Simulation Study On Compressive Behavior Of Concrete Columns With Core Enclosed By Ultra-High Performance Concrete

Ultra-high performance concrete,as a kind of fiber-reinforced cement-based composite material,is prepared by dense particle accumulation method,and it has far more mechanical properties and deformation capacity than normal strength concrete.It has compact internal structure,low porosity and ultra-high impermeability,which can greatly improve the durability of the structure and reduce the maintenance cost during the service period of the structure.Compared with the traditional concrete structure,the service performance of the structure can be effectively improved and its service life can be prolonged by using ultra-high performance concrete.However,considering that the high cost and preparation process standard of ultrahigh performance concrete,in order to comprehensively utilize the advantages of ultra-high performance concrete and normal strength concrete,this thesis proposes a kind of concrete column with core enclosed by ultra-high performance concrete,whose core area is normal strength concrete.Through a certain thickness of ultra-high performance concrete around the core area,it can not only effectively improve the durability of components,but also significantly enhance the mechanical properties and deformation ability of the structure.With the combination of numerical simulation and theoretical analysis methods,this thesis studies the mechanical state and compression performance of concrete column with core enclosed by ultrahigh performance concrete under axial compression and eccentric compression,and then put forward the design suggestions of ultra-high performance concrete columns around the core area.The main research contents and conclusions of this thesis are as follows:(1)The axial compression performance of concrete column with core enclosed by ultrahigh performance concrete is simulated.A total of 28 simulation specimens were set up to study the effects of different peripheral ultra-high performance concrete thickness,stirrup configuration,longitudinal reinforcement configuration and normal strength concrete strength in the core area on the axial compression performance of the specimens.The simulation results show that the thickness of ultra-high performance concrete layer has a significant effect on the axial compression performance of specimens.When the thickness of ultra-high performance concrete layer increases,the axial compression bearing capacity and the growth rate of bearing capacity will increase.Other structural parameters have little influence on the bearing capacity.Ultra-high performance concrete and normal strength concrete in the core area can work together,the relative slip between the two materials can be ignored,and the restraint effect of ultra-high performance concrete on normal strength concrete in the core area is weak.(2)The eccentric compression behavior of concrete column with core enclosed by ultrahigh performance concrete is simulated.A total of 36 simulation specimens are set up to study the effects of different eccentricity,peripheral ultra-high performance concrete thickness,stirrup configuration,longitudinal reinforcement configuration and normal strength concrete strength in the core area on the eccentric compression performance of the specimens,analyze the simulation results and summarize the influence laws of various parameters.The simulation results show that the eccentricity and the thickness of ultra-high performance concrete layer have the most significant influence,and there is a certain coupling effect between the two parameters,while other parameters have a weak influence on the eccentric compression performance of ultra-high performance concrete columns around the core area.The eccentric compression bearing capacity of concrete column with core enclosed by ultra-high performance concrete will decrease with the increase of eccentricity and increase with the increase of the thickness of ultra-high performance concrete layer.At the same time,increasing the eccentricity and the thickness of ultra-high performance concrete layer will weaken the increase of eccentric compression bearing capacity.There is no obvious relative slip between ultra-high performance concrete and normal strength concrete in the core area,and the interaction between them is weak.(3)The calculation formula of compressive bearing capacity of concrete column with core enclosed by ultra-high performance concrete is proposed.Based on the idea of strength superposition,combined with the calculation idea of compressive bearing capacity adopted in code for design of concrete structures(GB 50010-2010),different bearing capacity calculation formulas are proposed for the two compression states(axial compression state and eccentric compression state)of concrete column with core enclosed by ultra-high performance concrete.For the axial compression state,compared with the standard bearing capacity calculation formula,the calculated bearing capacity obtained by the axial compression bearing capacity calculation formula proposed in this thesis is more consistent with the simulated bearing capacity;For the eccentric compression state,the calculation formula of eccentric compression bearing capacity proposed in this thesis can also better reflect the simulated bearing capacity.The applicability and accuracy of the two compression bearing capacity calculation formulas have been effectively compared and verified.