Study On Short Age Mechanical Properties Of Self Compacting Concrete And Axial Compression Behavior Of Steel Reinforced Self Compacting Concrete Columns

Self compacting concrete(SCC)has been widely used in super high-rise buildings.Since the mechanical properties of self compacting concrete at different ages directly affect the engineering quality and service state in the later stage,it is necessary to study the time-varying law of mechanical properties of self compacting concrete in a short period of time to reveal its internal essence,and provide important support and basic data for the establishment of mechanical analysis theory in the construction stage of super high-rise buildings.Steel reinforced concrete column structure is the foundation bearing structure in high-rise buildings,in which axial compression is the most basic stress form of steel self compacting concrete column.The previous studies are focused on steel reinforced concrete columns,and there is little research on the performance of steel reinforced self compacting concrete columns under axial compression,and a set of systematic theory has not yet been formed.Based on this,the mechanical properties of self compacting concrete(SCC)blocks and steel reinforced self compacting concrete(SRC)columns under axial compression are studied by means of test and finite element analysis.On this basis,the constitutive equation of self compacting concrete and the calculation method of axial compression bearing capacity of SRC columns are proposed1.The axial compression,elastic modulus and splitting tensile tests of 48 self compacting concrete cylinder specimens and 12 self compacting concrete cube specimens under short age were completed.The compressive stress-strain curve of self compacting concrete was obtained by observing the failure process and shape of the specimen.The calculation formula of time-varying and relationship of mechanical properties indexes and uniaxial compression constitutive equation were proposed.The results show that the axial compressive strength,splitting tensile strength and axial compression stiffness of self compacting concrete increase with age,while the relative toughness decreases.The modified constitutive equation of uniaxial compression can accurately describe the deformation characteristics of self compacting concrete.2.The axial compression tests of 5 steel reinforced self compacting concrete columns are completed.The failure process and failure mode of the specimens were observed.The load longitudinal displacement curve,the load strain curve of steel and self compacting concrete and the related mechanical property index parameters were obtained.The results show that: with the increase of stirrup spacing,the ultimate bearing capacity,ductility and energy consumption of the specimens decrease,and the influence on the initial stiffness is small;the slenderness ratio has a significant impact on the axial compression stiffness of the specimens.3.The finite element model is established to simulate the axial compression process of steel reinforced self compacting concrete column.The results of failure mode,load displacement curve and ultimate bearing capacity of the simulated specimens are compared with the test results,and the simulated values are in good agreement with the experimental values.Furthermore,the influence of steel type and size,stirrup reinforcement ratio,longitudinal reinforcement ratio,slenderness ratio and concrete strength on the ultimate bearing capacity and load displacement curve of steel reinforced self compacting concrete columns are analyzed.Through the analysis of the internal force contribution of each part of the specimen,the corresponding configuration parameters of steel and stirrup longitudinal reinforcement are obtained.4.On the basis of experimental research and finite element analysis,the calculation formula of axial compression bearing capacity of steel reinforced self compacting concrete column is established,and compared with the test data in this paper and the relevant literature test data,the test and related literature data verify that the bearing capacity calculation formula proposed in this paper has good calculation accuracy and small dispersion.