• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.3
• /
• pp.76-85
• /
• 2017

In this study, to evaluate the mechanical properties of fiber-reinforced cement composites by strain rate, hydraulic rapid loading test system was developed. And compressive and tensile strength of the hooked steel fiber and polyamide fiber reinforced cement composite were evaluated. As a result, the compressive strength, strain capacity and elastic modulus were increased with increasing strain rate. The effect of compressive strength by type and volume fraction of fibers was not significant. The dynamic increase factor(DIF) of the compressive strength was higher than that of the CEB-FIP model code 2010 and showed a trend similar to that of ACI-349. The tensile strength and strain capacity were increased with increasing strain rate. The hooked steel fibers were drawn from the matrix. The tensile strength and strain capacity of hooked steel fiber reinforced cement composites were increased as the strain rate increased. The tensile strength and deformation capacity of the fiber reinforced cement composites were increased. And, hooked steel fibers were drawn from the matrix. On the other hand, because the bonding properties of polyamide fiber and matrix is large, polyamide fiber was cut-off with out pullout from matrix. The strain rate effect on the tensile properties of polyamide fiber reinforced cement composites was found to be strongly affected by the tensile strength of the fibers.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.6
• /
• pp.114-122
• /
• 2018

This study presents the emergency assessment method about seismic safety of cable-supported bridges using seismic acceleration sensors installed on the primary structural elements of them. The structural models of bridges are updated iteratively to make their dynamic characteristics to be similar to those of real bridges based on the comparison of their natural frequencies with those of real bridges estimated from acceleration data measured at ordinary times by the seismic acceleration sensor. The displacement at the location of each seismic acceleration sensor is derived by seismic analysis using design earthquake, and the peak value of them is determined as the disaster management criteria in advance. The displacement time history is calculated by the double integration of the acceleration time history which is recorded at each seismic acceleration sensor and filtered by high cut(low pass) and low cut(high pass) filters. Finally, the seismic safety is evaluated by the comparison of the peak value in calculated displacement time history with the disaster management criteria determined in advance. The applicability of proposed methodology is verified by performing the seismic safety assessment of 12 cable-supported bridges using the acceleration data recorded during Gyeongju earthquake.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.14 no.1
• /
• pp.229-238
• /
• 2013

The aim of this study is to evaluate university canadian paddlers' iso-kinetic muscle function and provide training advices. Eight university paddlers with a 8.5 years career participated in this study. Inbody 720, biodex system III, biodex stabilizer system and THP 2 are used to investigate body component, muscle function(peak torque, average power and work fatigue), agility and dynamic balance. Iso-kinetic muscle function around shoulder, thorax and knee are measured. And then bilateral and unilateral muscle imbalance are calculated at each joint. Results of this study are as follows; University canadian paddlers' BMI average is 24.90 $kg/m^2$ and percent body fat is 12.23%. Reaction time average was 324 msec and balance score at each leg are below 2.0. A3, A4, A5, A6, A8 are needed to train shoulder muscle strength and power. A1, A2, A7, A8 are needed to strengthen shoulder muscle endurance. A2, A5, A8 are needed to train thorax muscle strength and power. A1, A8 are needed to strengthen thorax muscle endurance. Most of paddlers' reciprocal muscle balance ratio on thorax and knee are out of normal range. A2, A3, A4, A8 are needed to train abdominal strength and A3, A5, A6, A7, A8 are needed to train hamstring strength.

• Journal of KIISE:Software and Applications
• /
• v.28 no.3
• /
• pp.211-223
• /
• 2001

본 논문에서 제안하는 시나리오기반 검증기법의 목적은 UML로 작성된 객체지향 분석모델의 완전성 및 일관성을 진단하는 것이다. 검증기법의 전체 절차는 요구분석을 위한 Use Case 모델링 과정에서 생성되는 Use Case 시나리오와 UML 분석모델로부터 역공학적 방법으로 도출된 객체행위 시나리오와의 상호참조과정 및 시나리오 정보트리 추적과정을 이용하여 단계적으로 수행된다. 본 검증절차를 위하여 우선, UML로 작성된 객체지향 분석모델들은 우선 정형명세언어를 사용하여 Use Case 정형명세로 변환하다. 그 다음에, Use Case 정형명세로부터 해당 Use Case 내의 객체의 정적구조를 표현하는 시나리오 정보트리를 구축하고, Use Case 정형명세 내에 포함되어 있는 객체 동적행위 정보인 메시지 순차에 따라 개별 시나리오흐름을 시나리오 정보트리에 표현한다. 마지막으로 시나리오 정보트리 추적과 시나리오 정보 테이블 참조과정을 중심으로 완전성 및 일관성 검증작업을 수행한다. 즉, 검증하고자 하는 해당 Use Case의 시나리오 정보트리를 이용한 시나리오 추적과정을 통해 생성되는 객체행위 시나리오와 요구분석 과정에서 도출되는 Use Case 시나리오와의 일치여부를 조사하여 분석모델과 사용자 요구사양과의 완전성을 검사한다. 그리고, 시나리오 추적과정을 통해 수집되는 시나리오 관련종보들을 가지고 시나리오 정보 테이블을 작성한 후, 분석과정에서 작성된 클래스 관련정보들의 시나리오 포함 여부를 확인하여 분석모델의 일관성을 검사한다. 한편, 본 논문에서 제안하는 검증기법의 효용성을 증명하기 위해 대학의 수강등록시스템 개발을 위해 UML을 이용해 작성된 분석모델을 특정한 사례로써 적용하여 보았다. 프로세싱 오버헤드 및 메모리와 대역폭 요구량 측면에서 MARS 모델보다 유리함을 알 수 있었다.과는 본 논문에서 제안된 프리페칭 기법이 효율적으로 peak bandwidth를 줄일 수 있다는 것을 나타낸다.ore complicate such a prediction. Although these overestimation sources have been attacked in many existing analysis techniques, we cannot find in the literature any description about questions like which one is most important. Thus, in this paper, we quantitatively analyze the impacts of overestimation sources on the accuracy of the worst case timing analysis. Using the results, we can identify dominant overestimation sources that should be analyzed more accurately to get tighter WCET estimations. To make our method independent of any existing analysis techniques, we use simulation based methodology. We have implemented a MIPS R3000 simulator equipped with several switches, each of which determines the accuracy level of the

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.1
• /
• pp.35-42
• /
• 2020

Torsional behavior due to the plane irregularities of the piloti building can cause excessive story drift in the torsionally outermost column, which can lead to shear failure of the column. As a seismic retrofit method that can control the torsional behavior of the piloti building, the expansion of RC wall, steel frame or steel brace may be used, but such methods may hinder the openness of the piloti floor. Therefore, in this study, linear dynamic analysis and nonlinear static analysis for piloti buildings retrofitted by knee brace were performed, and seismic performance evaluation and torsion control effect of knee brace were analyzed. The results showed that the shear force of the column increased when the piloti building retrofitted by knee brace, but it was effective in controlling the torsional deformation. In case of retrofit between knee brace and column by 30°, the shear force of the column increased less than that of 60°, and the lateral displacement of column was decreased in the order of □, ◯ and Ｈ in cross-section.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.23 no.1
• /
• pp.94-101
• /
• 2019

Most of the existing rail structures have undergone a lot of aging since a considerable period of time has passed from completion. In particular, among existing railway bridges, many of the plate girder bridges are older bridges that have lived 40 to 60 years or more. Since the treadmill is directly connected to the girder without the ballast, the running load of the vehicle is directly transmitted to the bridge. Therefore, the shock and noise applied to the bridge are larger than those of the ballast bridge, and the dynamic shock and vibration are also relatively large. Therefore, it is very urgent to develop appropriate maintenance, repair and reinforcement technology for existing steel plate bridge. In this study, the authors introduced the characteristics of embedded rail (ERS) developed for improving the performance of the existing plate girder bridge and the techniques solving the vibration and noise problems. In order to evaluate the vibration and noise reduction performance of ERS, a non-ballast plate girder bridge with 5m length of sleepers installed and a plate girder bridge with ERS were fabricated. And, then, the vibration response generated under the same excitation condition was measured and analyzed. Also, the radiated noise analysis was performed using the vibration response data obtained from the experiment as the input data of the acoustic analysis model. As a result of experiments and analyses, it was confirmed that the plate girder bridge's vibration using ERS was reduced by 15.0~18.8dB and the average noise was reduced by 7.7dB(A) more than the non-ballast bridge.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.1
• /
• pp.41-50
• /
• 2021

In this study, the flow path width (Gap Size), which is the flow path of fluid, was selected differently among various factors that determine the Ccontrol Force of MR damper, and the change of Control Force was confirmed accordingly. For this purpose, two MR dampers with a Gap Size of 1.0mm and 1.5mm were fabricated, respectively, and dynamic load experiments were conducted according to changes in applied current and vibration conditions The experimental results showed that the minimum Control Force was 3.2 times higher than 1.5mm in the case of 1.0mm Gap Size, and the maximum Control Force was 2.3 times higher than 1.5mm in the case of 1.0mm Gap Size. In addition, the increased width of the Control Force according to applied current was 34N for Gap Size 1.0mm, and 12.7N for Gap Size 1.5mm. As the gap Size increased, the overall Control Force and the increase in the Control Force by the applied current decreased. Next, the dynamic range, which is a performance evaluation index of the semi-active Control device, was 2.3 on average under 1.0mm condition and 2.8 on average under 1.5mm condition, confirming the possibility of utilization as a semi-active Control device.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.24 no.5
• /
• pp.126-134
• /
• 2020

In the case of an earthquake, the fluid storage structure generates hydraulic pressure due to the fluctuation of the fluid. At this time, the hydraulic pressure of the fluid changes not only the peaked acceleration of the earthquake but also the sloshing height of the fluid free water surface. Factors influencing this change in load include the shape of the seismic wave, the maximum seismic strength, the size of the fluid storage structure, the width of the structure, and the height of the fluid. In this study, the effect of the ratio between the height of the fluid and the width of the structure was investigated on the fluctuation characteristics of the fluid. 200mm and 140mm of fluid were placed in a water storage tank with a width of 500mm, and a real seismic wave was applied to measure the shape of the fluctuation of the fluid free water surface. The similarity between the experiment and the analysis was verified through the S.P.H(Smoothed Particle Hydrodynamic) technique, one of the numerical analysis techniques. It was confirmed that the free water surface of the fluid showed a similar shape, through comparison of experiment and analysis. And based on this results, SPH technique was applied to analyze the fluctuation shape of the fluid free water surface while varying the ratio between the fluid height and the structure width. An equation to predict the maximum and minimum heights of the fluid free water surface during an earthquake was proposed, and it was confirmed that the error between the maximum and minimum heights of the fluid free water surface predicted by the proposed equation was within a maximum of 3%.

• The Journal of the Korea institute of electronic communication sciences
• /
• v.17 no.1
• /
• pp.59-70
• /
• 2022

In this paper, we proposed an active fault tolerant control (AFTC) method for the position control of a quadrotor with complete loss of effectiveness of one motor. We obtained the dynamics of a quadrotor using Lagrangian equation without small angle assumption. For detecting the fault on a motor, we designed a fault detection module, which consists of the fault detection and diagnosis (FDD) module and the fault detection and isolation (FDI) module. For the FDD module, we designed a nonlinear observer that observes the states of a quadrotor based on the obtained dynamics. Using the observed states of a quadrotor, we designed residual signals and set the appropriate threshold values of residual signals to detect the fault. Also, we designed an FDI module to identify the fault location using the designed additional conditions. To make a quadrotor track the desired path after detecting the fault of a motor, we designed a fault tolerant controller based on the multiple sliding surface control (MSSC) technique. Finally, through simulations, we verified the effectiveness of the proposed AFTC method for a quadrotor with complete loss of effectiveness of one motor.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.26 no.1
• /
• pp.49-57
• /
• 2022

In order to efficiently analysis the stability of a slope, measuring the shear strength of soil is needed. The Standard Penetration Test (SPT) is not appropriate for a slope inspection due to cost and weights. One of the ways to effectively measure the N-value is the Dynamic Cone Penetration Test (DCPT). This study was performed to develop a minimized multi-function sensors that can easily estimate CPT values and Volumetric Water Content. N value with multi-fuction sensor DCPT showed -2.5 ~ +3.9% error compared with the SPT N value (reference value) in the field tests. Also, the developed multi-fuction sensor system was tested the correlation between the CPT test and the portable tester with indoor test. The test result showed 0.85 R2 value in soil, 0.83 in weathered soil, and 0.98 in mixed soil. As a result of the field test, the multi-function sensor shows the excellent field applicability of the proposed sensor system. After further research, it is expected that the portable multi-function sensor will be useful for general slope inspection.