The deterioration of existing reinforced concrete (RC) structures is regarded as a problem worldwide. In Japan especially, the deterioration of RC dam structures has become severe. Many such dams meet design standards that were in place at the time of construction but do not meet the current seismic design standards, and appropriate seismic retrofitting is required. If the dam pier, which is an important part of the dam related to water storage, is damaged by an earthquake, the gate cannot be opened or closed, and the amount of water stored cannot be controlled. Therefore, the seismic retrofitting of dam piers is a top priority. However, various construction restrictions exist for dam piers, such as only the cross-section on the downstream side can be reinforced, and not on the upstream side where water is stored. Thus, it is difficult to apply the same reinforcement method that is applied to the piers of general road bridges. Therefore, in this study, we confirm the effectiveness of the SRS method (seismic retrofitting using cement mortar for shotcrete), which is suitable for partial reinforcement. Specifically, the dam piers of four types of existing dams were modeled using the three-dimensional finite element method, and a seismic response analysis was performed by inputting two types of seismic waveforms having different characteristics. As a result, the reinforcement effect of this method was verified according to structural characteristics. Furthermore, the effect of the reinforcement range on the reinforcement effect was clarified.

The limit state and deformation performance of steel bearing under seismic load is one of the most critical points to consider the effective or rational design of bridge against strong ground motion. In the 2016 Kumamoto earthquake, various bridges are damaged by the earthquake. Among the components of the bridge, steel bearings are the most damaged part of the bridge, which affects the functionality of the entire bridge. Since the 1995 Southern Hyogo Prefecture Earthquake, several studies about the ultimate state of steel bearing during earthquake carried out. However, there are a few studies on analyzing the failure processes and ultimate state of steel bearing when various loads assumed at the time of the earthquake. Therefore, the study investigates the failure process and ultimate state of pin bearing and pin-roller bearing under combined load using static push-over analysis. First, the bridge axis and perpendicular bridge axis horizontal loading directions proposed depending on the actual earthquake directional behavior of the bridge. Then the analysis of each bearing conducted and clarified the failure process of each bearing that leads to failure based on the von mises stress yield criteria. Three-dimensional finite element method used to analyze the bearings. The analysis result found that set bolt and pin neck tensile failure were the probable failure mode of pin bearing, and failure mode of pin-roller bearing depends on vertical and horizontal loading direction. In the future, the result used to propose a new seismic resistance design and reinforcement method of bearings that satisfies the required performance.

In this study, continuous fiber composite (CFC) panels were used as a strengthening material to improve the impact resistance of reinforced concrete (RC). Both experimental tests and numerical analyses were carried out to investigate the impact resistance of RC beams strengthened with CFC panels. The experiments involved repeated drop-weight impact tests at constant speed. The experimental results confirm that the strengthening of RC beams with CFC panels improves the impact resistance, thereby increasing the number of repeated impacts that can be allowed before a specified residual displacement is reached. In addition, a virtual particle model based on the conventional smoothed particle hydrodynamics (SPH) method, which takes into account the mechanical properties of the adhesive, was introduced as an analytical method to simulate the impact fracture behavior of RC beams strengthened with CFC panels. The analysis results show that the improved SPH method proposed in this study can accurately reproduce the impact behavior of RC beams strengthened with CFC panels and predict the allowable number of repeated impacts. Furthermore, a parametric study was carried out using a validated analytical approach to compare the load-bearing capacity and discuss the impact performance of RC beams with three types of CFC panel reinforcement.

Utility poles are widely utilized to support the distribution lines that deliver electricity produced at power stations to users. The need for utility pole maintenance has increased due to aging, and it is considered necessary to suggest standards and inspection methods for efficient maintenance. To improve the efficiency of pole maintenance, it is essential to organize the deterioration process and replacement indicators based on the structural dynamics of utility poles and suggest methods for evaluating deterioration using non-destructive testing. This paper summarizes previous technical trends and future issues regarding the efficient maintenance of utility poles by summarizing existing standards and research regarding deterioration factors, dynamic characteristics, and evaluation methods. As a result, for more efficient concrete utility pole maintenance, it is essential to collect data regarding the ultimate states of poles subjected to cyclic wind and earthquake loading over a long time and to analyze the correlation between the degree of damage and the data obtained by non-destructive inspection.

Medium-density polyethylene pipe has been widely introduced to low-pressure gas pipes because of its high flexibility and corrosion resistance. However, many third-party damages due to the impact of heavy equipment have been reported during the construction every year, thus, to prevent the third-party damage, materials such as high-density polyethylene and polyamide have been considered as the new gas pipe candidates. However, their impact resistance capacity under the third-party attack has not been clarified. In this study, static and impact loading experiments were conducted to compare load resistance capacities. As a result, it was revealed that the high-density polyethylene pipe and the polyamide pipe had higher static load capacity and impact resistance than the medium-density polyethylene pipe. By comparing the absorbed energy of the static test and the impact test and calculating the pseudo absorbed energy of the impact test, the evaluation formula judging the safer side of whether the penetration occurred was proposed. Furthermore, as one of the methods to protect the gas pipe, the protective effect of winding a sheet made of reinforced fiber and non-woven fabric was clarified.