Seismic Performance Analysis Of Frame Structure After Adding Renovation

In recent years, in order to improve the use of building space, increase the urban plot ratio, reduce demolition reconstruction cost, it is more and more popular to add layer to existing buildings. However, there are a series of problems, such as the complicated structure stress, the force transmission is not clear and so on, the lack of complete calculation method and design code for the structural plus layer design and seismic evaluation is to be systematically studied. At present, the research of the existing building adding layer modification is mostly aimed at the plane rule symmetry and the seismic fortification intensity is not very high. There are few studies on the reconstruction of the existing buildings with irregular plane in high intensity area. In this paper, the seismic behavior of a reinforced concrete frame structure and its influence factors are analyzed, which can provide reference for the construction of the similar structure.For starters, some common methods of strengthening the existing building steel structures as well as some basic theoretical basis for the seismic performance analysis of existing buildings are discussed in this paper. Take a plane irregular reinforced concrete frame structure as the object In Tianshui, Gansu Province, according to the results of the test, through the PKPM building space model calculation, verify the original structure needs strengthening before adding layers. By analyzing the factors of seismic behavior change after adding stories to existing buildings, the software ANSYS is used to establish the 3 sets of reinforcement layer model.(1)Strengthen the original structure through three ways, change the original structure stiffness, according to the requirement of the transformation, then make the adding layer design to the three schemes.(2)Change the adding layer number of plan 2: add one layer, two layer, three layer respectively.(3)Change column connection of the first group model, make the stylopodium hinged. Modal analysis, spectrum analysis and time history analysis of the three sets of models are carried out. Investigate the influence on the seismic performance after adding layers to the original structure caused by structural stiffness, number of adding layers, damping ratio, column node form.From the seismic analysis of structure adding layer modification, we can come to the conclusion that the deformation of the structure after adding layer is "uneven", and when the foot node chooses the hinge, heterogeneity is bigger. With the increase of the layer number, the natural frequency decreases, the displacement of the structure layer, the displacement angle of the layer and the shear force all increase. However, due to the low number of layers, the effect of damping ratio on the results of structural spectrum analysis and time history analysis is little. When the overlay nodes is hinged column, the concrete frame structure layer displacement and interlayer displacement angle is similar to rigid column base, but the interlayer displacement angle between the upper layer and the steel structure will be exceeded. Therefore, for the reinforced concrete frame structure in high intensity area, column node should not be used. In the transformation of existing buildings, appropriately increasing the structural stiffness of the lower part can improve the seismic performance of the structure, pay attention to the increase and lower stiffness ratio. In the high intensity region of the existing building plus layer reconstruction, do not use the local layer.