Research On Mechanical Behavior Of Concrete-filled Steel Tube Column-beam Joints Using Special-Shaped Columns And The Joints' Health Monitoring

Concrete-filled steel tube column-beam joints using special-shaped columns are developed from beam-column joint using reinforced concrete special-shaped columns.Its advantages are the use of outer steel tubes to improve the mechanical properties of concrete and the seismic performance of reinforced concrete heterogeneous columns in engineering applications.At the same time,the concrete-filled steel tube column-beam joint with special-shaped columns also have the advantages of short construction period,equal thickness of columns and walls,making the furniture placement more beautiful.Based on the research results and development status of concrete-filled steel tube column,two types of joints are proposed in this paper,namely: T-shaped concrete-filled steel tube column-concrete-filled steel tube beam joint and reinforced T-shaped concrete-filled steel tube columns-concrete-filled steel tube beam joint.The finite element analysis software ABAQUS was used to perform nonlinear finite element analysis on the mechanical properties of the following three joints:T-shaped concrete-filled steel tube column-steel beam joint,T-shaped concrete-filled steel tube column-steel tube concrete beam joint and reinforced T-shaped concrete-filled steel tube column-concrete-filled steel tube beam joint.In addition,joints' health monitoringsystem was introduced.The calculation of the electrical properties of the ideal sensor material,black phosphene,in the sensor subsystem was completed.The research content of the dissertation is divided into the following aspects:1.Using ABAQUS finite element analysis software,based on the test specimen size of the existing T-shaped concrete-filled steel tube column-steel beam joint test,a T-shaped concrete-filled steel tube column-steel beam joint model was established.And its mechanical properties were analyzed under low-cycle load.The calculation results showed that the hysteretic performance of the finite element analysis software was consistent with the joint failure form.This could effectively verify the rationality of the model.Based on this,the two kinds of new joints were designed and calculated.2.The finite element analysis software ABAQUS was used to analyze the mechanical properties of the three joints under unidirectional loading.The results showed that replacing steel beams with concrete-filled steel tube beams and using reinforced slabs could increase the ultimate bearing capacity of joints under unidirectional loads to a certain extent.3.The ABAQUS finite element analysis software was used to calculate the mechanical properties of three kinds of joints under the action of low cyclic load,and the seismic performance indexes of three kinds of joints were obtained.The seismic performance of three kinds of joints were obtained.The results showed that the two kinds of new joints have better energy-consuming performance and higher ultimate bearing capacity than T-shaped concrete-filled steel tube column-steel beam joint,and they showed certain advantages in terms of strength and stiffness degradation.4.The ABAQUS finite element analysis software was used to calculate and analyze the seismic performance of two new types of joints with different coaxial compression ratios,end plate thickness,concrete strength,high-strength bolt specifications,and reinforced slabs thickness of reinforced T-shaped concrete-filled steel tube column-concrete-filled steel tube beam joint.The results showed that changes in end plate thickness and high-strength bolt specifications had a relatively large impact on the seismic performance of the two joints.The changes in axial compression ratio and concrete strength of column and beam had relatively little effect on the seismic performance of the two joints.The changes in reinforced slabs thickness had relatively little effect on the seismic performance of thereinforced T-shaped concrete-filled steel tube column-concrete-filled steel tube beam joint.5.The joints' health monitoring system was analyzed.The CASTEP module in Acclerys Material Studio was used to complete the calculation of electrical properties of the sensor material,black phosphene.According to the calculation results,it could be used as an ideal material for sensors in the joints' health detection system.The sensors on the three kinds of joints were reasonably arranged.