In the fire there are fusion signs and damage by fire, and insulation aging and carbonization of the electric wiring in the ignition spot because of special characteristic of the appliance in the electricity fire. Because of the physical factor applied in the damage of fire, the decision of ignition spot by eye investigation is insufficient. In this paper, the cause of electricity fire is researched. The focus is on the operation state of operated MCCB(Molded Case Circuit Breaker) at the time of electricity fire. Through grasping the operation principle of MCCB and the experiment, the state of MCCB after fire suppression is discriminated. The distinction possibility on the exist of electricity fire is proposed.

The purpose of this study is to assess a fire-damaged concrete structure using a digital camera and image processing software. To simulate it, mortar and paste samples of W/C=0.5(general strength) and 0.3(high strength) were put into an electric furnace and simulated from 100 ℃ to 1000 ℃. Here, the paste was processed into a powder to measure CIELAB chromaticity, and the samples were taken with a digital camera. The RGB chromaticity was measured by color intensity analyzer software. As a result, the residual compressive strength of W/C=0.5 and 0.3 was 87.2 % and 86.7 % at the heating temperature of 400 ℃. However there was a sudden decrease in strength at the temperature above 500 °C, while the residual compressive strength of W/C=0.5 and 0.3 was 55.2 % and 51.9 % of residual strength. At the temperature 700 ℃ or higher, W/C=0.5 and W/C=0.3 show 26.3% and 27.8% of residual strength, so that the durability of the structure could not be secured. The results of L*a*b color analysis show that b* increases rapidly after 700 ℃. It is analyzed that the intensity of yellow becomes strong after 700 ℃. Further, the RGB analysis found that the histogram kurtosis and frequency of Red and Green increases after 700 ℃. It is analyzed that number of Red and Green pixels are increased. Therefore, it is deemed possible to estimate the degree of damage by checking the change in yellow(b* or R+G) when analyzing the chromaticity of the fire-damaged concrete structures.

The current fire-damage inspection and safety diagnosis has not developed from the labour and time-consuming method. Data collected through traditional safety inspection and survey methods are less quantitative and causes irregularity to the database; thus data becomes impractical for long-term maintenance and analysis. Data by 3D Scanning are more precise and quantitative in calculating the damages by a fire, the amount to repair and reinforce; furthermore, in evaluating the safety of the structure.

콘크리트 구조물이 화재 손상을 입을 경우 노출온도 및 지속시간에 따라 구조물의 심각한 성능 저하를 야기하며, 콘크리트의 재료 물성 저하를 수반한다. 화재 손상을 입은 콘크리트 구조물의 재사용여부 및 보수보강 판단을 위해서는 손상 직후 및 재양생 조건에 따른 주요 손상 부위의 면밀한 손상 평가가 필요하다. 본 연구에서는 재양생 조건에 따른 화재 손상을 입은 콘크리트의 재료물성 회복에 관한 실험적 연구 를 수행하였다. 화재 손상을 입은 콘크리트 시편을 상대습도 및 재양생 기간을 달리한 재양생 조건을 적용하였으며, 충격공진기법을 도입하여 콘크리트 시편의 화재 손상 전후 및 재양생 이후의 동탄성계수를 측정하여 손상 정도를 평가하였다. 측정된 결과로부터 재양생 조건 중 높은 상 대습도 조건에서 지배적으로 재료물성의 회복이 발생하였다. 추가적으로 콘크리트 시편의 동탄성계수 및 인장강도의 직접적인 비교 및 선형 회귀분석을 수행하여 재양생 조건에 따른 영향을 분석하였으며, 이를 토대로 높은 습도 조건에서 동탄성계수의 회복이 인장강도에 비해 두드 러지게 나타남을 확인하였다.

The purpose of study is to investigate properties of high strength concrete in fire. Composite fibers that are mixed in concrete are used to improve vulnerable point. The role of each fiber is to prevent of spalling effect and improve of flexural strength.

When concrete is exposed to extrem fire, its strength and durability degrades. The fire-induced damage in concrete is investigated at microscale and a nondestructive testing for the damaged concrete is presented.

In this study, the applicability of impact-echo method for assessment of residual strength of fire-damaged concrete is investigated. A series of standard fire test is performed to obtain fire-damaged concrete specimens. Impact-echo tests are executed on the specimens and the responses are analyzed. Compressive strengths of the fire-damaged concrete are evaluated and correlated with the ultrasonic wave velocities determined from the impact-echo responses. The effectiveness of impact-echo based ultrasonic wave velocity measurement for assessment of residual strength of fire-damaged concrete is discussed.