| Frame-core wall structures with strengthened stories is one of the main structural system of high-rise buildings, a lot of high-rise buildings that have been built and under construction adopted this kind of structure system to enhance the ability of resisting lateral displacement of the structures. However, increasing the local stiffness of the structure at strengthened stories is very disadvantageous for the structure to resistance seismic, the failure mechanis under earthquakes of frame-core wall structures with strengthened stories is not clear. In this paper, the response of the reinforced concrete frame-core wall structure under earthquake was analyzed by using the general finite element analysis software ABAQUS, further more, the weak parts of the structure are simulated and analyzed by using the sub model technique. The nonlinear analysis of reinforced concrete structure was based on the concrete damage plasticity model, the concrete was divided into plain concrete and reinforced concrete according to the reinforcement of the structure, the tension stiffening effect of reinforced concrete is taken into account by adjusting concrete the tensile stress-strain curves, eliminated the effect of finite element size in a certain extent as well.A typical model of reinforced concrete frame-core wall structure with strengthened stories is designed, the finite element model was based on one framework of the structure model. By comparing the calculation results of different structure schemes, the influence factors of the lateral displacement of the structure are studied. And the stress and deformation characteristics of the stories near the strengthened story are analyzed based on sub model method. The differences between the elastic seismic response and the elastic plastic seismic response of the structure are studied. The distribution of the weak story of the structure was studied through elastic plastic time history analysis, the plastic strain and damage distribution of the weak layer are calculated based on sub model method. Furthermore, the deformation characteristics and the yield mechanism of stories near the strengthened story were studied based on sub model method, as well as the damage distribution of concrete. Finally, three more precise sub model of joints were established to simulate the failure process of reinforced concrete joints.The study shows that increasing the stiffness of the strengthened story can increase the resistance to lateral displacement stiffness of the structure under static load, while the resistance to lateral displacement stiffness of the structure is greater under dynamic loads when structures vibration on lower vibration mode. The elastic analysis shows that the stress distribution of the adjacent floor is changed by the strengthened story. And the elastic story drift angle changes obviously at the strengthened story, while the elastoplastic story drift angle changes more severely. The maximum elastoplastic story drift angle appears at the stories near the strengthened story, which indicates that these stories are weak stories. When the structure is under strong earthquake, the beams in strengthened story damaged more slightly than others, plastic hinges occurred in the ends of beams of the stories near the strengthened story one after another, the order and number of the plastic hinges are greatly influenced by the seismic wave. The concrete at connected joint of core and outrigger damaged seriously, and the concrete in the middle of shear wall may be damaged by the outrigger in it. The calculation results of the joint sub models show that, the beam broke first, then the column broke, but the column may break more seriously than the beam though the outrigger truss reinforced the beam, changing the stiffness relationship between beam and column. The calculation results show that the elastic and elastoplastic calculation results of the sub model are accurate, and the sub model technique can be used in the finite element analysis of the high rise building. |
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