These steel cables on suspension bridges and cable-stayed bridges are major members that transmit the dead and live load through the bridge’s main cable; hence, it is essential that inspection, maintenance and reinforcement are done regularly. In this study, we developed a magnetic sensor which is capable of detecting possible internal damages on bridge cables. It can be utilized to monitor actual suspension bridges and cable-stayed bridges.

A pipe-rack structure exposed to various environmental conditions is one of the critical structures for the safety of a plant industry. Based on a selected, typical pipe-rack structure, this study evaluated the behavior of the pipe-rack structure accounting for the operating condition of the pipe and at the same time the effect of environmental conditions.

Flood and scour are one of the major causes of bridge collapse. However, maintenance and inspection techniques still need improvements especially for underwater structures like bridge piers. Conventionally, manual inspection by divers has been carried out for underwater structures of bridges. This has difficulties in gathering accurate and reliable field data under severe environmental conditions. For this reason, underwater inspection is carried out using Side Scan Sonar(SSS) recently. The underwater structure image can be obtained by observing the reflected beam signal from underwater riverbed and surface. Signal and image processing techniques are employed in order to produce a clearer 2D image. Conventional inspection using one Side Scan Sonar is carried out to obtain river bed and underwater structure image. In order to reduce the inspection time, two Side Scan Sonar are used to obtain river bed and underwater structure image simultaneously. Two Side Scan Sonar were used to confirm the usability of the interference effects, which can occur by using the same frequency as the image at the time of collection, through indoor experiment for verification.

Maintenance of plant facilities are becoming important due to lots of recent plant construction. While maintenance of plant facilities are performed, maintenance of plant structures are usually not carried out properly. In this paper, measurement threshold estimation algorithm is developed for maintenance of pipe-rack structure. Currently, field verification of the developed algorithm is being performed on a real pipe-rack structure.

Recently, Maintenance and inspection of plant are now being actively studied with the development of plant industry. In this paper, A leak detection in piping facilities using thermal imaging camera is proposed. This method was verified by laboratory experiment. In future, Appropriate algorithm will be applied to this method for real time detection and finally applied to the plant that is the ultimate goal of this study.

Dynamic characteristics of large civil infrastructures have been monitored for safe operation and efficient maintenance of the structures. To measure vibration data, the conventional system uses cables causing very expensive costs and inconvenience for installation. Therefore, various wireless sensor nodes have been developed to replace the conventional wired system. However, there remain lots of issues to be resolved such as power supply, data loss, data security, etc. In this study, smart distributed sensor node (SDSN) was developed to measure vibration data. The SDSN is basically timely synchronized one-channel data acquisition system. It consists of its local time clock with high accuracy and SD memory card or local data storage. It is designed for temporal measurement, not long-term monitoring, since it can operate several hours using embedded batteries. Laboratoy tests were carried to verify the performance of the developed SDSN compared with conventional wired sensors. Several application examples for large civil infrastructure were also suggested.

In this study, an automated cable non-destructive test (NDT) system was proposed to monitor the steel cable. Magnetic Flux Leakage (MFL) method was applied for the cable inspection. A multi-channel MFL sensor head was fabricated using Hall sensors and permanent magnets. A wheel based Cable climbing robot was used to improve the accessibility to cable. In addition, remote data transmission and robot control were possible by applying the Wireless LAN communication. Finally, developed element techniques were integrated to MFL based Cable Climbing NDT system, and the field applicability of the integrated cable NDT system was verified through a field test.

The limit state design code for reliability-based design criteria was enacted in January 2012. And, it was necessary to consider new load carrying capacity method for new design code. Therefore, LRFR and ballowable stress design rating was applied to load carrying capacity and compared with the result. In addition, this research consists of ambient vibration measurement, experimental modal analysis, correction of the initial FE model based on the identified modal properties, and estimation of the load carrying capacity using the updated FE model

This study introduces an efficient image-based three-dimension motion tracking system for civil structures. The proposed system consists of hardware (four camcorders, a commercial PC and frame grabber) and software. The effective software and measurement scheme are developed to obtain the dynamic motion with six degrees of freedom. Several laboratory tests were conducted to verify the effectiveness of the proposed system with the maximum error of less than 3%.

Steel cables are frequently used for various infrastructures. Especially the steel cables in long span bridges are critical members Damage at cable members can occur in the form of cross sectional loss caused by corrosion and fracture. Therefore, NDE of steel cable is needed to measure the cross-sectional damage. In this study, Total Magnetic Flux sensor system was applied to monitor the condition of cables. This system measures total magnetic flux to detect the loss of metallic cross section area(LMA) of steel cable. To verify the feasibility of this study, 2 types of steel bar were fabricated and their output values measured by the search coil in total flux sensor.

In this study, an MFL(Magnetic Flux Leakage)-based NDT(non-destructive test) method was applied to detect the inner damages of steel cable. A steel cable bunch specimen with several types of inner damage was fabricated and scanned by a MFL sensor head to measure the magnetic flux density of the specimen.the measured magnetic flux signal was visualized into a 3D MFL image for convenient cable monitoring. Finally, the results were compared with information on actual inflicted damages to confirm the accuracy and effectiveness of the proposed cable monitoring method.

Since cable members are the major structural components in cable bridges, they should be properly inspected for surface damage as well as inside defects such as corrosion and/or breakage of wires. In this study, only the vision-based surface damage detection system based on image processing techniques is addressed. The damage detection programs are consist of real-time and post processing detection programs. The proposed damage detection programs were verified through laboratory tests on many types of cables.

In this study, a MFL (Magnetic Flux Leakage) image based 3D inspection system which is incorporated into a cable climbing robot was investigated for Steel Cable NDT of Cable-stayed Bridge and Suspension Bridge. Firstly, a MFL sensor head prototype composed of two permanent magnets and eight hall sensors was designed and fabricated. A steel cable specimen with several types of damage was inflicted and scanned by the MFL sensor head to measure the magnetic flux density of the specimen. The measured MFL signals were used to interpret the healthy condition of the steel cable. For improving the resolution and quantification of the damage level, digital signal processing techniques were performed. Finally, the measured MFL signals were visualized by using 3D imaging method.

By thermal-structural coupled stress analysis, the equivalent stress and total deformation of girder under the influence of the temperature of the liquid within pipeline of pipe-rack structure is studied. Firstly, steady-state thermal analysis is carried out using a commercial software. Then, to perform a thermal-structural coupled stress solution, structural analysis is linked to the thermal model at the Solution level. The simulation results showed that the stress ratio that considers the pipe’s temperature for thermal-structural coupled stress analysis is higher than the stress ratio that consider only the pipe’s weight for structural analysis. The thermal stress caused by temperature convection is found to be influential on the pipe rack structure.

Conventionally, the load carrying capacities of bridges have been evaluated from proof loading tests with test trucks by measuring static and dynamic response, such ad deflections or strains under known loading conditions. However, load carrying capacity of bridges was evaluated using the updated finite element (FE) model. To solve these problems, deflections or strains can not represent the bridge's health status as the bridge gets deteriorated. For example, deteriorated boundary condition results in small deflection or strain. The proposed method consists of ambient vibration measurement, experimental modal analysis, correction of the initial FE model based on the identified modal properties, and estimation of the load carrying capacity using the updated FE model. The proposed method has been verified through field tests on a prestressed concrete girder bridge by comparing with the result of the conventional truck loading tests.

In this paper, a research was performed to estimate dynamic characteristics of bridges using wireless sensors. First, the developed wireless sensors were compared with wired sensors through laboratory tests. Field tests were carried out on a steel box girder bridge. Dynamic characteristics of the test bridge were identified from the measured data by wireless sensors. As a result, it was proven that the wireless sensor system could be effectively applied to the measurement of large civil-infra structures.

This study introduces an algorithm for geometric distortion corrections in sonar images. The proposed algorithm mainly consists of two stages. At the first stage, the raw images are processed with median filter and Frost filter for noise reduction and intensity enhancement. In the last stage, the geometric distortion correction is conducted using angular information given by a gyro sensor. The algorithm was successfully applied on raw sonar data collected on a pier survey.

Damages due to typhoon and floods are increasing as a result of global warming and abnormal climate phenomenon over the world. Flood and scour is one of the major causes for bridge collapse. However, maintenance and inspection techniques still need improvements especially for underwater structures like bridge piers in rivers. Conventionally, manual inspection by divers has been carried out for underwater structures of bridges. This has difficulties in gathering accurate and reliable field data under severe environmental conditions. Therefore, in this study, underwater inspection of bridges has been carried out using the side scan sonar (SSS), one of unmanned underwater inspection equipment. Compared to the conventional manual inspection, it has been found that the SSS can be efficiently utilized to underwater inspection of bridges especially with bad visibility or large-scale inspection area.

최근 태국의 수도 방콕의 장기화된 홍수로 인하여 인명 및 국가 기간시설물에 대한 피해가 발생하였고, 전 세계적으로도 지구온난화 및 이상기후 현상으로 태풍 및 홍수에 대한 피해가 증가하고 있는 추세이다. 이로 인해 국내외에서 해마다 홍수로 인하여 많은 교량들이 붕괴되고 있으며, 교량파괴의 주요 원인은 홍수와 세굴인 것으로 분석되었다. 교량에서 중요한 부분인 교각처럼 수중에 위치한 구조물에 대해서는 결함을 찾아내고 이를 유지 관리하는 제반 기술적 사항이 미흡한 실정이다. 또한 교각수중점검을 수행하는 용역방식이 외부 비전문적인 용역방식과 인력 위주의 점검으로 인하여 안전관리 부재 및 점검자의 주관성 개입 등 데이터 획득과 결함 평가의 신뢰성에 나쁜 영향을 미치고, 형식적인 점검이 이루어지고 있는 실정이다. 따라서, 본 연구에서는 교량의 수중구조물점검을 위해 무인 수중 점검 장비 중 하나인 수중음파탐지기(Side Scan Sonar : SSS)를 이용한 실험으로 무인점검의 가능성에 대해 조사하였고 사용성 검증을 위한 수중촬영도 함께 실시하였다. 실험결과를 통해 Sonar를 이용한 교량 수중구조물 점검이 탁도가 불량이거나 대규모 교량의 세굴 탐지에 있어 효율적이라고 판단된다.