Experimental Study On The Flexural And Shear Resistance Performance Of Steel Tube Beams Filled Self-compacting Mixed Brick Recycled Aggregate Concrete

In recent years,the environmental problems caused by the secondary pollution of construction waste and excessive exploitation of resources are increasingly serious.Green concrete is prepared by using the aggregates from crushing waste brick and waste concrete,which can effectively solve a large number of construction waste and reduce the ecological problems caused by over exploitation of natural sand and stone.In this paper,the mix proportion of self compacting recycled concrete with mixed brick aggregate is designed.The mechanical properties of self compacting recycled concrete with mixed brick aggregate and the bending shear properties of mixed brick aggregate self-compacting recycled concrete filled steel tube beams are studied through experiments.The finite element software ABAQUS is used to verify the results.It is expected to provide theoretical and experimental basis for the popularization and application of this kind of aggregate and composite structure.The main contents and conclusions are as follows:Based on 18 mixed brick aggregate self-compacting recycled concrete filled steel tube beams,the effects on their shear capacity of different shear span ratio,aggregate type,wall thickness of steel tube and whether there are end plates at both ends of the specimens are studied.Through comparative analysis of the failure mode,local stress-strain,load displacement relationship and ultimate shear bearing capacity,the following conclusions are drawn: When the shear span ratio λ is 0.1 and 0.3,shear failure occurs;when the shear span ratio λ is 0.5,bending shear failure occurs;when the shear span ratio λ is 0.85,bending failure occurs.The shear capacity decreases with the increase of shear span ratio.The shear capacity of the members with brick aggregate is equivalent to that of the members with mixed brick aggregate.The thicker the steel pipe wall is,the larger the shear capacity of the specimen is.The shear capacity of concrete filled steel tube is significantly higher than that of the empty steel pipe.The slip between concrete and steel tube is measured by the specimen without end plate,and it is found that the slip is positively correlated with the shear span ratio.According to the existing domestic literature,the shear capacity of mixed brick aggregate self-compacting recycled concrete filled steel tube beams with different calculation methods is compared.Among them,the design value of GB50936-2014 is the closest to the test result,and the safety is low.Based on the experimental study of two mixed brick aggregate self-compacting recycled concrete filled steel tube members and one brick aggregate self-compacting recycled concrete filled steel tube member,the variation of deflection and surface strain value of steel tube,failure characteristics and ultimate ultimate bending moment are analyzed,and the influence of aggregate type and wall thickness of steel tube on them is obtained.The test results show that the change of aggregate type causes the change of core concrete strength,but the flexural capacity is not affected by it.The increase of the wall thickness of the steel tube has an obvious effect on the bending capacity and the bending rigidity.In this paper,six literatures at home and abroad are summarized to compare the flexural capacity of mixed brick aggregate self-compacting recycled concrete filled steel tube beams.Among them,the theoretical calculation value given by BS 5400 is the closest to the test result.The finite element software is used to simulate the bending and shear test of mixed brick aggregate self-compacting recycled concrete filled steel tube beams.Through the comparison test and the simulation of the failure mode and the force(bending moment)-displacement curve,it is found that the two results are in good agreement,and then analysis of the causes of errors.