THE STUDY AND APPLICATION Of CONCRETE BOUNDING SURFACE CONSTITUTIVE RELATIONSHIPS TO THE NONLINEAR FINITE ELEMENT ANALYSIS OfCONCRETE FILLED STEEL TUBULAR STRUCTURES

Based on theoretical analyses and the results of tests, the paper studies concrete bounding surface constitutive relationships. The behavior of the material under multi-axial loading is taken into account completely and accurately in the relationships. It is shown that the relationships are simple and effective in nonlinear finite element analysis.