본 논문에서는 콘크리트 구조물의 층상박리균열 위에서의 손상탐지에 효율적인 충격반향기법에 대해 영향을 끼치는 다양한 영향요소들에 대한 분석을 수행하였다. 충격반향기법에서의 균열 가시화를 위해 층상박리균열위의 동적거동 및 두께를 나타내는 휨 모드 및 충격반향모드(두께 모드)에 영향을 끼치는 균열의 폭/두께(a/h) 비, 균열위의 상대적 가진 점, 측정 점의 위치 등의 시험설정 변수 등을 매개변수적 유한요소해석을 통하여 조사하였다. a/h비는 2보다 클 경우 휨 모드가 지배적이었으며 작을 경우 두께 모드가 지배적이었다. 또한 가진 점, 측정 점 중 어느 하나만 균열 위에 존재할 때도 휨 모드가 지배적이었으며 균열 밖의 범위의 건전한 영역에는 가진 점, 측정 점이 모두 위치하여야 두께 모드가 지배적이었다.

According to Department of labor guideline “2012-104 (2012.9.26.)” This study is to suggest the basic information and the improvement for the application of risk assessment on a construction site by group interview & survey of construction worker who is the practice of the subject and then numerical analysis about awareness and action plan of Safety and health. The result of group interview and survey of construction worker, most of construction worker feel the danger during the work. Then construction worker analysis results that risk assessment helps to change & raise awareness of safety and reduce an industrial disaster. Easy Safety management activity such as TBM & safety education active will be necessary for safe worksite and then I suggest the TBT(tool box talk) active which combines TBM & safety education.

본 연구는 현재 상태에서 콘크리트 내부의 균열, 공극, 결함 등을 식별 및 판단하고 일반적인 초음파법 및 반발경도법 외에 S-wave 및 R-wave를 사용하여 미래의 머신러닝 기법의 적용 가능성을 설명합니다. 또한, 다양한 머신러닝 기법 중에서 서포트벡터머신(SVM) 및 인공신경망(ANN)을 사용하여 콘크리트 건전성 평가에 대한 모델 개발을 통해 실험데이터의 예측 결과에 대한 비교분석을 진행하였고 최종적으로 SVM 모델을 제시하였다.

This study describes the applicability of machine learning techniques using the measurements of non - destructive testing techniques to identify the strength of concrete in the current state and to predict future strength. We also want to develop analytical techniques suitable for the strength evaluation of concrete among various machine learning techniques.

This paper presents the results of an experimental test conducted subjected to blast loading of steel plates. An experimental results were compared with the simulation result derived in AUTODYN to validate the simulation method used in this study.

This study was performed to select the performance-based evaluation items of concrete retaining wall. This study used Delphi Technique. As a result of survey, this study gained 17 condition assessment items and 7 safety evaluation items at final round. The results will be utilized as the basis for the performance-based evaluation.

Multi-physics nondestructive evaluation(NDE) technologies were proposed for monitoring section-loss and breakage of strands and tendons in prestressed girders moved from an actual bridge. The primary NDE technologies include Magnetic flux(MFL), Electrical resisticity(ER), Half-cell Potential (HCP), and Linear-polarization(LPR).

Robotics-Assisted Bridge Inpection Tool (RABITTM) combines a capability of conventional non-destructive evaluation techniques for condision assessment of concrete bridge decks, including electrical resistivity (ER), ground-penetrating radar (GPR), Impact-echo (IE), ultrsonic surface waves (USW), and a high resolution digital camera. In this study, the RABITTM platform was used to evaluate delaminaitons in a concrete bridge deck in the laboratory.

This study presents a practical approach for imaging concrete pavement and bridge deck slabs for the presence of delamination defects. Air-coupled impact resonance (i.e. impact-echo) test data are presented as a fused image using stacked spectral C-scans of the tested deck surface. The low frequency (less than 6 kHz) dynamic vibrational response of delamination defects, principally caused by the behavior of flexural vibration modes, clearly and accurately reveals the presence of internal shallow delamination defects. Images are constructed with data from air-coupled impact resonance tests carried out on laboratory and field concrete deck samples and an in-service concrete bridge deck.

This study investigated the compressive strength of concrete by using ultrasonic pulse velocity method, and proposed the equation able to predict the compressive strength of concrete.

The pupose of this study is to evaluate compressive strength of concrete applying to dynamic modulus of elasticity. Using the method of fundamental transverse and longitudinal resonant frequencies for concrete specimens, elastic modulus of concrete was measured and the relationship between compressive strength and dynamic modulus of elasticity was predicted.

The results from air-coupled impact-echo(IE) tests into concrete slab should be interpreted and represented so that field engineers can effectively check the condition of the structure. To improve these issues, IE data in the form of “4-D spectrum plot” can be utilized to identify the information of concrete defects effectively. The concept of the 4-D plot is introduced, and the effects of image parameters (e.g. frequency range, transparency index) are experimentally investigated in this study.

The field application of air-coupled impact echo (IE) is evaluated in this study, where an actual in-service concrete bridge deck is tested. An IE test equipment set is deployed as part of an effort to develop new rapid measurement method. The IE data are presented as two-dimensional frequency maps. For verification of the location of shallow delamination damage, eight drilled core samples were extracted from the test area. The results show reasonably good agreement with the drilled cores.

Recently, air-coupled impact-echo (IE) tests for rapid damage detection in concrete structures have been popularly employed, but they typically require an acoustically shielded, high sensitivity, pre-polarized air-pressure sensor. In this study, two types of air-coupled sensors (condenser and dynamic microphones) and one contact sensor (displacement sensor) are evaluated with regard to characterization of delamination damage in a concrete slab using the IE method. The contact and contactless IE tests were carried out over a simulated slab with artificial delaminations. Results show that even the dynamic microphone successfully captures impact-echo signals in a contactless manner and without acoustic shielding.

Vibration resonance tests offer an efficient NDE method to identify and characterize shallow (near-surface) delamination defects that afflict RC structures. However, efficient implementation of effective modal analysis methods for this purpose is hindered by practical testing limitations. This paper studies vibration resonance data from square, rectangular, and circular near-surface delamination defects in concrete using air-coupled impact resonance test.