Study On Axial Compression And Seismic Behavior Of Square Steel Tube Spiral Reinforced Self Compacting High-strength Concrete Columns

Square steel tube concrete was favored due to its simple node structure and regular architectural layout.However,compared to circular steel tube concrete,its constraint on the core concrete was weaker.If effective reinforcement can be applied to the square steel tube concrete to compensate for the insufficient constraint of the square steel tube on the concrete,it is of great significance for practical engineering.Existing research has shown that the method of configuring spiral reinforcement inside square steel tube concrete has the best overall performance.However,the spiral steel reinforcement was more complex than ordinary steel reinforcement.During the pouring process,the distance between spiral steel bars and steel tubes was relatively small,which can easily cause the problem of incomplete vibration.Using self compacting concrete for pouring can solve this problem.Based on the background,this thesis proposed a new type of square steel tube spiral reinforced self compacting high-strength concrete column,and used a combination of experiments and finite element simulation to conduct in-depth research on the axial compression and seismic performance of square steel tube spiral reinforced self compacting high-strength concrete columns.The research content and conclusions are as follows:1.This thesis designed and completed axial compression static loading tests on 6 square steel tube spiral reinforced self compacting high-strength concrete columns,observed the failure process of the test,obtained the load displacement curve,and analyzes the influence law of axial compression.The results show that the addition of spiral reinforcement leads to a significant plastic development process in square steel tube spiral reinforced self compacting high-strength concrete columns,and its strength and deformation ability are significantly improved.At the same time,under the same conditions of concrete strength and cross-sectional area,the descending section of high-strength self compacting square steel tube concrete columns with spiral reinforcement was smoother,and the later deformation ability was significantly enhanced.It also provided support for the establishment of finite element models.2.26 models of axially compressed square steel tube spiral reinforced self compacting high-strength concrete columns were established using ABAQUS,and the effects of design variation parameters and expansion parameters on them were analyzed.The results indicate that the thickness of the steel tube has a significant impact on the deformation capacity,but increasing the strength of the steel pipe can only effectively improve its load-bearing capacity.The results show that for the square steel tube high strength concrete specimen with spiral reinforcement,increasing the thickness of the steel tube and increasing the strength of the steel tube can significantly improve its bearing capacity,but the deformation capacity is limited.3.The low cyclic loading test of 7 square steel tube spiral reinforced self-compacting high strength concrete columns were completed.Based on the test data,the influence of shear span ratio,axial compression ratio,spiral stirrup and longitudinal reinforcement spacing on the seismic performance index of the specimens were studied.The strength degradation,stiffness degradation and energy dissipation capacity of the specimen were analyzed.The results indicate that the square steel tube spiral reinforced self compacting high-strength concrete specimens have good seismic performance.Increasing the axial compression ratio appropriately,controlling the shear span ratio within 5,and adding spiral and longitudinal bars have a positive effect on improving the bearing capacity and deformation capacity of square steel tube self compacting concrete columns.4.Established and analyzed the mechanical properties of 22 seismic specimens using ABAQUS,and analyzed the influence of extended parameters such as steel tube thickness and strength,spiral reinforcement diameter and spacing on mechanical indicators.The results of extended parameter analysis show that increasing the thickness of steel tube and selecting larger diameter of spiral reinforcement can improve the ductility and shear capacity of the specimen,while the strength of steel tube only affects the improvement of shear capacity.This paper has received funding from the Guangxi Eight Guangxi Scholars Special Research Fund Project(2019 [79]),the Central Guiding Local Science and Technology Development Fund Project(Guike ZY21195010),the Guangxi Science and Technology Base and Talent Special Project(Guike AD21075031),and the Guangxi Key R&D Plan Project(Guike AB21220012).