Recently, measuring instruments for SHM of structures has been developed. In general, the wireless transmission of sensor signals, compared to its wired counterpart, is preferable due to the absence of triboelectric noise and elimination of the requirement of a cumbersome cable. However, in extreme environments, the sensor may be less sensitive to temperature changes and to the distance between the sensor and data logger. This may compromise on the performance of the sensor and instrumentation. Therefore, in this paper, free vibration experiments were conducted using wireless MEMS sensors at an actual site. Measurement was assessed in time and frequency domain by changing the temperature variation at(- 8℃, - 12℃ and - 16℃) and the communication distance (20m, 40m, 60m, 80m).

이 연구에서는 현장타설 캔틸레버공법(free cantilever method)을 적용한 PSC(prestressed concrete) 교량에 콘크리트의 장기거동을 고려한 시공 중 계측분석 방법을 제안하였다. 콘크리트 박스 거더의 장기 거동에 따른 응력을 확인하기 위해 온도센서와 변형률계를 함께 설치하고 계측된 데이터를 이용하여 크리프계수를 산출하였다. 또한 크리프계수를 적용한 콘크리트 박스 거더의 시공 중 응력을 분석하고 설치된 온도 센서의 변화 데이터를 비교하여 세그먼트 시공에 따른 연직변위를 분석하였다. 연구결과, 교량의 장기 거동을 고려한 FCM 교량의 시공 중 계측은 레이저 변위계나 처짐계를 사용하지 않고 온도와 변위 데이터만을 이용하여 효율적인 분석이 가능한 것으로 나타났다.

포장의 동결깊이는 30년간의 기온자료를 분석하여 만든 동결지수를 근거로 하여 동상방지층의 두께를 결정한다. 본 연구에서의 현장계측 지역은 동결지수에 따라 동결지수 550~650℃·일, 450~550℃·일, 350~450℃·일로 구분하여 지역을 선정하였고, 각 지역별로 절토부, 절성경계부, 저성토부(2m 이하 성토부) 구간으로 단면을 구분하였다. 각 단면에 동상방지층 유 무를 구분하여 포장층별로 계측기(온도, 함수비)를 설치하고 데이터를 수집하였다. 현장 모니터링 시스템을 통하여 수집된 데이터 분석을 통하여 포장된 도로의 동결깊이를 결정하는데 이용할 수 있다. 연구 결과, 동상방지층이 없을 경우 동결지수 550~650℃·일 지역에서는 대기온도에 따라 겨울철 노상층의 온도가 0℃ 이하로 나타났고, 동결지수 450~550℃·일 지역에서는 지역별로 상이했으며, 동결지수 350~450℃·일 지역에서는 동상방지층이 없어도 노상층의 온도가 0℃ 이하로 나타나지 않았다. 또한, 포장 단면별로 동결깊이를 비교한 결과 대기온도에 따라 동결깊이는 절토부가 가장 높았으며, 절성경계부, 저성토부 순으로 단면별 차이가 나타났다.

온도의 계측에는 열팽창(Thermal expansion), 열전기(thermoelectricity), 전기저항(resistance)등의 원리를 이용하고 있다. (1) 열팽창식 온도계 물체의 열팽창 원리를 이용하는 온도계에는 두 금속의 열팽창 계수의 차이를 이용하는 바이멜탈 온도계, 액체의 팽창을 이용하는 유리 온도계, 기체 압력이 온도에 비례하는 것을 이용하는 압력식 온도계 등이 있으나, 이중에서 유리 온도계가 가장 널리 사용되고 있다.(중략)

In this study, measurement temperature in the bridges was compared with temperature proposed by Korean design code. In addition, the structural analysis was performed in order to comparing the stress by measured thermal load and the stress by design thermal load. As a result, the stress that applied measurement temperature was evaluated larger than the stress that applied temperature proposed by Korean design code.

Recently, the event of slope failure has been occurring frequently due to rapid climate changes and broad development of infrastructures, and the research for establishment of monitoring and prevention system has been an attentive issue. The major influence factors of slope failure mechanism can be considered moisture and temperature in soil, and the slope failure can be monitored and predicted through the trend of moisture-temperature change. Therefore, the combined sensing technology for the continuous measurement of moisture-temperature with different soil depths is needed for the slope monitoring system. The various independent sensors for each item (i.e. temperature and moisture respectively) have been developed, however, the research for development of combined sensing system has been hardly carried out. In this study, the high-fidelity sensor combing temperature-moisture measurement by using the minimized current consuming temperature circuit and the microwave emission moisture sensor is developed and applied on the slope failure monitoring system. The feasibility of developed monitoring system is verified by various experimental approaches such as standard performance test, mockup test and long-term field test. As a result, the developed temperature-moisture combined measurement system is verified to be measuring and monitoring the temperature and moisture in soil accurately.

This study evaluates thermal movements of an existing bridge using digital image processing technologies. Digital images are acquired from smart phones. Thermal movements which extracted from bridge bearings' images are compared to the results of conventional displacement transducers. It is concluded that the image-based process for measuring thermal movements of bridges is accurate, practical and cost-effective.

It is very important to measure and monitor hull stress which is caused by a buoyant force and a weight of cargo for safety of ship. However, an exact measurement of hul stress, using the traditional strain gage which is made of metal or semiconductor, is very difficult, because a ship would be exposed by the severe temperature environment of -20 ℃ to 80 ℃. This paper propose a new concept strain gage which can improve accuracy and compensage effectively affects due to temperature. The strain gage is consists of two parts. One is the Hull Deformation Amplifier which introuce several lever and link system, and another is a transducer converting distance into voltage signal. The HDA measure the amount of deformation and amplify it. And a lever and link system of the HDA is introduced for compensating temperature deformation by installing in perpendicular direction without stress. This paper also reports on the results of the experiments to verify linearity of the strain gage.