Fracture prediction of welded steel connections using traditional fracture mechanics and calibrated micromechanics based models |
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Authors: | Yuanqing Wang Hui Zhou Yongjiu Shi Jun Xiong |
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Affiliation: | (1) Swiss Federal Institute of Technology, 1015 Lausanne, Switzerland.;(2) Poulter Laboratory, SRI International, 333 Ravenswood Avenue, Menlo Park, CA, 94025-3493, U.S.A |
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Abstract: | Fracture resistance is of primary concern in the seismic design of beam-to-column connections in steel moment resisting frames
(SMRFs). Micromechanics based fracture models such as the void growth model (VGM) and the stress modified critical strain
(SMCS) model provide alternative approaches for ductile fracture prediction by relating micro-mechanisms of void nucleation,
growth and coalescence to macroscopic stresses and strains. In this study, the VGM and SMCS models were calibrated for Q345
structural steel and the corresponding weld, through smooth notched tensile (SNT) tests and complementary continuum finite
element models (FEMs). A series of seven local connections representing beam-to-column connections in SMRFs were tested under
monotonic tensile loading and the specimen elongations at fracture critical point were obtained. The traditional J-integral
based fracture mechanics and micromechanics based fracture models (VGM and SMCS) were applied to predict fracture in each
tested local connection through refined three-dimensional FEM. Comparisons between these numerical approaches and experimental
observations in prediction of fracture critical displacement, indicated that the VGM and SMCS models were able to predict
fracture of welded connection with good accuracy, while the J-integral based approach resulted in quite conservative fracture
prediction. This paper has bridged the gap between small-scale material tests and large-scale structural experiments in fracture
evaluations. |
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