Study On Seismic Performance Of RC Frames Strengthened By Frp Based On IDA Method

During the frequent occurrence of earthquakes in recent years, people have paid increasing attention to the seismic performance of the existing RC structures since they suffered from more or less damages even collapses in earthquakes. In view of the real conditions, the earthquake grouping is also remarkably adjusted so as to improve their design requirements in the current Seismic Design Code for RC structures, China. Therefore, it is very necessary and significant to strengthen these RC frames in service which can not satisfy the present seismic design requirements.In recent years, the fiber reinforced polymer(FRP) has been widely applied in reinforced concrete frame structures due to its virtues, such as high strength, light weight, and easy construction. In most of the practical engineering structures, FRP is employed to improve the bearing capacity or ductility of the key components. However, there is no strengthening method based on FRP aim at the global structural level for RC frames in seismic repair design guidelines. Consequently, the study on the seismic performance and seismic fragility of the RC frame structures retrofitted by FRP takes a great significance for enhancing the seismic performance of the global RC frame structures and developing effective strengthen design methods in structural level.Based on a RC frame model strengthened by FRP, this thesis adopts the incremental dynamic analysis(IDA) method to study its seismic performance and seismic fragility. The main contents and the corresponding results are summarized as follows:(1) On the basis of OpenSees software platform, this thesis develop a finite element(FE) model to simulate a RC frame structure model before and after strengthening by FRP, which was designed by Reyes Garcia and tested on a shake table. The finite element model is validated by comparing the numerical results with the experimental data. The comparison shows a good agreement. This indicates that the developed numerical model is accurate and reliable, which can provide a solid foundation for the further simulation and theoretical analysis.(2) Four limit states are defined for the RC frame, strengthened by FRP. The seismic performance and seismic fragility of the strengthened RC frame structure are compared with these of original structure based on IDA method. The results show that, for RC frame structure strengthened by FRP, the weak story transfers away from the original position and deformation of the strengthened RC frame appears early to consume the seismic energy. Meanwhile, the bearing capacity and the ductility of the strengthened RC frame are improved and the anti-seismic capabilities are clearly enhanced.(3) The developed and validated FE model is used to simulate the seismic performance and the earthquake dynamic analysis of a six-storey RC frames structure. The seismic performance and the collapse-resistant capacity of are compared between the strengthened RC frame structure and the original RC frame structure, and the performance differences are also made between the different types of FRP. The results show that the FRP used in the strengthening schemes has little effect on the initial stiffness of strengthened RC frame structure, while it has great impact on the seismic performance. Finally, the thesis suggests that it just needs to strengthen the plastic hinge regions in the beam-column joints of the first three floors when the global RC frame structures are strengthened by using FRP.