| It has been confirmed by many investigations about rebar corrosion that chloride- ind uced corrosion of steel bars in reinforced concrete exposed to marine environments and deicing salts has become one of the major causes of deterioration in many existing reinforced concrete(RC) structures. It can lead to further structural distress duo to the loss of the reinforcing steel crosssectional area as well as loss of bond along the steel-concrete interface. As a result,the RC structure damaged by rebars corrosion suffered extensive structural damage and even collapse when subjected to a strong ground motion.Therefore, it is necessary to investigate the technique to strengthen the corroded column in order to upgrade the seismic performance. Based on that, the following aspects are carried out in this thesis:(1) With the method of electrochemical accelerated corrosion, ten reinforced concrete columns with corrosion rate at around 10% are produced, and the reinforced concrete samples are tested under the action of horizontal load, thus obtaining the skeleton curve and hysteretic curve of the corrosion components, which are then compared with the intact specimens. The results indicate that the bearing capacity, ductility and seismic energy dissipation of corroded reinforced concrete columns are 12%, 26.8%, 55% lower than those of the intact specimens respectively. And the corroded reinforced concrete column meets with brittle failure.(2) Through the low cyclic test, the anti-seismic performance of the CFRP concrete column is studied. Research parameters mainly include seismic damage degree, the influe nce of lateral rate. The results show that in the lateral rate 1% cyclic loading, the CFRP reinforced specimens energy capacity increased 65.4% and in the lateral rate 2% cyclic loading, the CFRP reinforced specimens energy capacity increased 235%. So CFRP fully play its role in the larger lateral rate. When the lateral load rate of 2%, reinforced specimens of earthquake damaged 30% reduced 54% in energy consumption than reinforced specimens of earthquake damaged 15%. With the extent of earthquake damage,the energy consumption of specimens reduced dramatically.(3) This study is aimed at improving this model with the consideration of low-cycle fatigue theory.The low-cycle fatigue life equation is introduced and correlation between the normalized deformation and the normalized limit of energy absorption for RC members under cyclic loading is investigated by means of regression analysis of the published test results.By multiplying another energy weighted coefficient, which is related to the loading path and can be calculated by the critical ductility factor and the equivalent energy factor,the modified ParkAng seismic damage model is obtained. Test and numerical simulation results show that the damage computed by the modified Park-Ang damage model is not more sensitive to the nonnegative parameter β than that by the Park-Ang damage model. Seismic damage indices of D =0.4 and D =0.8 are suggested as the threshold values for repairable damage and collapse damage respectively.(4) Open SEES are used respectively to simulate the skeleton curve of the rust column, and then it is compared with that obtained by experiment. When the lateral rate of the skeleton curve with the simulation mode is smal, the calculating skeleton curve is perfectly identical to the experimental one; but when the lateral rate is above certain limits, Open SEES fiber model that based on the assumed plane unit can not simulate the slip and liftoff between concrete and rebar. The calculating capacity plummets to the level of specimen not matching with the experiment. |
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