Axial Compression Performance Test Of GFRP Steel Reinforced Concrete Short Columns

Column members and pier members are important load-bearing members in the building structure,and their durability and load-bearing capacity will have a decisive effect on the service life of the entire structure.In the northwest region,extreme temperature differences between day and night and saline environment will cause the accelerated aging of exposed building materials,especially bridge structures.During service,river erosion,saline environment erosion,external load and other factors will be seriously reduced The service life of the building structure greatly reduces the service life of the structure.In the traditional reinforced concrete pier and column structure,the exposed concrete protective layer is easily corroded by the external environment and the protective layer is peeled off,causing internal steel corro-sion,which affects the service life of the entire structure.Therefore,a new type of urgently needed Com-bine structural columns to make up for the shortcomings of traditional reinforced concrete columns.Based on the Autonomous Region Natural Science Foundation project(2019AAC03004),this article produced a GFRP tube-constrained steel-concrete solid composite short column(Double-Tube Concrete Column,also referred to as DTCC)for testing,through experimental research,numerical simulation and theoretical analysis.In view of the axial pressure performance of the combined column,the main research contents are:(1)Axial compression test of 14 composite short columns was conducted to study their failure modes,load-displacement curves,and analyze the influence of concrete strength,cross-sectional form,steel con-tent,loading mode and other parameters on the bearing capacity of the composite columns.The test results show that:the sandwich concrete basically exhibits 45°oblique shear failure,and the smaller the steel content,the greater the destruction area of the concrete;the load-axial deformation curve of the short column is bilinear,divided into an elastic stage and a strengthening stage;built-in The section steel can significantly improve the ultimate bearing capacity and ultimate deformation capacity of the composite column,but improving the strength of the concrete has limited improvement in the mechanical properties of the composite column.Comparing the hoop strain of the GFRP pipe and the section steel,it is found that the GFRP pipe restrains the concrete later than the section steel The restraining effect of concrete shows a certain hysteresis.(2)The finite element software ABAQUS was used to simulate the axial compression process of the DTCC composite column,and the stress distribution and section steel deformation of the composite col-umn section were analyzed.The simulation results show that the finite element model established in this paper can simulate the axial compression test process better.Based on the established finite element model,the influence of the GFRP tube characteristic parameters on the axial compression bearing capacity of the composite column is studied.It is found that the thickness of the GFRP tube has the largest influence on the composite column bearing capacity,followed by the fiber layup angle,and the material elastic modu-lus has an effect on the combination The effect of column bearing capacity is minimal.(3)The theoretical analysis of the axial compression bearing capacity of the DTCC composite col-umn,based on the test data and the relevant FRP confined concrete research theory,the two-way strain relationship(ie,the expansion curve)of the DTCC composite short column is analyzed,and then the DTCC composite short column is established The axial compression stress-strain analysis model analyzes the stress of GFRP pipe,steel,sandwich concrete and core concrete in the composite column,and finally predicts the load-axial strain curve of the DTCC composite column.The results show that,by considering the two-way stress distribution of the steel tube,this paper distinguishes the sandwich concrete and the core concrete from different constraining effects.The analysis model can predict the load-axial strain curve of the composite column,which can be the theoretical analysis of the DTCC composite short col-umn Provide some reference.