During maintenance, we closely examined the reinforced section where concrete has cracked at the time of cable installation. We confirmed that there has not been any sight of new cracks or growth of existing cracks. For the following year of Investigation, we plan to conduct close inspection of the reinforced section.

Improved measurement and structural modeling analysis of result, an improved method is very efficient. The difference of about 10~15% comes out, Improved measurement and structural modeling analysis of result, it is determined that the need for additional research, such as a change of the modeling subdivision, load contions.

Recently, to assessing the deflection of structural member, video gauge was widely used in the field of structural maintenance. This paper is dealt with the laboratory experience on the video gauge for detecting the structural deflection from the digital Image. In this paper, real deflection from LVDT detected from model bridge in laboratory was compared with the measurement of the Video Gauge. The accuracy of the deflection measurement using the Video Gauge in the load of the bridge was verified.

In this study, impact elastic-wave method was performed at the bottom surface of RC slab cut from an existing highway bridges to survey the horizontal cracks. Before measurements by impact elastic-wave method, impact response analysis was applied to determine optimal steel ball diameter, distance between impact point and receiving point of elastic-wave. Efficiency of analysis-aided impact elastic-wave method was confirmed by drilling and observing the interior of the RC slab by stick scanner. Evaluation results by this method agreed well with results of visual inspection. Thus, validity of the analysis-aided impact elastic-wave method on detection of horizontal cracks in RC slabs of highway bridges was demonstrated.