Study Of The Mechanical Properties Of Dual-chamber Reinforced Concrete Core Walls With Mixed Concealed Bracings

The core tube structure of reinforced concrete is widely used in practical engineering due to its outstanding mechanical behavior, such as strong lateral stiffness, high bearing capacity, good ductility, good space and overall performance, which has become the main bearing components in high-rise buildings. Reinforce concrete core walls with mixed concealed bracings is one kind of new improved form of ordinary reinforced concrete. Through adding mixed concealed bracings into RC core, the initial stiffness, bearing capacity, ductility and deformability of RC core have been greatly improved. However, the research and application is still not mature currently. Further study is not only the need of analysis theory development of high-rise buildings, but also the key to solving the practical engineering problems. Currently theoretical and experimental research in academia is mainly aimed at single-chamber core tube, paying more less attention to the dual-chamber core tube which has been widely used in practical engineering. According to this situation, the major research of this thesis is the mechanical property of the dual-chamber core tube. An important mechanical behavior of the core tube structure of reinforced concrete is that it has the obvious shear lag effect, which decreases the whole structure function, the material cannot fully play the role, a nd the section design is not accurate. Strengthening study on the shear lag effect of the core tube structure is to fully understand the working performance of the core tube and the inevitable requirement of structural design optimization. Based on the background that computer technology and finite element technology has been developed rapidly in recent decades, this thesis applies ABAQUS software for finite parameter analysis and element simulation of the dual-chamber core tube.The thesis concentrates on the dual-chamber reinforce concrete core walls with mixed concealed bracings, the dual-chamber reinforced concrete core tube with X rebar concealed bracing and the ordinary dual-chamber reinforced concrete core tube, and stresses on the analysis of the distribution and of the shear lag effect, the development of the shear lag effect and influence factors of the shear lag effect. The thesis has completed the following research:Firstly, this thesis uses the finite element analysis software ABAQUS to simulate model of reinforce concrete core tube in reference literature by finite element simulation. The thesis also analyses and discusses the constitutive relation of concrete, parameter settings, material property, rebar in the modeling process, the selection of element type and mesh and mesh generation. By comparing the calculation results with test results and the causes of the error analysis, it turns o ut that using ABAQUS software to simulate model can well simulate the mechanical properties of reinforced concrete core tube under monotonic loading, and the dual-chamber core tube model is also on the basis of reference literature.Secondly, this thesis utilizes numerical stimulation method to reinforced concrete core tube with different structures and loading ways, which researches on shear-lag effect of the core tube make use of the results of the longitudinal strain from the bottom flange section of the calculation model. In order to quantify the shear lag effect of the core tube, the "shear lag value" defined in this thesis is the ratio of maximum longitudinal strain and the average longitudinal strain of flange section. Also the "shear lag value" could reflex the non-uniformity of longitudinal strain of the core barrel flange. The thesis focuses on the manifestation, the distribution characteristics and the change rule of the shear lag effect of the reinforced concrete core tube under the horizontal load force. This thesis also discuss the problem that what impact does the type of concealed bracing, axial compression ratio, the couple beam span-depth ratio, the type and amount of the mixed concealed bracings in the wall and the existence of the coupling beam structural steel have on the shear lag effect.Thirdly, this thesis compared the seismic behavior of single-chamber core tube and the dual-chamber core tube with different types of concealed bracings and loading method. In order to discuss the problem that what impacts does the type of concealed bracing, axial compression ratio, axial compression ratio, the couple beam span-depth ratio, the type and amount of the mixed concealed bracings in the wall, loading direction and the existence of the coupling beam structural steel have on the seismic behavior,This thesis focused on the force-displacement curves, ductility, Seismic parameter point, The stiffness degradation curve of the dual-chamber reinforce concrete core walls with mixed concealed bracings,the dual-chamber reinforced concrete core tube with X rebar concealed bracing and the ordinary dual-chamber reinforced concrete core tube. It has been proved that the whole forced condition and the seismic behavior have been greatly improved by adding concealed bracings especially mixed concealed bracings in the dual-chamber reinforced concrete core tube.Finally, this thesis mainly studies the relationship between the shear lag effect and the seismic performance of RC core tube. The results show that reducing the shear lag effect of core tube can greatly improve the mechanical properties and enhance the integrity and seismic performance of the RC core tube.