| Reactive powder concrete（RPC）is a new building material with the advantages of high compressive and flexural strength,high toughness and durability.Because RPC has some properties that ordinary concrete does not have,it can meet the requirements of high strength and durability of concrete in long-span buildings and high-rise buildings.On the basis of deep research on steel reinforced concrete structure and RPC,a composite material with high strength,experts and scholars have obtained steel reinforced reactive powder concrete structure,which effectively combines the advantages of high strength and high stiffness of RPC.It has been widely recognized in the field of long-span and super high-rise construction engineering and has a good development prospect.Due to the different composition materials,the working mechanism and failure mode of section steel reactive powder concrete structure are different from that of ordinary section steel concrete structure.With the increasingly extensive application of section steel RPC structure in construction engineering,the research on its mechanical performance is more worthy of attention.Therefore,it is necessary to study the mechanical properties of section steel RPC structure.Based on the above situation,based on the research of domestic and foreign scholars on section steel RPC structure,six section steel RPC columns are designed to carry out experimental research on the bearing performance of specimens under eccentric load.Considering the influence of different eccentricity and different loading angle,including one axial compression comparison specimen,three unidirectional bias specimens（eccentricity of40mm,60mm and 80mm respectively）and two bidirectional bias specimens（eccentricity of80mm and loading angle of 45~0and 90~0 respectively）,the bearing performance and failure mode of each specimen are studied,and the following conclusions are drawn:（1）By comparing the failure phenomena of various specimens,it is found that the failure mode of axial compression specimens is mainly concrete crushing failure,and the failure crack is a vertical crack through the specimen,surrounded by vertical fine cracks,and the internal section steel buckling.For the unidirectional eccentric compression specimens with small eccentricity,the failure mode is mainly concrete crushing failure.When the eccentricity is large,the concrete is pulled off.When this kind of specimen is destroyed,a long and wide failure oblique crack appears,and the oblique crack almost runs through the whole specimen.The failure of bidirectional bias specimens is mainly tensile failure of concrete,tensile transverse cracks appear in the distal axial force side corner,concrete is broken,and wide and long oblique cracks appear in the side of the specimen.The failure of this kind of specimen is mainly inclined cracks and transverse cracks,and there are short and thin vertical cracks near the failure cracks.（2）It can be seen from the load-longitudinal displacement curves under different eccentricity that the ultimate load of unidirectional bias specimens is inversely proportional to the eccentricity,and the ultimate bearing capacity decreases with the increase of eccentricity.The ultimate load of specimens with eccentricities of 40mm,60mm and 80mm is reduced by 37.6%,40.0%and 56.7%,respectively,compared with axial compression specimens.Since the curve changes roughly linearly in the early stage of loading,the slope of the curve at this stage can represent the stiffness of the specimen.By comparison,it is found that the stiffness of the specimen decreases gradually with the increase of eccentricity.In addition,the eccentricity also has a significant effect on the ultimate longitudinal displacement of the specimen under eccentric compression,and the ultimate longitudinal displacement increases with the increase of eccentricity.（3）According to the load-longitudinal displacement curves at different loading angles,when the eccentricity is fixed,the ultimate load decreases with the increase of loading Angle.Compared with the specimens with loading Angle of 0~0,the ultimate load of specimens with loading Angle of 45~0 and 90~0 decreases by 3.2%and 6.9%,respectively.At the initial loading stage,the slope of load-displacement curve of specimens with different loading angles is basically the same,indicating that the loading Angle has little influence on the stiffness of specimens.When the specimens reached the ultimate load,the ultimate longitudinal displacements of specimens with loading angles of 45~0 and 90~0 decreased by 18.37%and43.11%,respectively,compared with those with loading angles of 0~0,indicating that the ultimate longitudinal displacements of specimens decreased with the increase of loading Angle.（4）It can be seen from the load strain relationship curve of RPC at the midspan of the specimen and the load strain relationship curve of section steel that in the initial stage of loading,the strain of reactive powder concrete measuring point and section steel measuring point of each specimen basically maintains a linear increase with the increase of load.As the load continues to increase,the slope of the curve fluctuates slightly,and the measuring points at different positions show different tensile and compressive strain states.When the limit load is exceeded,the concrete reaches the limit strain and is crushed or broken,and the tensile flange and compression flange of the section steel reach the limit strain value and buckling failure occurs.（5）Based on the assumption of plane section and through the calculation of theoretical model,the calculation formula of bearing capacity of unidirectional eccentric compression specimen is derived.Compared with the measured values,the error is small.In addition,the finite element simulation analysis of the test is carried out through the software ABAQUS,which can intuitively show the stress distribution at different positions of the specimen in the model.The ultimate load and load longitudinal displacement curves of the specimens obtained from the simulation results are in good agreement with the test results,which can provide a reference for the study of the bearing performance of steel reactive powder concrete eccentrically loaded columns. |
PDF Full Text Request