Experimental Study On Constitutive Relation Of Rectangle Steel Tube Filled With Demolished Concrete Blocks And Its Application

The rapid development of urbanization in China has brought the rapid development of the construction industry,but also produced a large number of construction waste.If the application of recycled concrete in the building,it can effectively reduce the pressure on resources and the environment.Recycled concrete filled steel tube structure can not only play their respective advantages of the steel tube and concrete,also consumes part of waste concrete,to achieve concrete recycling.However,there are few researches on the structure of recycled concrete filled rectangular steel tube,especially the constitutive model of this kind of structure.Therefore,based on the existing research,this paper studies the constitutive relation of rectangular steel tube filled with recycle concrete blocks.The constitutive relation model of concrete filled square steel tube is adopted in the rectangular steel tube filled with recycle concrete blocks at home and abroad,and the effect of the height to width ratio in the rectangular section on the constitutive relation is not considered.Therefore,this paper takes the section height to width ratio of the main control parameters,considering the effects of steel ratio,mixing ratio,strength of steel and concrete and other factors,the design of the 24 rectangular steel tube recycled mixed concrete short column specimens.Study on constitutive relation of recycled concrete filled rectangular steel tube by axial compression short column test.The experimental results show that:(1)the height to width ratio of the cross section has an effect on the mechanical properties of the rectangular steel tube filled with recycle concrete blocks.With the increase of the ratio,the increasing coefficient of the bearing capacity decreases,and the constitutive relation;(2)with the increase of strength of steel and concrete,recycled concrete filled rectangular steel tube short column axial compression bearing capacity is increased.Mixing ratio on bearing capacity is limited;(3)with the increase of steel strength,steel ratio,concrete strength,section height to width ratio,mixing ratio,the ductility of recycled concrete filled rectangular steel tube short columns is increased.Comparative analysis of the constitutive relationship model of steel and coreconcrete at home and abroad,combined with the test data,considering the influence of height to width ratio ratio,put forward the suitable constitutive relation in rectangular steel tube recycled mix concrete.Based on the constitutive relation of the material,the finite element method is applied to the numerical analysis of axial compression short column specimens,and the results are compared with the experimental results and the existing constitutive models.The results show that the simulation results are in good agreement with the experimental results,and the rationality of the constitutive relation is verified.Compare ACI 318-05-2005,AIJ-2008,BS5400-2005,CECS159:2004,DBJ13-51-2003,EC4-2004,GB50936-2014 for recycled concrete filled rectangular steel tube axial compression bearing capacity calculation formula,the calculation results are be safe,it is recommended to use DBJ to calculate the ultimate bearing capacity of Recycled concrete filled rectangular steel tube.On the basis of the research of this subject,according to the test results,the calculation formula of axial compression bearing capacity of rectangular steel with tube recycle concrete blocks is put forward.