| Recycled concrete as a new environmental protection building materials has important social benefits and economic benefits,but its mechanical properties are different with ordinary concrete because of its internal aggregate defects.Recycled concrete-filled steel tube by using the restriction of steel tube on the recycled concrete to make up the inadequacy of recycled concrete.But now the research on recycled concrete-filled tube seismic behaviors focused on component level,the overall study of the recycled concrete-filled steel tube frame is relatively rare.In this paper,the basic properties of recycled concrete were studied first,and then the recycled concrete-filled steel tubular frame structure model were built by using the finite element software ABAQUS to study the structural seismic performance.Specific content is as follows:(1)On the basis of the existing test scale specimen KJ-2,recycled concrete-filled steel tubular frame finite element model was established to study its seismic performance which under repeated loading.Then let the results of the finite element compare with experimental results to verify the accuracy of the finite element method.The results showed that the finite element method could well simulate the hysteretic performance,skeleton curve,stiffness degradation,failure pattern and force process of the structure;The plastic hinge of the frame appeared first on the beam end.As the load continue to apply on frame,column yield in its root,and there was no yield surface formed at the joint when the frame destroyed.This meets the design requirements of "strong column weak beam".(2)Under repeated load,separately considered the change of coarse aggregate replacement ratio in the tube,axial compression ratio,grading of recycled concrete in the steel tube,square steel yield strength and the change of the thickness to the seismic performance of recycled concrete-filled steel tube frame.Results showed that hysteresis curve of the recycledconcrete-filled square steel tubular frames were plump and had good energy dissipation ability.The equivalent viscous damping coefficients of different frame were greater than 0.2 when destroyed;With the increase of recycled coarse aggregate replace rate in the tube,the horizontal bearing capacity of recycled concrete-filled steel tube frame model and the initial stiffness decreased,but not very obvious.The ductility coefficient of the frame was changing with the replace rate with no obvious regularity,and the displacement ductility calculation values of different frame model were between 3.35~3.43,therefore,the change should be considered appropriately when designed;Axial compression ratio was higher,the steel tube column foot yielded sooner.At the same time the horizontal bearing capacity and ductility of the frame accelerated degradation.When axial compression ratio was between 0.4~0.5,the seismic performance of the frame could be effectively played;Enhancing the recycled concrete strength grade of column was good for improving the bearing capacity of the frame and the initial stiffness,but had a reverse effect on the ductility and energy dissipation capacity of the frame.Therefore the strength level of the recycled concrete in steel tube should be set properly to consider the actual project;With the increase of square steel tube yield strength,the constraint effect on the internal recycled concrete became obvious,and this made the stiffness and horizontal bearing capacity improve significantly,but the ductility of the frame would be poor,therefore,high yield strength steel should be used in design deliberately;Thickness of column steel tube increase could significantly increase the horizontal bearing capacity and stiffness of the frame,and within a certain range,the ductility of the frame improved with the increase of the thickness of the steel tube,but when the steel tube thickness more than 6mm,the ductility of the frame showed a trend of decrease.So a reasonable thickness of column steel tube should be setting in design. |
PDF Full Text Request