Experimental Study About Mechanical Properties Of Steel Tube-reinforced Recycled Concrete Composite Column Under Eccentric Compression

The development of modern construction industry leads to not only a large amount of consumption of natural sand and stone resources,and the energy consumption due to the mining and transportation,but also the destruction of the ecological environment due to the mining of natural sand and stone.The disposal of huge amount of construction waste from the old building demolition needs a lot of money and the damage to the environment could not be eliminate in a short period of time.The defect of recycled concrete in comparison with the ordinary concrete limits its application.The price of recycled concrete has not advantage when compared with ordinary concrete due to the imperfect production and use chain of recycled concrete,thus further limits the application of recycled concrete.Therefore,expand the scope of the application of recycled concrete become a big problem to be solved at the moment.Steel tube-reinforced recycled concrete composite column is a product that conforms to the trend.The application of recycled concrete in the column type,not only save energy and protect the environment,but also give full play to the advantages of steel and recycled concrete,making it not only has high bearing capacity,large stiffness and good seismic performance of concrete filled steel tube,but also has more excellent fire and corrosion resistant properties than that of concrete filled steel tube.Through the static test of steel tube-reinforced recycled concrete composite columns under eccentric compression,to study its mechanical properties.The main parameters of this test are replacement ratio of recycled coarse aggregate,steel ratio,slenderness ratio and eccentricity,etc.The main conclusions are shown as follows:(1)The main factors that influencing the mechanical properties of steel tube-reinforced recycled concrete composite columns under eccentric compression are eccentricity,steel ratio and slenderness ratio,while the replacement ratio of recycled coarse aggregate has no significant effect.(2)The strain change of all parts of the composite column in different damage stage has a close relationship with parameters.Overall,each part is collaborative working in the linear elastic stage,and the collaborative ability of small eccentricity specimens is relatively better.The specimens conform to the sine half-wave hypothesis.Under the condition of large eccentricity,the influence of recycled coarse aggregate replacement ratio to ductility coefficient and energy dissipation capacity of composite column is bigger than that of small eccentricity.(3)The calculation formula of this column which under eccentric compression adopts superposition method,through the correction to related parameters of reinforced concrete and concrete filled steel tubular respectively,to consider the influence of eccentricity,steel ratio and slenderness ratio to bearing capacity and the strengthening effect between reinforced concrete and concrete filled steel tube.(4)Compared with other scholars' superposition method,a preliminary judgment method to determine the value range of compressive zone height x was given;The correction coefficient of bearing capacity which taking the diameter of steel tube as limit was given;The calculation formula of this column which under eccentric compression and the condition that the value of neutral axis is larger than the cross section height is given in detail.It shows that,the calculation results coincide well with the experimental results.