This paper intends to analyze the behavior characteristics of steel storage racks according to the constraints conditions by external loads such as seismic loads. In order to achieve these goals, the steel storage racks generally used in Korea were selected as target structures and shaking table tests were conducted. In order to confirm the behavior according to the constraints conditions, the foundation of the steel storage racks was constructed with three conditions (1 bolt, 4 bolts, fixed) and the experiment was carried out. As a result of the analysis of the data obtained through the experiment, it was confirmed that additional damper installation is needed rather than changing the condition of the bottom plate in order to secure the safety of the steel storage racks.

If the MR fluid damper does not work, the magnetic powder (carbonyl iron powder) will sediment. To overcome this problem, we developed an EMR (Enhanced Magneto Rheological Fluid) fluid and evaluated control performance. For the dynamic load test using MR fluid and EMR fluid was conducted to evaluate control power and DR (Dynamic Range). In the damper performance test, the current was tested at intervals of 0.5A from 0.0A to 2.5A, and the control power of the EMR fluid was 84% compared to the control power of the MR fluid, The DR of the EMR Damper was 7.5. When the DR is 5.0 or higher, it is generally used as a semi-active control device. Therefore, the EMR fluid has proved its usability as a semi-active control device by showing 7.5 DR to 76% control performance of existing MR damper.

본 연구는 PVA(polyvinyl alcohol) 섬유와 VAE(vinyl acetate ethylene) 분말 폴리머를 사용한 시멘트복합체의 압축·휨강도 와 온도변화에 따른 충격파괴거동을 연구하였다. 충격시험은 -35℃, 0℃ 및 35℃의 선정된 온도조건에서 실시하였다. 본 실험에서는 시멘트 복합체와 일반 모르타르에 대한 충격파괴 에너지와 변위, 시간을 얻기 위해 낙하 충격시험기(Ceast 9350)를 사용하여 충격시험을 수행하였다. 강도 시험결과, PVA 섬유와 VAE 분말 폴리머의 휨강도는 모두 증가하였다. PVA 섬유보강 시멘트복합체의 경우 재령 28일에서의 압축강도는 약간 감소하였으나, 휨강도는 일반 모르타르 강도보다 24.4% 증가하였다. 낙하 충격시험 결과, PVA 섬유보강 시멘트복합체 시편은 섬유의 가교역할로 인한 균열발생의 억제와 에너지 분산에 의한 미세균열이 발생하였으며, 충격에 의한 배면파괴와 관통에 대하여 억제되었다. 반면 VAE 분말 폴리머 시멘트복합체와 일반 모르타르의 시편은 대부분 큰 균열이나 관통파괴 되었다. 충격하중을 받는 시멘트복합체와 일반 모르타르의 시편은 대부분 국부적인 취성파괴거동을 보이며, PVA 섬유보강에 의한 휨성능 증진으로 인해 충격에 대한 저항성능이 크게 향상되었다.

Among various image acquiring technologies which are based on electromagnetic waves, the frequently used imaging technologies in various industries and remote diagnostics, such as spectral, thermal, mm-wave, microwave and short-wave imaging are analyzed in their characteristics and their perspectives as the major diagnostic technologies in public safety areas are described.

This study is aimed at developing a wireless unified-maintenance system (WUMS) that would satisfy all the requirements for a disaster preventive SHM system of civil structures. The WUMS is designed to measure diverse types of structural responses in realtime based on wireless communication, allowing users to selectively use WiFi RF band and finally working in standalone mode by means of the field-programmable gate array (FPGA) technology. To verify its performance, the following tests were performed: (i) A test to see how far communication is possible in open field, (ii) a modal test on a bridge to see how exactly characteristic real-time dynamic responses are of structures. Finally, the WUMS is proved valid as a SHM, and its outstanding performance is also proven.

In this paper, a hydraulic damper was developed to protect the storage racks from earthquakes and the seismic performance of the storage racks was improved by applying the developed damper. In order to achieve these goals, the control capacity for the safety of the storage racks was determined, and a hydraulic damper satisfying the control capacity was designed and manufactured. In addition, the location of the hydraulic damper was determined through simulation. Finally, the shaking table test was carried out. As a result, the seismic performance improvement of the storage racks using the hydraulic damper was confirmed.

In this paper, real-time damage assessment technology was developed for detection the damage of bridges in real time and the performance of the developed technology was verified by vibration test. Real-time damage assessment technology was developed by combining statistical pattern recognition technology and simulation technology. In order to verify the developed technology, the earthquake response acquisition experiment was conducted according to the cable damage of the model cable-stayed bridge. As a result, it was confirmed that the developed real-time damage assessment technology can provide information on the location of damaged cable.

In this study, we adapted very low resolution (240x320 = 76,800 pixels) images by which it is difficult to detect cracks. An automatic crack detection technique has been studied using digital image processing technology for low resolution images of sewage pipeline. Authors have developed two algorithms to detect cracks. The third step covers an algorithm developed to find optimal threshold value, and the sixth step deals with algorithm to determine cracks. As the result, in spite of very low-resolution images, the performance of crack detection turned out to be excellent.

In this study, the SMG fluid was developed for compensating the defect of the MR Fluid that is commonly used in Semi-active control system. And the damper with SMG fluid have been developed for practical application. The dynamic load test was conducted to evaluate the control performance of the SMG damper at 0.5Hz and 1Hz frequency conditions and 0A and 0.5A current conditions. As a result, the remarkable performance of the SMG damper was verified.

This paper aims to develop a wireless unified-maintenance system(WUMS) to obtain real-time structural response of civil structures. The WUMS integrates the GPS module, the strain module and the acceleration module based on the standalone controller, and includes the RF module for remote measurement and the battery for long term operation. In order to evaluate the performance of the WUMS, a response test using a modal shaker and a modal test using a model bridge were performed. The test results using USMS were compared with those measured by wired system. Finally, the developed WUMS was appropriate to obtain the structural response of the civil structure in real-time, unified, and wirelessly.

This paper aims to developed SMC-Fractional algorithm, that is, enhances the performance of Sliding Mode Control(SMC) algorithm for pounding control of Multi-span bridges using MR-damper. The pounding control performance of SMC-Fractional algorithm has been evaluated in shaking table test on multi-span bridge. As a result of the experiment, the SMC-Fractional algorithm showed the performance od reducing the relative displacement of adjacent spans over other algorithms.

In this study, MR(Magneto-Rheological) Grease fluid was developed for compensating the settling phenomena of MR(Magneto-Rheological) fluid which is widely used in semi-active control system. In order to characterize the settling phenomena of the MRG fluid, the experimental comparison was conducted. The control performance assessment of the MRG fluid was also evaluated. As a result, it was verified that the MRG fluid have the sufficient performances to use as a material for semi-active control device.

This paper aims to develop a wireless unified-maintenance system(WUMS) to obtain real-time structural response of civil structures. The WUMS integrates the GPS module, the strain module and the acceleration module based on the standalone controller, and includes the RF module for remote measurement and the battery for long term operation. In order to evaluate the performance of the WUMS, a response test using a modal shaker and a modal test using a model bridge were performed. The test results using USMS were compared with those measured by wired system. Finally, the developed WUMS was appropriate to obtain the structural response of the civil structure in real-time, unified, and wirelessly.

This paper aims to developed SMC-Fractional algorithm, that is, enhances the performance of Sliding Mode Control(SMC) algorithm for pounding control of Multi-span bridges using MR-damper. The pounding control performance of SMC-Fractional algorithm has been evaluated in shaking table test on multi-span bridge. As a result of the experiment, the SMC-Fractional algorithm showed the performance od reducing the relative displacement of adjacent spans over other algorithms.

In this study, MR(Magneto-Rheological) Grease fluid was developed for compensating the settling phenomena of MR(Magneto-Rheological) fluid which is widely used in semi-active control system. In order to characterize the settling phenomena of the MRG fluid, the experimental comparison was conducted. The control performance assessment of the MRG fluid was also evaluated. As a result, it was verified that the MRG fluid have the sufficient performances to use as a material for semi-active control device.

This paper aims to develop a wireless multi-sensing system for structural health monitoring of civil structures. This system is designed to measure all kinds of data--static and dynamic response, etc--from a multi-sensing data logger, and to transmit the measured data by means of a wireless real-time RF module, and to analyze the transmitted data for a health monitoring of structure. To test its validity, a FE analysis of a model cable-stayed bridge has been conducted for system identification. And a modal test of the model bridge has been also performed by both the proposed system and a cable based commercial measurement system(IOTech) for comparison. Based on those results, the proposed system was found to have an excellent capability of measuring and transmitting data from actual structure, and thus to be applicable to health monitoring of civil structures.

This research is an experimental study attempting to use MR-dampers to control the complex behavior of multi-span bridge structures due to external loads such as seismic loads. For the purposes of this study, the model of components in each structure is identified, and then based on the results, a simplified system of the structure is derived. The performance of MR-dampers for complex behavior control is evaluated separately, according to the self-performance of MR-dampers and according to the performance based on applications of control algorithms. Based on the simplified system, Lyapunov control algorithm and Clipped-optimal control algorithm are applied. As a result, MR-damper is proven to be effective in the complex behavior control of multi-span bridge structures.

This study aimed to simulate the complex behavior of structures and predict test results. For this, the leading nonlinear model ‘Bouc-wen model’ was used, and rubber bearing and MR-damper were investigated. While seismic load was being applied, complex behavior of continuous structures was simulated. To test simulation performances, in addition, a seismic response test of the model structure was conducted using shaking table. Then, each structure’s displacement data were compared to simulation results. This study found that nonlinear model-based simulation results were mostly matched with test results, and they are applicable to the prediction of test results.

This study attempted to assess performances of adopted MR-damper to control the complex behavior caused by the interaction of independent continuous structures. For this, MR-damper (30kN) was designed and fabricated, and the MR-damper model was investigated using the Nonlinear Bingham Plastic Damper (NBPD). To assess experimental performances, a control test on the model structure was performed while El-centro 150% of seismic load was being applied. Then, MR-damper was placed between two independent structures to have it control independent displacement and complex behavior between the two structures. This study found that MR-damper is effective in controlling complex behavior of structures.

This paper aims at featuring dynamic characteristic of 2-span bridge by means of an cochlea-inspired artificial filter bank(CAFB), for the purpose of effective acquirement of real-time valid dynamic(acceleration) responses. Through dynamic testings performed on a model of 2-span bridge, its dynamic characteristics were featured on natural frequency. They were evaluated in comparison to wired measurement responses. Finally, the dynamic wireless measurement system on the basis of CAFB were found technologically and economically effective by obtaining valid dynamic(acceleration) responses whose size was compressed over the frequency range of interest.