This study presents numerical analysis of elastic waves for detecting damage in epoxy adhesive zone. For the finite element analysis, a finite element program ANSYS LS-Dyna is used. The result signals of finite element analysis were analyzed by using pitch-catch method. It is shown that the received time signals successfully show the existence of defects

Part of the domestic construction practice and non-destructive inspection technology world level is often inadequate to provide the test results to serve as a basis for evaluating the safety of the structure. Therefore, in this study, is intended to provide basic data for legislation nondestructive inspection in Japan, estimates the size of the column using a technique reverberation impact manufactured column member or this purpose. 3% maximum error rate, the result was 1% minimum error rate. The average error rate is 1.6%, revealed as well as the size of the columns that have been measured

본 논문에서는, 모드유연도 행렬 기반의 손상추정 방법으로 제안된 normalized uniform load surface curvature (NULSC) 방법을 수치 해석 및 실험을 통해 검증하고자 한다. 기존의 모드유연도 행렬 기반 의 손상 추정 방법의 경우 구조물 응답의 크기가 작은 지점부 부근이나 모멘트 변화가 작은 지점에서 손상 추정에 어려움이 있다. 제안된 손상추정 방법은 기존의 손상 추정 방법인 ULS curvature 방법에 정규화 기법을 도입하여 손상 추정이 어려웠던 구조물의 지점부나 모멘트 변화가 작은 지점의 손상 추정이 가능하다. 제안된 손상 추정 방법은 단순보를 이용한 수치해석을 검증되었다. 단순보 모형을 이용하여 실내실험을 통해 제안된 방법을 검증하였다. 단순보의 단면 변화를 통해 단일 손상과 다중 손상을 모사했고 제안된 방법이 기존의 방법에 대해 손상을 민감하게 추정 하는 것을 확인 할 수 있었다.

This study presents a new estimation method for cable tension considering the initial deflection, the natural frequency changing, and the initial curvature shortening of an oscillating cable in the existing estimation formulas. The re-estimation for the cable-stayed Alamillo Bridge in Spain shows that the new procedure estimates tension force of the cables more accurately.

in this study, modulus of deflection and elasticity ware obtained by accomplishing field experiments to subgrade and subbase through LFWD equipment. Based on the interpretation of that results, we want to lay the foundation to utilize for compaction management of under construction and preventive maintenance management of after construction

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.

In this study, I tried to derive the expression intensity estimation through analyzing the correlation between wave velocity and compressive strength of high-strength concrete and normal-strength one, using ultrasonic pulse velocity which is one of the non-destructive tests which do not damage the structure. By producing a material age strength and body separate experiment which is applied to the ultrasonic pulse velocity, we have derived the estimating compressive strength such as a formula strength of normal-strength concrete : Fc=0.0841vp3.6018, R2=0.82 high strength concrete : Fc=0.0008vp6.9287, R2=0.88. As a result of this verification experiment, the estimated error rate of the compressive strength of normal strength concrete is 16.32%, in the case of high-strength concrete is now 7.58 percent.

10% drop of natural frequency from the initial healthy condition is reviewed to include the possibility of danger of foundation scour. To improve bridge safety management, legislations of measuring initial natural frequency, informing initial embedded depth, and systematic management of bridges under the control of the local governments are suggested.

Ultrasonic tests were carried out to establish the measurement conditions. As a result, the exponential transducer with 54㎑ and elastomer cover which were not nearly influenced by surface roughness were the most suitable for diagnosis of stone cultural heritages. In addition, the correction factors for indirect measurement were calculated as 1.52 for granite, 1.58 for quartz diorite, 1.38 for gabbro, 1.62 for sandstone and 1.69 for limestone. Based on the ultrasonic measurement conditions and the calculation methode of weathering index, the weathering degree of four Korean stone cultural heritages were evaluated. As a result, Sungnyemun stone block foundation was determined as the weakest heritage in relative and absolute weathering index

The durability of structures that has been built along the coastline based on the national geographic characteristics became a very important standard in economic and societal aspects. The environment that the steel corrosion would most likely happen is called tidal zone. It is a well-known zone and lots of researches have been done. We decided to implement steel corrosion monitoring on artificial seawater to find what kind of environment accelerates the steel corrosion. We compared and analyzed the experiment through galvanic potential measurement and half cell potential measurement

This study suggests a method for estimating embedded depth of a scoured bridge foundation using inverse analysis with natural frequency, that is a lot affected by soil stiffness around the structure. And applicability of the inverse analysis is performed by comparison of test results

Recent spread of awareness of residential environment and individual rights makes more environmental disputes than ever. More blasting is needed when construction projects like road, tunnel, railways and industrial area constructions. Noises and vibrations by blasting, therefore, cause many environmental disputes. In this study, we will suggest solution of environmental disputes deduction by case analysing.

Strain gauges is the most common device for measuring strain. Since the electric resistance of strain gauge changes only a little, strain gauges are almost always used in a bridge configuration with a excitation source. In this study, a strain measuring method, which calculate strain by reading a resistance of strain gauge, are investigated and verified.

In this study, we aimed to consider the inspection without destroying the specimen using the Impact Echo Method of nondestructive test using stress wave in an objective manner for detecting defects in concrete members. As a result of estimating the thickness of the concrete slab member using Impact Echo Method under the influence of the result of the stress wave, the average error in the 7.49% confirmed the applicability. In addition, we can check the possibility of data acquisition and construction of concrete structures for the construction of the diagnosis system

This study investigates wave propagation characteristics when guided waves propagate in a waveguide surrounded by non-homogeneous media. Assuming that the medium consists of same size elements, the acoustic properties of each element were determined using SWFEM method. The boundary conditions of each element and the waveguide were determined by random number.

In this study, a noncontact nondestructive testing (NDT) method is proposed to detect the fatigue crack and to identify the location of the damage. To achieve this goal, Lamb wave propagation of a plate-like structure is analyzed, which is induced by scanning laser source actuation system. The Lamb wave propagation is visualized and then damage is detected by wavenumber filtering method based on 3D FFT. Steel plates with fatigue cracks are investigated to verify the effectiveness and the robustness of the proposed NDT approach

Korea rapidly arranged urbanization and overpopulation with high growth of economy and all kinds of decrepit facilities are scattered all over the downtown. If there is a strong wind in fire, fire is rapidly increased by various fire spread factors. And Korea cannot build prediction model of urban fire combustion phenomena because there is no studies that physically explains the suitable flame phenomena for its real state. In this study, based on the Japanese Urban fire simulation to target the dense building and suitability of fire risk assessment were reviewed

This study investigated the House of Commons through the combustion characteristics of the flammable after performing the experiment for predicting fire constellation is to present basic material. Combustibles of the House of Commons was established to investigate through the standard model, such a list of proposed standards for the combustible

In this study, fire test of predicting fire behavior(fire growth rate, temperature of compartment, etc.) were performed for fire safety diagnosis in buildings. From this test, fire propagation for each combustible was identified, which was delayed compared to the summed heat release rate fo a single combustible. Also, comparison with Matsuyama model allowed improvement in the modeling of the process of fire spreading to nearby combustibles

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.