal concrete, SFRRC, and steel) under cyclic loading. A constitutive concrete model - with and without considering confinement - was based on utilizing a concrete damaged plasticity (CDP) model. The steel tube - concrete core interface was modeled by a surface-to-surface contact. A stress-strain constitutive concrete model, confined by circular steel tubes, was implemented, and validated using experimental results from the literature. The developed FEM considered various parameters: steel tube thickness, volume ratios of steel fibers, besides strengths of both concrete core and the steel tube. The FEM results showed great similarity to the under- cyclic- loading tested columns. The results indicated that the concrete confining pressure must be considered in CDP model. A good correlation between numerical and experimental findings was obvious, including failure modes, and hysteretic curves of load-displacement.