Investigation On Seismic Behavior Of Earthquake-damaged Reinforced Concrete Frames Retrofitted With CFRP

Statistical data of historical earthquakes show that aftershocks often occur in a relatively short time after a strong earthquake.Structures will suffer different degrees of damage after an earthquake,while they will suffer one or several aftershocks with different magnitudes in a short time.This will make the damage more serious,and even cause structural collapse,thus causing a great threat to human life and safety.Therefore,it is necessary to retrofit such damaged structures to avoid the aggravation of secondary damage.At present,many experimental studies on CFRP-retrofitted damaged structures have been carried out at home and abroad,but these studies mainly focus on the seismic performance analysis of components after repair,and less on the overall structure,and even less on the numerical analysis.In this paper,the seismic behavior of CFRP-retrofitted earthquake-damaged reinforced concrete structures is studied by combining theoretical research and numerical analysis.The main research contents are as follows:（1）With the method of reducing elastic modulus of reinforcement and reducing concrete strength,a numerical analysis model was established by OpenSees（Open System for Earthquake Engineering Simulation）,which was verified by comaring with the experimental results,to realize the numerical simulation of the nonlinear hysteretic behavior of CFRP-retrofitted damaged reinforced concrete columns.（2）A 6-storey reinforced concrete frame was designed via PKPM software.The damage state of the structure was determined by elastic-plastic dynamic time history analysis,and the earthquake-damaged reinforced concrete frame was established according to the validated modeling method.At the same time,five kinds of CFRP retrofitting strategies were designed according to the damage state,and the numerical analysis model of CFRP-retrofitted was established.Pushover analysis and elastic-plastic dynamic time-history analysis were conducted to evaluate the effect of different retrofitting strategies on the seismic performance of structures from the perspective of certainty.（3）Based on Incremental Dynamic Analysis（IDA）results,the global collapse resistance of frame structures with and without retrofitting by CFRP was quantitatively analyzed,and the impact of different retrofitting strategies on the collapse resistance of earthquake-damaged reinforced concrete frame structures was compared,and their collapse margin ratios were analyzed.（4）The probabilistic seismic demand analysis of damaged structures and CFRP-retrofitted structures were carried out by cloud analysis,and the logarithmic linear relationship between seismic intensity measuresS_a and engineering demand parameters?_max was regressed.Then,the dynamic time history analysis of the structure model was carried out.According to the definition of the limit state of the structure,the seismic fragility analysis of the damaged frame structure wih and without retrofitting by CFRP was carried out based on the results of the seismic demand analysis obtained by the analytical method and the cloud analysis,and the influence of the retrofitting strategies on the seismic performance of the structure was evaluated.In summary,investigation on seismic performance of the CFRP-retrofitted reinforced concrete frame.was conducted.The results show that the retrofitting with CFRP can effectively improve the seismic performance of the damaged reinforced concrete frame structure.The results can serve as the theoretical reference and technical support for practical application to retrofit the earthquake-damaged reinforced concrete frame structure.