Eccentric Tension And Compression Hysteretic Behavior Research Of Circle Tubular Steel Members Based On Micromechanical Fracture Prediction Theory

Circular steel tube is widely used in large-span spatial structures. Under strong earthquakes, the stress state of large-span spatial structure boundary components is complex, generally existing axial force, shear force and bending moment of internal force and larger amplitude variation. Therefore, the case that different degrees of damage or even fracture of circular steel tube components happens is frequently reported. But lack of a systematic study of hysteresis behavior under complicated stress state for the circular steel tube components currently, based on this, this paper studies hysteresis behavior of circular steel tube components under eccentric tension and compression loading way considering the coordinated variation of axial force and bending moment combined with testing and large-scale parametric analysis, and based on CVGM micromechanical fracture prediction theory. The main work is as follows:(1) The smooth and notched strip specimens which were extracted from Q235B hot rolled seamless circular steel tube were designed and processed, and the uniaxial tension test and ultra-low cyclic loading test was carried out. On the basis of Guo paper’s recognition of monotonic loading VGM toughness parameter, parameter of micromechanical fracture models CVGM were calibrated through ultra-low cyclic loading test results. The fracture predictions of notched specimens under cyclic loading matched well with experiment results.(2) The experimental researches on the hysteretic behavior of the seven circular steel tubular components full-scale models under the action of eccentric cyclic tension and compression load have been completed. The effects of the slenderness ratio, eccentricity and initial axis pressure ratio on the hysteretic behavior of the test specimens were ananyzed from the experimental phenomenon, hysteretic curve, skeleton curves, energy dissipation, ductile fracture and fracture circle number,(3)Finite element model of Circular steel tube specimen was established by finite element analysis software ABAQUS. The effect of initial imperfection, material nonlinearity and geometric nonlinearity of the finite element model based on micromechanical fracture prediction theory has been considered. The results show that the finite element model can accurately reflect the nonlinear properties of circle tubular steel members. The CVGM model was used to predict ultra-low cycle fatigue fracture. The validity of the numerical analysis method in this paper was verified.(4) The hysteretic behavior of circular steel tubular members under the action of eccentric cyclic tension and compression load has been analyzed largely. Through the e hysteretic curve, skeleton curves, energy dissipation, ductile fracture and fracture circle number, we discussed the effects of the slenderness ratio, eccentricity and initial axis pressure ratio on the hysteretic behavior of the circular steel tubular members.