PURPOSES : This study aimed to develop high-performance concrete repair materials for the cross-sectional repair of deteriorated bridge concrete. METHODS : To derive the optimal mix using the dry shotcrete method, experiments were conducted to develop an appropriate performance in terms of durability and watertightness based on basic experiments on materials. By mixing silica fume, GGBFS, and natural fibers, this study compared the differences in each variable. Each variable was compared using compressive strength, flexural strength, plastic shrinkage, chlorine ion penetration resistance, and freeze-thaw tests. RESULTS : By mixing silica fume and natural fibers, watertightness and durability were secured, and by adding an expansion material and polymer powder, a material that exhibited suitable performance as a repair material was developed. The material demonstrated suitable performance in terms of compressive strength, freeze–thaw resistance, plastic shrinkage crack resistance, and chlorine ion penetration resistance. CONCLUSIONS : The repair material developed in this study has a higher performance than repair mortar, and because it uses a dry shotcrete method, the process and post-processing are simpler than the wet shotcrete method; therefore, it is believed to be more efficient for repair work.

PURPOSES : The wedge-type anchorage system requires a complex analysis of not only the tensile stress of the CFRP plate, but also the compressive stress and shear stress generated by the wedge action. The purpose of this study is to find a composite material failure theory that is suitable for analyzing the behavior of wedge-type anchorage system among various failure theories. METHODS : In this study, numerical analysis of various composite material failure theories was performed to analyze the anchorage strength and failure mode of the wedge-type anchorage system according to each failure theory, and compared with actual test results to determine the composite material failure theory most suitable for analyzing the behavior of a wedge-type anchorage system. RESULTS : Since the Maximum Stress failure theory shows similar results to the actual test in terms of failure mode and anchorage strength, there is no significant problem in applying it to the wedge-type anchorage system. However, it is judged to be difficult to apply under property conditions where interactions between stresses are highlighted. The Tsai-Hill and Tsai-Wu failure theories are considered unsuitable for application to wedge-type anchorage systems because the wedge angle conditions at which the most advantageous anchorage strength occurs are significantly different from other theories and the fracture type cannot be predicted. The Hashin-Rotem failure theory is considered to be the most appropriate to apply as a failure theory for the wedge-shaped anchorage system because the anchorage strength was slightly lower than the actual test results, but there was no significant difference, and the failure mode was consistent with the test results. The Hashin failure theory is judged to be unsuitable for application as a failure theory for the wedge-type anchorage system because the anchorage strength and failure mode were interpreted differently from the actual test results. CONCLUSIONS : The Hashin-Rotem failure theory was presented as the composite material failure theory most suitable for analyzing the behavior of wedge-type anchorage system.

PURPOSES : The purpose of this study is to conduct basic research on the development of repair materials for cross-sectional repair of the concrete of the lower slab ceiling of an old bridge. METHODS : To estimate the performance as restoration materials, cross section rebound test, compressive strength test, flexural strength test, and firing shrinkage test was done. Rebound test was done by weight of amount of rebound and weight of concrete accumulated in frame. Cross section rebound test was done by put ruler in the deepest part of concrete stick on frame. Compressive and flexural strength test was done based on KS F 2405 and KS F 2408. Firing shrinkage test was done based on ASTM C 1579-16. RESULTS : As a result of the experiment, an appropriate bonding thickness was secured by mixing natural fibers, polymers, early steel cement, and expansion materials, and the dust reducing agent was excluded due to the problem of lowering compressive strength. In addition, the amount of rebound was reduced by using a hydro mix nozzle, and plastic shrinkage cracks were also reduced due to the internal curing effect of natural fibers. CONCLUSIONS : This study was a basic study in the development of repair materials for cross-sectional repair of the lower ceiling of an aged bridge slab, and developed a material with appropriate performance. However, there is a problem that the amount of rebound and dust increases depending on the type of cement, so experiments will be conducted by changing the type of cement in future research.

도로 건설로 인한 서식지 파편화에 대한 저감방안으로 육교형 생태통로가 건설되고 있기는 하지만 효과성에 대해서는 아직도 논쟁이 있다. 생태통로의 효과성 평가를 위해 족적트랩, 카메라트랩과 같은 모니터링 방법이 실시되고는 있으나 얼마나 많은 개체가 이용하는지 정량적으로 평가하기에는 한계가 있다. 이에 본 연구에서는 생태통로와 인근 지역을 서식지로 이용할 가능성이 큰 소형포유류인 등줄쥐를 대상으로 포획-재포획 방법으로 개체 위치 파악을 통해 생태통로 이용 정도를 도출하고, 트랩 주변 환경 특성을 이용하여 등줄쥐의 생태통로 이용에 미치는 요인을 확인하였다. 등줄쥐의 생태통로 이용도는 격자 단위의 포획지점을 연결하여 이동 거리와 경로를 확인하였고, 생태통로 이용에 미치는 환경 특성은 트랩당 포획 횟수를 종속변수로 한 일반화 선형 모형(Generalized linear model)을 이용하였다. 연구결과, 등줄쥐의 이동 거리는 선행연구와 유사하게 나타났으며, 생태통로를 횡단하는 개체가 나타나지 않음에 따라 등줄쥐는 생태통로를 통로보다는 서식지로 이용함을 확인하였다. 등줄쥐가 생태통로를 이용하는 데 영향을 미친 환경 특성은 층위별 식생피복량(1~2m, 2~8m, 8m 이상), 교목 식생, 트랩 주변 최대 수목 흉고직경, 경사도가 유의하게 나타났다. 이에 따라 생태통로 조성 시 더 많은 교목과 관목을 식재하고, 높은 경사와 절토사면 생성을 방지하여 생태계 내 먹이원으로 이용될 수 있는 등줄쥐 이용도를 높인다면 생태통로의 효과성을 더 높일 수 있을 것으로 예상된다.

PURPOSES : The objectives of this study are to evaluate the condition of concrete bridge decks using the multi-channel ground penetrating radar (GPR) testing and compare the value of its dielectric constant value with actual concrete condition. METHODS : The reflection coefficient method was used to measure the dielectric properties of concrete bridge decks. Air-coupled step-frequency GPR testing was used to measure the time taken for reflection from the interfaces between the layers. Specimens of the asphalt mixture and concrete bridge-deck were collected by field coring. GPR testing was conducted on two bridges with different concrete bridge deck conditions on national highways. After the GPR tests, the actual conditions of the concrete bridge deck were investigated using specimen coring. RESULTS : GPR testing indicated that the dielectric constants of concrete bridge decks in good condition ranged from 8 to 10, whereas those corresponding to poor condition ranged from 4 to 6. The results of GPR testing can determine the actual condition and degree of distress of concrete bridge decks determined from the specimen coring data. Therefore, GPR testing is appropriate for nondestructively evaluating the condition of a concrete bridge deck. CONCLUSIONS : The analysis results of the dielectric constants of the concrete bridge deck obtained from multichannel GPR testing were consistent with the actual bridge deck conditions. In the near future, an additional verification process for this approach under different bridge conditions will be required to improve its precision and ensure reliability.

While social media marketing opens a variety of new windows for enlightening brand–customer relationships, a gritty puzzle is that brand recognition does not invariably echo with customers’ perceived value. This provokes the need to uncover the missing pieces in bridging the gap between brand recognition and customer perceived value. This research falls within the innovative new work in the marketing literature in positing co-creation as a crucial mediator in facilitating the impact of brand recognition on customers’ perceived value. Based on social identity theory, we also investigated how co-creation is moderated by virtual communication identification in influencing customers’ perceived value towards a brand. We conducted a survey via a sample of 386 current Gogoro customers. Gogoro is the biggest and most well-known Taiwanese producer of electric scooters. Our findings contribute to the extant marketing research by emphasizing that the key stimulus of increased customer perceived value towards a brand is active co-creation initiatives via virtual brand communities, and that the effects of co-creation are further strengthened when customers’ virtual communication identification is high.

In this study, computer simulation of the drawbridge structure was performed to verify the validity of the design and to evaluate its safety. For this, the follower bracket was modeled, and the parts of the follower bracket were connected using 1D elements. The boundary condition applied moments to the rotation shaft of the girder gear in the clockwise and counterclockwise directions, and the connection between the upper parts was modeled using 1D elements to model the bolted connection. In case of rotational shaft deformation, an analysis was performed on the displacement occurring in the structure during the opening/closing operation. As a result of structural analysis of the follower bracket for various cases, the stress at the connection was lower than the tensile strength and yield strength, so it was evaluated as safe. Through this, we intend to use it as a data that can identify anomalies.

본 연구에서는 마찰모델에 따라 다른 마찰진자시스템(FPS)이 적용된 교량의 성능을 비교･분석하기 위해 구조해석을 수행하였다. 마찰해석모델 별 성능을 분석하기 위해 PVDF/MgO 마찰재의 마찰계수를 활용하여 쿨롱 마찰모델과 속도 의존 마찰모델을 구축했다. 쿨롱 마찰모델은 마찰속도와 관계없이 단일 마찰계수를 사용하며, 속도 의존 마찰모델은 마찰속도에 따른 마찰계수의 변화를 반영하 는 마찰모델이다. 지진해석으로 비선형 시간 이력 해석과 지진 취약도 해석을 수행하여 구조물의 응답을 확인하였다. 마찰모델에 따 른 바닥판과 교각의 지진 응답을 활용해 면진된 교량의 성능을 분석하였으며, 면진된 교량의 성능을 효과적으로 평가할 수 있는 마찰 모델을 분석했다.

이 논문에서는 보행교의 진동 사용성 평가에 있어서 보행자의 이동 질량 관성 효과의 고려 여부, 보행 패턴 등을 고려한 보행 시나 리오 등에 따른 해석 결과를 제시하고, 그에 따라 보행교 설계 단계에서 동적 유한요소 해석을 통한 진동 사용성 평가에 있어 적절한 해석 방법과 유의점을 제안한다. 지간 40m의 강합성 박스 단면을 갖는 단경간 단순교 형식의 보행교에 대하여 보행자 밀도, 보행 속 도, 임의 보행, 동기화 보행 등을 고려한 보행 시나리오에 대한 가속도 응답을 분석한다. 해석 결과 고정 질량 해석 방법은 임의 보행 시 나리오 해석에서 이동 질량 해석과 큰 차이를 보이지 않으며 진동 사용성 평가시에는 더 넓은 진동수 대역을 가진할 수 있는 임의 보행 시나리오를 고려하는 것이 바람직할 수 있음을 보였다.

본 연구에서는 가설 강교에 사용되는 조립식 거더-교각 접합부에 대한 새로운 설계를 제안하였다. 새로운 접합부는 모듈의 각 부분을 공장에서 용접하여 제작한 후 현장에서 용접 대신 볼트 접합부를 사용하도록 구성하여 현장에서 모듈을 신속 하게 조립하도록 구성하였다. 이 새롭게 제안된 거더-교각 접합부의 구조적 성능을 평가하기 위해 정적 거동, 연성 성능 및 회 전 성능을 분석하는 실험을 수행하였다, 실험결과 제안된 볼트 접합부는 기존의 용접 체결부에 비해 정적 지지력, 연성 거동 및 회전 성능에서 우수한 성능을 보여주었다. 비록 볼트 체결부의 강성이 용접 체결부보다 다소 작지만, 체결부의 연성 성능이나 정적 지지력에 큰 영향을 미치지 않았으며, 안전성 향상, 빠른 조립 및 분해, 건설 공기 단축 등의 유리한 특성으로 인해 가설 교량 건설에 적합한 것으로 평가되었다.

이 논문에서는 기존의 조인트 교량을 일체식 교대 교량으로 변경할 경우, 온도하중에 의한 상부구조의 인장에 따른 흉벽의 휨거동을 보강하기 위한 흉벽 FRP 보강공법을 제안하고, 설계 및 유한요소해석을 통해 보강 효과를 검토하였다. FRP 보 강재는 펄트루젼 공정으로 제작하며, 흉벽 전면부에 부착하여 일체식 교대 교량으로 변경할 때, 흉벽에 부족한 인장철근의 역할 을 대체하게 된다. 흉벽 FRP 보강공법의 설계는 ACI Committee 440을 참고하여 수행하였으며, 유한요소해석은 콘크리트, 철근 및 유리섬유와 비닐에스터로 제작한 FRP 보강재의 최대응력을 보강 방법에 따라 비교하였다. 유한요소해석 결과, FRP 보강재는 콘크리트에 발생하는 인장응력을 감소시키는 역할을 하며, 흉벽이 저항할 수 있는 휨모멘트를 증가시킬 수 있는 것으로 나타났 다.