Seismic Analysis And Concept Design Of Non-Ductile Rc Frames Retrofitted By CFRP

The non-ductile reinforced concrete (RC) frames refer to the frames that bears only vertical load and wind load, none considering seismic load, and the frames that cannot satisfy the present seismic requirements due to the revision of design code. These kinds of structures lack of enough ductility and energy dissipation capacity, so there is high risk of collapse in future earthquake events. Many of existing RC frames that designed according to the old design code needs to be strengthened for reducing the risk of structural collapses during earthquakes.The objective of this study is to evaluate analytically the seismic performance of retrofitted non-ductile RC frames with different height using Carbon Fiber-Reinforced Polymer (CFRP). Pushover and time history analysis were conducted for the studied cases. On the basis of analytical results, the concept design principle of CFRP retrofitting non-ductile RC frames is proposed. The investigation of this study is the basic work for presenting the seismic retrofitting design method of non-ductile RC frames using FRP wraps and significantly for developing and improving of the seismic retrofitting design code of concrete structure in our country. The main contents of the thesis are summarized as follows:1. The finite element analysis software Perform-3D was used to conduct Pushover and time history analysis. To validate the capacity and accuracy of the analyzed results, firstly a quasi-static cyclic test and a shaking table Benchmark test were simulated using the software, respectively. The comparisons between the test results and predictions of Pushover and time history analysis demonstrate the capacity and excellent accuracy of the software.2. Three non-ductile RC frames with different heights representing low- (5 floors), medium- (10 floors), and high-rise (15 floors) buildings as control specimens were designed and investigated Then the finite element model of three non-ductile frames and retrofitted frames using different rehabilitation patterns were modeled in Perform-3D. The seismic performance of the control and retrofitted RC frames was evaluated using the Pushover and dynamic time history analysis.3. The retrofitted effectiveness of different rehabilitation patterns is evaluated from the comparing of seismic performance control and retrofitted frames. It is found that the bearing capacity and the ductility of RC frames are improved after retrofitting, while the elastic stiffness is unchanged. The weakness floors may be transferred for retrofitted frames and then change the failure mode of retrofitted frame. The retrofitted effectiveness is best when retrofitting the low-rise frames. For the low-rise frames, the FRP rehabilitation of columns only is effective in enhancing the seismic performance and retrofitting both beams and columns perform the same as retrofitting columns only. For medium- and high-rise ones, rehabilitation of columns only cannot improve the seismic performance of frames and it is necessary to retrofitting both the frame beams and columns for these frames.