Experimental Study And Numerical Analysis On Axial Compression Of Steel Tube Geopolymer Concrete Column

Geopolymer concrete has the characteristics of green,low carbon,environmental protection,steel tube can effectively play a role of constraints of concrete,steel and polymer concrete composite structure can effectively put to combined the advantages of both the polymer concrete and steel,steel tensile properties,with high efficiency to play and efficiency of the polymer concrete compressive properties,the disadvantage of two materials to make up for,The brittleness and strength of geopolymer concrete are improved,so it is more necessary to design the steel tube geopolymer concrete composite members reasonably,so that they can better adapt to the load and environment,and reach the safety,applicability and durability standards of the structure in the service period.Based on experimental analysis,theoretical calculation and finite element numerical simulation,the axial compression performance of steel tube geoparched concrete column is investigated.Completed the following research contents:（1）Axial compression test of steel tube geopolymer concrete column.Designed two empty circular steel tube column and the root of the different types of 24 to polymer concrete filled steel tube column,the parameters of the study include different polymer concrete cube compressive strength,steel tube wall thickness,different length to diameter ratio,one-way under repeated load of artifacts for the axial compression test,explores the stress process of components and failure pattern,The influence of parameter variation on bearing capacity,characteristic displacement,stiffness degradation,ductility,residual deformation and energy dissipation of each component is discussed.（2）On the basis of the limit equilibrium theory,the calculation expression of the bearing capacity of steel tube geopolymer concrete column is established,and the influence of pressure measurement coefficient k₁ on the calculation result is explored.Based on the current domestic and foreign codes,the ultimate bearing capacity of each component is calculated,and the calculation results,test results and optimized expression of the bearing capacity of steel tube geoparmer concrete column are compared and explored.（3）The finite element numerical analysis model of steel tube geopolymer concrete column was established by using ABAQUS software,and the failure state of each component was analyzed.The load-displacement curve obtained by calculation was compared with the test results,which verified the accuracy of the finite element numerical analysis.The main conclusions are as follows:（1）Under repeated axial compression,the peak load of the round steel tube string is small,and the axial deformation increases sharply when the ultimate bearing capacity is exceeded.The strength failure of steel tube geopolymer concrete short column occurred.Obvious lateral flexural deformation occurs in the middle long column of steel tube geopolymer concrete,which is typical elastoplastic failure.The instability failure of long and slender steel tube geopolymer concrete column is not the strength failure.（2）In this experiment,increasing the strength of concrete,increasing the wall thickness of steel tube and decreasing the aspect ratio of specimens can improve the bearing capacity of concrete tube specimens.The lower the strength grade of local polymer concrete,the greater the thickness of steel tube,the smaller the aspect ratio of specimen,and the larger the value corresponding to the residual displacement when unloading to 20k N.The stiffness degradation curve trend of all specimens is roughly the same.The stronger the strength grade of geopolymer concrete is,the larger the wall thickness of steel tube is,the smaller the aspect ratio is,the larger the average compression force of specimens is,and the larger the energy dissipation capacity of specimens is.（3）By using limit equilibrium theory,the calculated result increases with the increase of pressure measurement coefficient k₁.Through optimization analysis,3.07 is recommended.The calculated result is in good agreement with the test result.Referring to the calculation results of current codes at home and abroad,the technical Code for Concrete Filled Steel Tubular Structures（GB50936-2014）is in better agreement with the measured values.（4）According to the finite element numerical analysis,the corresponding stress cloud diagram and load-displacement curve are obtained.Most of the components are in good agreement with the measured results,indicating that the numerical analysis model established can effectively simulate the bearing capacity and deformation performance of the steel tube geopolymer concrete column.