Study On Key Technologies Of Story-adding Reconstruction Of Reinforced Concrete Frame

Upper and lower parts of the structural system of story-adding in the existing reinforced concrete frame structure are different, so are material properties including quality, ductility, stiffness and so on. In the whole structural system, the steel structure has a large change with a small upper damping ratio and a larger lower part. Therefore, in the process of designing the floors, the overall structure of analysis and design should be taken into consideration, in particular the loading features' analysis under the earthquake.MIDAS software is used to model the whole model of story-adding structure, and the structural modal vibration mode is analyzed. The vibration mode decomposition response spectrum method is used to analyze the seismic response of the structure, and the time history method is used as a supplement. And then with the change the added floors' number, the loading trend of structure is analyzed and then the mechanical characteristics are summarized. Other factors that affect the seismic performance of the whole structure are studied, and the support and reinforcement are studied in order to enhance the bearing capacity and stability of the structural system.The structural analysis shows that: the period of the story-adding structure is prolonged, the structural system is flexible and the rigidity is reduced; The first vibration mode is translational vibration type, and the center of mass and the center of rigidity does not occur with larger offset, besides great damage does not occur in the strong earthquake; The maximum displacement angle occurs in the second layer of the original structure, the sixth layer and the three layer after layer, all of which are the weak layer of the whole structure; When the floor stiffness suddenly becomes smaller, the displacement angle increases, and the lateral displacement is poor, which shows "whiplash effect";after support is added to the floor, the stiffness and bearing capacity of the structure are improved, the period of the structure is reduced, and the displacement angle of the steel structure is well controlled.