Experimental Study On The Axial Compression Behavior Of Short Steel Tube Columns Filled With High-strength Manufactured Sand Concrete

The replacement of natural river sand with machined sand for the preparation of high-strength concrete will,to a certain extent,alleviate the conflict between the lack of natural river sand resources and the increasing demand for construction,and effectively solve the environmental problems caused by over-extraction of natural sand.High-strength machined sand concrete has the advantage of high strength,but its brittleness is also very large,so it is more difficult to directly apply it to engineering practice.The steel is poured into the steel pipe,the brittleness of the steel pipe is improved by the restraint effect of the steel pipe,and the material properties of both are fully exerted.Therefore,the composite component has the advantages of high bearing capacity,strong deformability,and good ductility.The axial compression performance reflects the basic mechanical properties of the composite member of steel tube concrete.The research on the axial compression performance of ordinary concrete structural steel tubes has been carried out quite well.However,there has been no report on the study of high-strength concrete sand-filled concrete.In this paper,54 short column members of high-strength manufactured sand concrete filled steel tube were designed and subjected to axial compression experiments.The influences of various parameters on the axial compression performance of high strength sand-concrete reinforced concrete short columns were studied by taking the diameter-thickness ratio of steel pipe,the shape of sand as raw material,the strength of sand-reinforced concrete and the sand content of mechanism sand as the inspection parameters.The stress-strain curves of high-strength sand-concrete-reinforced concrete confined by steel tube are studied,the constitutive model is proposed,and the accuracy of the constitutive model is verified.(1)In the axial compression test of high strength sand-concrete concrete columns for steel tubes,the bearing capacity,displacement,and steel tube strain in the whole test process was measured.Observe the damage rules of the test piece in the test.In the axial compression test,the steel pipe high strength concrete short column mainly exhibits two failure modes of shear type and waist drum type;and the analysis shows that the longitudinal load-deformation curve of the test piece is mainly divided into elasticity,Elastoplasticity,descending segment,and strengthening these four stages.(2)The failure modes of the high strength concrete-strengthened sand-concrete short columns in axial compression tests,the relationship between the axial force of specimens and the longitudinal compression deformation,the longitudinal strain changes of the steel tubes and the lateral deformation characteristics of the specimens were analyzed,and the ratio of diameter to thickness and the core mechanism sand concrete were found.The effect of strength on the deformation characteristics and failure modes of test specimens with high mechanical strength sand-in-concrete has a great impact;on the basis of the analysis,the causes of the two types of failure modes of waist-drum type and shear-type of high-strength machine-made sand-concrete are analyzed,and the high-strength pipe-sand concrete of steel tubes is further analyzed.Principle of force under axial compression.(3)The influence of the factors such as the original morphology of machined sand(limestone,pebbles),strength of machined sand concrete(C60,C80,C100),mechanical sand content(3%,5%,7%),and ratio of pipe thickness to thickness(D/ t(28)28?32.5 38?)were studied for the ultimate bearing of high-strength mechanism concrete of the steel pipe.(4)Based on the axial compression test,the formula for calculating the bearing capacity of the high strength concrete sand-concrete short columns was deduced,and the formulae were deduced with Zhong Shantong's formula,Han Linhai's formula,Cai Shaohuai formula,China's specification CECS28-90,European norm EC4-1994 formula and the United States.The steel structure association AISC360-2005 formula is compared.(5)Based on the test,the stress-strain curve of the core high-strength mechanism sand concrete is obtained,and statistical regression is performed on the ascending and descending sections of the curve.The stress-strain constitutive relation of the sand concrete concrete is constrained,and on this basis,the high-strength sand concrete is restrained.The stress-strain curve and the simulated curve are comparable to verify the rationality of the relation.