No abstract

It is very important to investigate the effects of the seismic performance of corrosion-damaged reinforced concrete (RC) members, in terms of their strength and lateral deformability, on the seismic performance of entire building systems. Such investigation allows accurate evaluation of the seismic performance of RC structures with corroded members, including beams and columns. However, current techniques for evaluating the seismic performance of existing RC structures do not take the effects of deterioration (including the corrosion of reinforcing bars) on the performance of RC members into account. The main objective of this research is to propose a practical methodology for evaluating the seismic performance of RC buildings with corrosion-damaged members. We extrapolate a structural performance degradation factor from the strength-deformation capability of corroded members to allow direct quantitative evaluation of their seismic performance. In this study, as a first step toward achieving this goal, we experimentally investigated the effect of reinforcing bar corrosion on the behavior of RC beams and the structural performance degradation factor. Our analysis was based on the strength-deformation capabilities of corrosion-damaged beams. We also propose a relationship between the half-cell potential of corroded reinforcing bars and the structural performance degradation behavior of RC beams. Our results indicate that there is a relatively strong correlation between the performance degradation factor and the average potential difference, with coefficients of determination (R2) of the flexural and shear beams of 0.78 and 0.91, respectively. The potential difference, which was measured using the half-cell measurement method, can serve as one of the indicators of relative structural degradation, but we must ensure that the environmental measurement conditions are held constant.

The purpose of this study was to propose a method for evaluating the seismic capacity of existing RC buildings in Korea by reviewing the applicability of the Japanese Standard. Based on the seismic capacity of Korean buildings evaluated by this standard, we modified the basic structural index, which is calculated in terms of the ultimate horizontal strength and ductility. We compared our experiment results to the values calculated using the strength equations for columns and walls from the Japanese Standard. The flexural strength equations could be applied without modification, while the shear strength equations required modification. We evaluated these modified strength equations and proposed unit average shear stresses of columns and walls based on statistical data relating to the structural characteristics of Korean buildings. The values of the ductility indices, which are primarily calculated based on the shear-to-flexural capacity ratio, of Korean buildings with hoop spacing wider than 300 mm, as computed by the proposed method, were more reasonable than those calculated by the Japanese Standard. We believe that the proposed method provides a useful strategy for identifying Korean buildings that are vulnerable to seismic activity, and recommend urgent earthquake preparedness measures.

In this study, a seismic strengthening method by internally attaching steel frame was proposed for strengthening medium-to-low-rise reinforced concrete (RC) buildings. The main technique proposed in this study was a welding method for connecting between existing R/C frame and internal steel frame strengthening element. The connection technique was developed considering the structural integral behavior between existing frame and strengthening member. The method is one of the strength design approach by retrofit which can easily increase the ultimate lateral-load capacity of R/C buildings controlled by shear. The cycling load test, designed using an existing school building in Korea, was carried out in order to verify the seismic retrofitting effects of the proposed method in terms of the maximum load carrying capacity. The nonlinear static analysis was also conducted to establish a hysteresis model of the proposed strengthening method, and to investigate the consistency between experiment and analysis results. The results revealed that the proposed internal strengthening method installed in R/C frame enhanced conspicuously the strength capacities, and the test results can reasonably compared to those of the non-linear static analysis.

No abstract