Experimental Study On Mechanical Properties Of RPC Short Column Restrained By Square Steel Tube

Square steel tubular reactive powder concrete is a new combination of forms.Reactive powder concrete has high strength and high brittleness.The constraint of outsourcing steel tubes enables the effective improvement of the elastoplastic properties of the active powder concrete.On the other hand,the active powder concrete filled in the steel tube can prevent the early buckling of the steel tube wall and enhance the stability of the steel tube..Although some experiments have been conducted at home and abroad to strengthen the internal restraint effect,little attention has been given to the additional arrangement of restraint structures inside the steel tube.Little is known about the effect of this measure.In this paper,through axial compression test of 9 square columns of reactive powder concrete columns with different steel fiber contents and spiral stirrup spacings,the steel fiber content and the distance between spiral stirrups are used to study the axial compressive bearing capacity and ductility of the reactive powder concrete short columns.The results show that with the increase of steel fiber content or the decrease of the distance between spiral stirrups,the deformability of square-pipe reactive powder concrete increases,the additional constraint of spiral stirrups on the core concrete and the floc-like net formed by steel fibers Both can play a preset role,and the two methods have different effects on the bearing capacity of the specimen.The configuration of stirrups has a greater effect on the bearing capacity.The stress distributions of specimens with different internal restraints are roughly the same,and they are divided into elastic phase,flexion phase,and failure phase.The final failure modes are basically similar.Using ABAQUS finite element analysis software combined with the content of this experiment to establish a model,determine the constitutive model and element properties ofeach component and according to the actual assembly,simulation analysis,compare the test results to verify the correctness of the model.The simulation analysis found that the configuration of spiral stirrups can change the stress distribution of the internal concrete cross-section,significantly increase the stress level of the core concrete and increase the bearing capacity of the test piece.With the increase of the stirrup spacing,the hoop reinforcement gradually weakens.The deformability of the test piece is then reduced until the steel content is less than a certain degree,and the stirrups basically lose their effect.Simulation analysis of specimens with different wall thickness shows that the wall thickness of the steel tube has a significant effect on the bearing capacity and displacement ductility of the specimen.The larger the wall thickness,the more obvious the effect of the hoop on the internal concrete and the less likely the local buckling occurs.Thus,the higher the bearing capacity,the better the ductility performance.