Elasto-plastic Natural Element Method (NEM) and its application in numerical experiments of concrete filled steel tubular(CFST) columns

The Natural Element Method (NEM) is a numerical method, which constructs the interpolation based on the Voronoi tesselation of a set of nodes, does not rely on the grid, owns the advantages of meshless method. In NEM, the shape functions meet the properties of KroneckerDelat function, which makes it impose the boundary conditions easily. Based on the advantages of NEM, the elasto-plastic NEM is investigated. Finally, the elasto-plastic NEM is applied for the numerical experiments of concrete filled steel tubular (CFST) columns. The results of concrete column verify the correctness and rationality of the elasto-plastic NEM. Firstly, the CFST columns composit of C30 concrete with different Poisson's ratio had been researched, the results show that the plasticity, toughness and strength of concrete in CFST have been enhanced, and with the increases of Poisson's ratio, the enhancement of plasticity, toughness and strength of concrete increase. Another experiments are for the CFST columns composit of different grades concrete, the results show that the plasticity, toughness and strength of concrete in CFST have been enhanced, but the enhancement does not with the concrete grades.