Research On Axial Compression Performance And Design Method Of Steel-tube And Desert Sand Lightweight Aggregate Concrete Composite Short Columns

Replacing part of river sand with desert sand and fly ash cenosphere to produce lightweight aggregate concrete can effectively reduce the supply demand of river sand,and can also reuse waste to protect the environment.At the same time,the replacement of river sand with fly ash cenosphere can reduce the increase of concrete bulk density caused by the replacement of river sand with desert sand,and a small amount of polymer is added to improve the bonding performance between aggregates.However,the desert sand lightweight aggregate concrete has great brittleness and poor ductility.Inspired by the composite members of concrete filled steel tubes,the desert sand lightweight aggregate concrete and steel tubes are combined to form the composite members of desert sand lightweight aggregate concrete filled steel tubes.Its strength and ductility can be significantly improved.Because the mechanical properties of desert sand and fly ash cenosphere mixed to replace part of river sand are not clear for the time being,the basic mechanical properties of lightweight aggregate concrete prepared by desert sand,fly ash cenosphere and polymer are studied.ABAQUS finite element analysis software is employed to propose the stress strain relationship of desert sand lightweight aggregate concrete,constrained by steel pipes,based on the mechanical property test.Subsequently,short column axial compression test and finite element analysis are conducted,with the pertinent parameters being analyzed.Finally,the bearing capacity calculation formula is proposed in relation to the applicable specifications.The main work is as follows:(1)The single factor test method was employed to investigate the effect of desert sand replacement rate,fly ash cenosphere replacement rate,and polymer lotion content on the fundamental mechanical characteristics of desert sand lightweight aggregate concrete.Finally,the optimal mixing amount of desert sand,fly ash cenosphere and polymer lotion was obtained.The effect of desert sand and fly ash cenosphere on the microstructure of concrete is analyzed,and three groups of mix proportion are selected from the mix proportion test.The axial compression test of desert sand-filled steel tubular lightweight aggregate concrete short columns is achieved by the concrete strength reaching C25,C30,and lightweight aggregate concrete respectively(2)The stress-strain curve of desert sand lightweight aggregate concrete is determined by fitting the existing concrete stress-strain curve,while the cylinder axial compressive strength of C25 and C30 concrete is investigated.ABAQUS finite element analysis software simulates the stress-strain curve relationship of desert sand lightweight aggregate concrete,constrained by steel pipe,and then compares it to the existing constrained concrete model.The modified stress-strain curve relationship of desert sand lightweight aggregate concrete is then established.(3)Axial compression tests were conducted on five steel tube desert sand lightweight aggregate concrete short columns,the failure patterns and results of which were then analyzed.The finite element model of desert sand lightweight aggregate concrete short column is established,based on the stress-strain curve of desert sand ceramsite concrete confined by steel tube,and the axial compression test process of desert sand lightweight aggregate concrete short column is simulated.Verification of the model’s precision is accomplished through the examination.The axial compression performance of members is investigated in terms of the impact of concrete strength grade,yield strength of steel pipes,wall thickness and length-diameter ratio.Revising the bearing capacity calculation formula of desert sand lightweight aggregate concrete filled steel tubular short columns,the test results were compared between domestic and foreign specifications for calculating the bearing capacity of concrete filled steel tubulars.Subsequently,design suggestions for desert sand lightweight aggregate concrete filled steel tubular short columns were provided...