Study On Fracture Prediction Of Building Steel Joints Using Micromechanical GTN Model

ABSTRACT:Steel joints’failure is often the main cause of steel structure accident. Studying steel and joints from the perspective of microcosmic is more scientific and reasonable. However, there are very few domestic researches in China. Therefore, this paper will apply the GTN damage mode, which is widely used at home and aboard, to the parameters acquisition of steel commonly used in construction industry and joints.First of all, smooth and notched round bar specimens are designed and manufactured from material of Q235B hot-rolled seamless pipe, welded pipe’s base metal, hot-affected zone, weld and cast steel pedestal. Then the specimens are tested under uniaxial tension and low cycle loading respectively. The basic mechanical parameters of each kind of steel are obtained from the uniaxial tensile tests, and hysteretic curves and skeleton curves are obtained from the low cyclic tests. Then mechanical properties of each kinds of steel are compared. The uniaxial tensile specimens’fractures are analyzed by SEM and the fracture failure mode of each kind of steel are compared. Taking the Q235B hot-rolled seamless steel pipe’s base metal as an example, different notch radii specimens’ fractures are compared. The SEM photos’ results are in line with the metal microvoid coalescence theory.Then notched specimens’uniaxial tensile tests of each kind of steel are simulated and analyzed using GTN model, and five kinds of steel’s GTN parameters are obtained and compared. It is found that GTN model can accurately predict the fracture of five kinds of steel. Two sets of q parameters in GTN model are compared and they can both predict the fractures of notched specimens’tensile test well.Finally, K-joint and cross plate welded joint are simulated based on the GTN parameters obtained above. The effect of GTN damage parameters, f0、fn、fF、q1and q2on the fracture prediction of steel joints are researched. The good results showed that studying the practical engineering using GTN damage model is feasible and superior.