Research On Holistic Behavior Of Story-adding Building

The practice shows that it is a economical and rapid method to relieve the present imbalance between supply and demand when story-adding reconstruction on the existing building. Therefore, the theory and technologies of story-adding and alteration on existing building is a chief branch of structure engineering at present. The research on the connection method and performance of existing building with new added structure, and the holistic behavior of the story-adding building is significant and valuable to improve the development of the industry of the building reinforcement and reconstruction.According to the research on the working mechanism and function of the interface of the new-old concrete, rendered the method that not only setting horizontal roof beam on the interface of the new-old concrete, but also planting reinforcing bar on it. Using numerical analysis method to analyze the dynamic characteristics of three models and the dynamic response under three seismic waves for six stories disposable, four-story added to six-story building just with horizontal roof beam and its with horizontal roof beam adding planting reinforcing bar. obtained five conclusions: (1) Under the different frequencies, the adding-story building and disposable building's vibration mode have the same change law , the main deformation is shear deformation, but under the bonding layer with horizontal roof beam and planting reinforcing bar condition, structure amplitude is more close to the disposable building's;(2) The natural frequency of the adding-story building and disposable building are close to each other when sets horizontal roof beam and planting reinforcing bar on the interface of the new-old concrete. Because of the connection action of the chemically-planted steel bar, integral rigidity of the adding-story building and its distribution along the height direction is better than the adding-story building's integral rigidity just with horizontal roof beam on the interface.(3) When just sets horizontal roof beam and planting reinforcing bar, angle of floor displacement of bonding layer is close to the angle of floor displacement of disposable building, and the difference between floor displacement of bonding layer and floor displacement of disposable building is 5%, because of the connection action of the chemically-planted steel bar restricts the relative slip and the crack development, increased the cohesion on the interface, reinforced structure holistic behavior;(4) Stress in the beam-column joint of new-old structure bonding layer is larger, so the planting reinforcing bar in the beam end of the bonding layer should be increased.The further thoroughly studies on adding extra-floors spanning existing buildings,which have definite reference value for improving the strengthen design code of concrete structure and Technical code for adding stories of brick-concrete structures of buildings ,as well as similar project design and construction reference.