Mechanical Behavior Of Concrete Filled Corrugated Steel Tube Under Pure Bending

Concrete filled steel tube members(CFST)exhibit excellent mechanical properties due to the superior composite action between steel tube and concrete.At the same time,steel tube can also be used as a template for pouring concrete during the construction phase.Nowadays,CFST has been widely recognized by scholars all over the world and has been widely used in various of engineering practice.However,when reinforced concrete beams are used,the joints between the concrete filled steel tube column and the reinforced concrete beam are complicated.Therefore,tubed reinforced concrete(TRC)have emerged as the times require.The TRC menber is to break the steel pipe in the core area of the beam and column joint on the basis of the concrete filled steel tube,to make sure the outer steel pipe does not directly bear the vertical load,but mainly plays the role of restraining the core concrete.In recent years,scholars all over the world have carried out a lot of research on its mechanical properties and TRC member has been applied in practical engineering.The concrete filled corrugated steel tube(CFCST)which proposed by the Metal and Composite Structure Research Center of Harbin Institute of Technology in recent years has similar force features to TRC member.The presence of corrugations significantly improves the local stability of the steel tube.In addition,the external galvanized corrugated steel tube has excellent corrosion resistance,which can enhance the durability of the components and reduce the maintenance.It can be foreseen that CFCST member has broad application prospects.In this paper,the flexural behavior of concrete filled corrugated steel tube members is studied experimentally and theoretically.The main contents are as follows:1.The pure bending test of three CFCST specimens and three TRC contrast specimens was completed,and the moment-curvature curve and stress-strain distribution curve were obtained through experiments.By analyzing the flexural mechanical properties of CFCST and TRC,the definition indexes of bending capacity and bending stiffness for CFCST are proposed.2.The finite element model of CFCST under pure bending is established by using the Abaqus finite element software.The established Abaqus finite element analysis model can consider the influence of corrugated folds of corrugated steel pipe(CSP).By selecting appropriate stress-strain relationship,setting proper contact and constraint to make sure the model has good convergence.Then the Abaqus finite element is reasonably corrected based on the test results to obtain the accurate finite element model.Finally use the model to analyse the non-uniform constraint mechanism of CFCST.3.The calculation method of the flexural capacity and flexural rigidity of similar members in different countries is coMPared and analyzed.The fiber model method for CFCST was developed by using MATLAB software,and it was verified by experiment.Based on the fiber model,parameter analysis was carried out on the flexural capacity and flexural rigidity of CFCST.The parameters include the axial compressive strength of concrete,the yield strength of longitudinal reinforced bars,the steel ratio of reinforced bars,the equivalent restraint stress provided by corrugated steel pipe,the Arrangement of reinforced bars,etc.The calculation formulas of flexural capacity and flexural rigidity of corrugated steel tube members are obtained based on theoretical derivation and regression fitting.It has been verified that the formula has good prediction accuracy.