• Journal of the Korean Society for Nondestructive Testing
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• v.30 no.6
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• pp.527-538
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• 2010

This paper presents a nondestructive evaluation approach for system identification (SID) of real railway bridges using field vibration test results. First, a multi-phase SID scheme designed on the basis of eigenvalue sensitivity concept is presented. Next, the proposed multi-phase approach is evaluated from field vibration tests on a real railway bridge (Wondongcheon bridge) located in Yangsan, Korea. On the steel girder bridge, a few natural frequencies and mode shapes are experimentally measured under the ambient vibration condition. The corresponding modal parameters are numerically calculated from a three-dimensional finite element (FE) model established for the target bridge. Eigenvalue sensitivities are analyzed for potential model-updating parameters of the FE model. Then, structural subsystems are identified phase-by-phase using the proposed model-updating procedure. Based on model-updating results, a baseline model and a nondestructive evaluation of test bridge are identified.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.15 no.2
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• pp.341-349
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• 2002

The radar method is becoming one of the major nondestructive testing(NDT) techniques lot concrete structures. Numerical modeling of electromagnetic wane is needed to analyze radar measurement results. Finite difference-time domain(FD-TD) method can be used to simulate electromagnetic wave propagation through concrete specimens. Five concrete specimens with different thickness are modeled in 3-dimension. Radar modeling results compare measurement results to find backface of the concrete specimens and measure thickness of the concrete specimens.

• Proceedings of the KSR Conference
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• 2007.05a
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• pp.1523-1526
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• 2007

This study introduces the testing results of the carbody. The load test was performed to evaluate the structural characteristic and stability of the stainless carbody. The carbody is made of stainless steel. The body structure consisted of side frame, under frame, roof frame, and end frame. Of these components, the side frame and under frame were the most important components considering the vehicle and passenger loads. Loading test were performed under the condition based on "Performance Test Standard for Electrical Multiple Unit". The test results showed that the body structure is safe and stable under the condition of designed load.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2011.10a
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• pp.72-77
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• 2011

In this study, the natural frequencies and mode shape of an external mounting pod were verified using the modal analysis and modal testing technique for a pod mounted on an aircraft. The procedure associated with the FEM building of an external mounted pod to predict the dynamic behavior of aircraft structures is described. The simplified FEM reflecting the results of the modal testing of a pod is built through the optimization, applied to the structural dynamic model of an Aircraft, used to verified the stability of vibration and flutter of an aircraft.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.10a
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• pp.460-465
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• 2000

In this study, a durability estimation system of turning centers is developed to systematically evaluate the effects of structural specification and testing condition on the durability. All loads such as weights, inertia forces, cutting force and so on, are automatically transferred from the upper elements to the lower elements by the force flow which can be derived from the structural code of turning center. And the external loads applying to the moving and rolling elements are determined by using the equilibrium conditions of force and moment. Especially, the durability of turning center is estimated based on the lifes of moving and rolling elements under the required testing condition.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.3
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• pp.230-234
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• 2009

As concrete ages, the surrounding environment is expected to have growing influences on the concrete. As all the impacts of the environment cannot be considered in the strength-estimating model of a nondestructive concrete test, the increase in concrete age leads to growing uncertainty in the strength-estimating model. Therefore, the variation of the model error increases. It is necessary to include those impacts in the probability model of concrete strength attained from the nondestructive tests so as to build a more accurate reliability model for structural performance evaluation. This paper reviews and categorizes the existing strength-estimating statistical models of nondestructive concrete test, and suggests a new form of the strength-estimating statistical models to properly reflect the model uncertainty due to aging of the concrete. This new form of the statistical models will lay foundation for more accurate structural performance evaluation.

• Journal of the Korea institute for structural maintenance and inspection
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• v.3 no.4
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• pp.205-214
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• 1999

구조물의 동특성(고유진동수, 감쇠, 모드형상 등)의 변화는 구조물의 안전도를 평가할 수 있는 한 방법이다. 본 연구에서 콘크리트 세그먼트의 웨브 부분에 상당히 많은 균열이 진전되고 있는 상태의 Post-Tensioned Segmental 콘크리트 교량의 안전도 평가를 시도하였다. 안전도 평가를 위한 근간 데이터로 1986년 측정했던 데이터와 2차원 유한요소해석에서 얻은 결과값을 사용했다. 손상의 정도와 손상의 위치를 보다 정확히 찾아내기 위한 기술 중의 한 방법으로 Modal Test를 이용하였다. 이 방법이 Post-Tensioned Segmental 콘크리트 교량에 적용되어 교량의 안전도를 분석 평가하였다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2016.05a
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• pp.91-92
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• 2016

Structural integrity of reinforced concrete structures including nuclear power plants needs to be evaluated on a regular basis. Deterioration inside the concrete structures can be represented by voids. In this study, the varied volume fraction of voids inside mortar specimens was studied as a parameter using ultrasonic testing equipments. Both direct and indirect measurement methods were employed. The results show that there is a clear distinction between the specimens with different void volume fractions.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.986-995
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• 2008

This study introduces the testing results of the AL car body which is applied to LRT. The LRT car body is made of aluminum structure materials like a sandwich panel. The static load test was performed to evaluate the structural characteristic and stability of the AL car body. Considering the vertical, compressive, twisting load and 3-point supporting, Bend natural frequency Measurement, Twist natural frequency Measurement type as a testing terms, the structural stability of a car body was evaluated.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2001.10a
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• pp.135-140
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• 2001

The radar method is becoming one of the major nondestructive testing (NDT) techniques for concrete structures. Numerical modeling of electromagnetic wave is needed to analyze radar measurement results and to study the influence of measurement parameters on the radar measurements. Finite difference-time domain (FD-TD) method is used to simulate electromagnetic wave propagation through concrete specimens. In the experiments, three concrete specimens are made with the dimensions of 100 cm (length) x 100 cm (wideth) x 14 cm (depth). Three specimens had a Dl6 steel bar at 8, 10, 12 cm depth.