Research On Nonlinear Analysis Methods Of Reinforced Concrete Tube In Tube Structure

Structural failures in recent earthquakes have exposed weakness of current design procedures. Along with the further development of human practice and earthquake resistant engineering technology, seismic design theory has also been changing and improving from time to time. Under such background, the scholars of the United States and Japan have proposed the philosophy of Performance-based Earthquake Engineering (PBEE) design, the basic thought of which is making the structure designed satisfied with the expected performance objects during the lifetime.Elastic-plastic analysis is an important part of performance-based seismic design. Among the existing methods, nonlinear static analysis (Pushover) method and incremental dynamic analysis (IDA) method which is based on dynamic time history analysis are regarded as the commonly used analysis methods of structural performance evaluation.The main studies and contents in this paper are as follows:Several simplified analysis models of shear wall are introduced. Comparative analysis are performed through an example to verify the effectiveness of those models in the elastic stage. Then we choose one of those models which is called the frame-brace model and try to simulate the elastoplastic properties of the shear wall by setting plastic hinges in the model.Based on the traditional pushover analysis, a modal pushover analysis is introducer in this paper and the basic theory and procedure of the method are described in detail. A process of using the MPA method to perform pushover analysis on two frame structures with different building height is carried out. The result shows that the MPA method can improve the calculation error caused by the traditional single lateral load pattern effectively and accurately.The basic principle, the parameters selection, the statistical methods and the definition of the limit-states of IDA curves for the IDA method are introduced in detail. The calculation process of the IDA method through the responses of a 14-story RC tube in tube structure is realized and the multiple earthquake records IDA curves is obtained. The limit-state capacities and different fractile IDA curves are also obtained according to the statistical method. Because the IDA of the practical structure is extremely time-consuming, two simplified and approximate methods of IDA are introduced in this paper: the IDA method based on modal pushover analysis and the IDA method based on SPO2IDA software. Then a comparative analysis is performed through example to judge the efficiency and the accuracy of the two methods.