• Earthquakes and Structures
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• 제24권4호
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• pp.259-274
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• 2023

In this paper, mechanical properties of periodic foundation made of concrete and rubber are investigated by a parametric study using the finite element method (FEM). Periodic foundation is a special type of seismic isolation foundation used in civil engineering, which is inspired by the meso-scale structure of phononic crystals in solid-state physics. This type of foundation is capable of reducing the seismic wave propagating though the foundation, therefore providing additional protection for the structures. In the FEM analysis, layered periodic foundation is frequently modelled due to its simplicity in numerical modeling. However, the isolation effect of periodic foundation on nuclear power plant has not been fully discussed to the best knowledge of authors. In this work, we construct four numerical models of nuclear power plant with different foundations to investigate the seismic isolation effects of periodic foundations. The results show that the layered periodic foundation can increase the natural period of the nuclear power plant like traditional base isolation systems, which is beneficial to the structures. In addition, the seismic response of the nuclear power plant can also be effectively reduced in both vertical and horizontal directions when the frequencies of the incident waves fall into some specific frequency bandgaps of the periodic foundation. Furthermore, it is demonstrated that the layered periodic foundation can reduce the amplitude of the floor response spectrum, which plays an important role in the protection of the equipment.

• Steel and Composite Structures
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• 제42권1호
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• pp.91-106
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• 2022

Concrete-filled square stainless steel tubes (CFSSST), which possess relatively large flexural stiffness, high corrosion resistance and require simple joint configurations and low maintenance cost, have a great potential in constructional applications. Despite that the use of stainless steel may result in high initial cost compared to their conventional carbon steel counterparts, the whole-life cost of CFSSST is however considered to be lower, which offers a competitive choice in engineering practice. In this paper, a comprehensive experimental and numerical program on 24 CFSSST stub column specimens, including 3 austenitic and 3 duplex stainless steel square hollow section (SHS) stub columns and 9 austenitic and 9 duplex CFSSST stub columns, has been carried out. Finite element (FE) models were developed to be used in parametric analysis to investigate the influence of the tube thickness and concrete strength on the ultimate capacities more accurately. Comparisons of the experimental and numerical results with the predictions made by design guides ACI 318, ANSI/AISC 360, Eurocode 4 and GB 50936 have been performed. It was found that these design methods generally give conservative predictions to the ultimate capacities of CFSSST stub columns. Improved calculation methods, developed based on the Continuous Strength Method, have been proposed to provide more accurate estimations of the ultimate resistances of CFSSST stub columns. The suitability of these proposals has been validated by comparison with the test results, where a good agreement between the predictions and the test results have been achieved.

• 시큐리티연구
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• 제17호
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• pp.173-193
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• 2008

본 논문에서는 지속 가능한 도시개발과 범죄예방전략과의 상호 연관성을 중심으로 논의한다. 건강 안전도시에 따른 지속 가능한 도시발전에는 규제라는 이미지, 혹은 개인의 건강과 지역사회 안전에 실질적인 위협이 되는 범죄 및 범죄 두려움에 대한 합법적 통제라는 이미지를 내포하고 있다. 도시설계자들은 도시 환경에 대하여 지속 가능한 도시발전에 대한 개념을 인식하고 이를 실제 범죄예방전략으로 적용하려는 노력을 시도하고 있다. 많은 도시설계자들은 도시 환경의 개선을 통해 범죄 발생 및 범죄에 대한 두려움을 감소시켜 줄 수 있는 가능성에 대하여 연구하여 왔으며, 이에 대한 선행연구의 결과들은 방범환경설계(CPTED)의 적용을 통한 범죄 및 범죄 두려움 저감에 대한 구체적인 내용들을 보여주고 있다. 본 논문에서는 최근 우리나라에서 활발히 논의되고 도시관리 측면에서 적용되고 있는 범죄예방전략의 하나인 CPTED가 보다 더 안전하고 지속 가능한 도시사회를 만드는데 유용한 전략이 되기 위하여 필요한 정책적 대안을 제시하고자 한다.

• 융합보안논문지
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• 제11권5호
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• pp.109-120
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• 2011

기상상황은 고금을 통해 인간의 생활이나 병법의 중요한 요소로 생존전략의 핵심적 역할을 해왔다. 현대 도시의 과밀집중현상은 여러 가지 문제를 야기하고 있으며, 고층화와 토지피복의 변화는 기상의 이상 현상을 일으키는 작용을 하고, 특히 도심지역의 바람길은 주변의 지배적인 기상여건과 다른 흐름이 나타나고 있다. 따라서 바람길은 도심지역에 위치한 국가 중요시설 등에 대한 위기관리를 위한 방어계획에 중요한 고려 요인이 될 수 있다. 특히 대기 중에 유출된 유독물질의 유해성은 비람길이 핵심적인 변인이 된다. 본 논문은 도심지역의 바람길의 산출과 이를 통한 국가 중요시설 및 지역에 대한 위기관리에 유용성을 논의하고, 방어계획의 수립에 활용하기 위한 방안을 도출하고자 하였다. 이는 화생방테러리즘이나 폭력적 집회 시위에 대한 방어계획의 수립, 대형 사고나 자연재난 시 주민대피계획의 수립에 유용할 것으로 사료된다.

• 한국멀티미디어학회논문지
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• 제10권12호
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• pp.1671-1678
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• 2007

In these days, Disaster Management Systems have still put emphasis on its recovery more than the prevention of disaster events. However, the countermeasure of restoration has limitations to prevent the caused loss because the disasters often happen and are massive. Therefore, we propose a disaster prevention system for supporting the safe urban. In this paper, we try to construct a real-time monitoring system to prevent disaster events using new technologies such as Wireless Sensor Networks (WSN) and Geographic Information System (GIS). As a prototype to simulate the fire disasters on real-time, we construct gas sensors and temperature sensors. Our system consists of a WSN system to collect data of the gas and temperature sensors and to monitor the situation information. Our contribution is to provide a prototype application to prevent the disasters from the fire by constructing a WSN system with gas and temperature sensors.

• Computers and Concrete
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• 제19권4호
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• pp.387-394
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• 2017

To study the effects of water-cement ratio changes and cracks on chloride ion transmission rate in cracked concrete, RCM method was adopted to accelerate the diffusion of chloride ion in cracked concrete, and the changes in chloride ion concentration and around the cracks are inferred by finite-element method. The test results show that as far as prefabricated cracks on concrete components are concerned, the width thresholds of two cracks on the concrete specimens with a water-cement ratio of 0.5 and 0.6 are 0.05 mm and 0.1 mm respectively, the width threshold of two cracks on the concrete specimens with a water-cement ratio of 0.4 is 0.05 mm and 0.2 mm respectively; and the results of numerical simulation show that the smaller the water-cement ratio is, the more significant effects of cracks on chloride ion transmission rate are. As a result, more attention shall be paid to the crack prevention, repairing and strengthening for high-strength concrete.

• Earthquakes and Structures
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• 제7권3호
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• pp.251-269
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• 2014

To investigate the seismic performance and to obtain quantitative parameters for the requirement of performance-based bridge seismic design approach, 12 reinforced concrete (RC) hollow rectangular bridge column specimens were tested under constant axial load and cyclic bending. Parametric study is carried out on axial load ratio, aspect ratio, longitudinal reinforcement ratio and transverse reinforcement ratio. The damage states of these column specimens were related to engineering limit states to determine the quantitative criteria of performance-based bridge seismic design. The hysteretic behavior of bridge column specimens was simulated based on the fiber model in OpenSees program and the results of the force-displacement hysteretic curves were well agreed with the experimental results. The damage states of residual cracking, cover spalling, and core crushing could be well related to engineering limit states, such as longitudinal tensile strains of reinforcement or compressive strains of concrete, etc. using cumulative probability curves. The ductility coefficient varying from 3.71 to 8.29, and the equivalent viscous damping ratio varying from 0.19 to 0.31 could meet the requirements of seismic design.

• Structural Engineering and Mechanics
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• 제71권6호
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• pp.683-697
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• 2019

The reinforced concrete (RC) structures usually suffer large residual displacements under strong motions. The large residual displacements may substantially reduce the anti-seismic capacity of structures during the aftershock and increase the difficulty and cost of structural repair after an earthquake. To reduce the adverse residual displacement, several self-centering energy dissipation braces (SCEBs) have been proposed to be installed to the RC structures. To investigate the seismic responses of the RC structures with SCEBs under the earthquake excitation, an extended Bouc-Wen model with degradation and self-centering effects is developed in this study. The extended model realized by MATLAB/Simulink program is able to capture the hysteretic characteristics of the RC structures with SCEBs, such as the energy dissipation and the degradation, especially the self-centering effect. The predicted hysteretic behavior of the RC structures with SCEBs based on the extended model, which used the unscented Kalman filter (UKF) for parameter identification, is compared with the experimental results. Comparison results show that the predicted hysteretic curves can be in good agreement with the experimental results. The nonlinear dynamic analyses using the extended model are then carried out to explore the seismic performance of the RC structures with SCEBs. The analysis results demonstrate that the SCEB can effectively reduce the residual displacements of the RC structures, but slightly increase the acceleration.

• Earthquakes and Structures
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• 제16권6호
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• pp.641-654
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• 2019

This paper investigates the seismic response of a typical non-navigable continuous girder bridge isolated with friction sliding bearings of the Hong Kong-Zhuhai-Macao link projects in China. The effectiveness of the friction pendulum system (FPS) and accuracy of the numerical model were evaluated by a 1/20 scaled bridge model using shaking table tests. Based on the hysteretic properties of friction pendulum system (FPS), double concave friction pendulum (DCFP), and triple friction pendulum system (TFPS), seismic response analyses of isolated bridges with the three sliding-type bearings are systematically carried out considering soil-pile interaction under offshore soft clay conditions. The fast nonlinear analysis (FNA) method and response spectrum are employed to investigate the seismic response of isolated offshore bridge structures. The numerical results show that the implementation of the three sliding-type bearings effectively reduce the base shear and bending moment of the reinforced concrete pier, at the cost of increasing the absolute displacement of the bridge superstructure. Furthermore, the TFPS and DCFP bearings show better isolation effect than FPS bearing for the example continuous girder bridge.

• Geomechanics and Engineering
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• 제37권1호
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• pp.1-8
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• 2024

Buckling failure is one of the classical types of catastrophic landslides developing on inclination-paralleled rock slopes, which is mainly governed by its self-weight, earthquake and ground water. However, nearly none of the existing studies fully consider the influence of slope self-weight, earthquake and ground water on the mechanical model of buckling failure. In this paper, based on energy equilibrium principle and elastoplastic slab theory, a thorough mechanical analysis on bucking slopes has been carried out. Furthermore, an analytical solution for slip bucking failure of rock slopes has been proposed, which fully considers the effect of slope self-weight, seismic force and hydrostatic pressure. Finally, the methodology is used to conduct comparative analysis with other analytical solutions for three practical buckling studies. The results show that the proposed approach is capable of providing a more accurate and reasonable evaluation for stability of rock slopes with potential buckling failure.