Working Mechanism Analysis On The Vertical Prolongation System With Steel Structure On The Top Of Original Reinforced Concrete Frame Structure

The dynamic parameters, such as mass, period, stiffness, damping ratios and so on will change, when multi-story reinforced concrete frame structure with steel structure adding on the top. Under this circumstansance the only analysis and design on the additional layers is unreasonable and unsafe. The analysis and design should be carried out on the overall structure.Zhengzhou Jinboda commercial center, with two additional stories on the top of the original four stories of reinforced concrete structure is chosen as the research object, and the engineering designing software PKPM is used to determine the dynamic parameters of the overall structure, then the simplified model of the representative structure is obtained. Finite element software ANSYS is applied to analyze the frequent and shear force of earthquake. A group of dynamic parameters are compared such as vibration period, displacement, the interlayer displacement angle, interlaminar shear and lateral stiffness and so on. By changing parameters, the main factors affecting the overall structure are discussed. The main conclusions are listed as following.The bottom shear force decreases gradually with the increase of layers on the top of the original structure. The second layer of the original structure becomes the weakest layer. Along with the increased in additional layer, the action of earthquake influence becomes more and more big.The maximum adding layer number is three for the original specimen structure of four-layer framework. For adding two-story steel structure of the overall structure, with the increased number of layers of the substructure, to have greater impact on the first layer of additional layer.For adding two-story steel structure of the original four-story structure, with the increased of the layer of the steel column section can reduce the first layer of the structure of the internal force. For this example project, the minimum cross-sectional dimension of the steel columns under seismic action should not be less than370X370×16×16mm.