• Steel and Composite Structures
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• 제22권2호
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• pp.449-472
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• 2016

This paper studies the seismic behavior of reinforced concrete (RC) walls with encased cold-formed and thin-walled (CFTW) steel truss, which can be used as an alternative to the conventional RC walls or steel reinforced concrete (SRC) composite walls for high-rise buildings in high seismic regions. Seven one-fourth scaled RC wall specimens with encased CFTW steel truss were designed, manufactured and tested to failure under reversed cyclic lateral load and constant axial load. The test parameters were the axial load ratio, configuration and volumetric steel ratio of encased web brace. The behaviors of the test specimens, including damage formation, failure mode, hysteretic curves, stiffness degradation, ductility and energy dissipation, were examined. Test results indicate that the encased web braces can effectively improve the ductility and energy dissipation capacity of RC walls. The steel angles are more suitable to be used as the web brace than the latticed batten plates in enhancing the ductility and energy dissipation. Higher axial load ratio is beneficial to lateral load capacity, but can result in reduced ductility and energy dissipation capacity. A volumetric ratio about 0.25% of encased web brace is believed cost-effective in ensuring satisfactory seismic performance of RC walls. The axial load ratio should not exceed the maximum level, about 0.20 for the nominal value or about 0.50 for the design value. Numerical analyses were performed to predict the backbone curves of the specimens and calculation formula from the Chinese Code for Design of Composite Structures was used to predict the maximum lateral load capacity. The comparison shows good agreement between the test and predicted results.

• Geomechanics and Engineering
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• 제12권4호
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• pp.723-738
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• 2017

Rock is a heterogeneous material, which introduces complexity in the analysis of rock slopes, since both the existing discontinuities within the rock mass and the intact rock contribute to the degradation of strength. Rock failure is often catastrophic due to the brittle nature of the material, involving the sliding along structural planes and the fracturing of rock bridge. This paper proposes an advanced discretization method of rock mass based on block theory. An in-house software, GeoSMA-3D, has been developed to generate the discrete fracture network (DFN) model, considering both measured and artificial joints. Measured joints are obtained from the photogrammetry analysis on the excavation face. Statistical tools then facilitate to derive artificial joints within the rock mass. Key blocks are searched to provide guidance on potential reinforcement measures. The discretized blocky system is subsequently implemented into a discontinuous deformation analysis (DDA) code. Strength reduction technique is employed to analyze the stability of the slope, where the factor of safety can be obtained once excessive deformation of slope profile is observed. The combined analysis approach also provides the failure mode, which can be used to guide the choice of strengthening strategy if needed. Finally, an illustrated example is presented for the analysis of a rock slope of 20 m height inclined at $60^{\circ}$ using combined GeoSMA-3D and DDA calculation.

• 한국정보처리학회논문지
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• 제6권4호
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• pp.968-976
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• 1999

현재 유편봉투의 상태를 점검한 후, 우편 자동처리 센터(우편집 중국)에서 거의 대부분 OCR(Optical Character Recognition)로 우편주소 및 우편번호를 판독하여 3 of 5 형광(발광) 바코드로 7자리를 인쇄하고, 바코드 구분기(Barcode Sorter)에서 우편물을 자동구분 처리하고 있다. 일반적으로 자동처리 중에 우편주소 및 우편번호 잘못 기재, 주소 및 바코드 인쇄품질의 불량 등에 의하여 오류로 구분되어지는 우편 물량은 전체 우편물량의 31∼35%를 차지하고 있다. 본 논문에서는 이러한 문제점을 해결하기 위하여 도입될 고객 바코드 인쇄제도를 지원하기 위한 우편용 3 of 5 고객 바코드 및 우편주소 검증시스템을 개발하였다. 고객 바코드 검증시스템은 정해진 규격에 의해 고객 바코드가 정확하게 인쇄되었는지 검사하는 검증자 3 of 5 고객 바코드 검증시스템, 바코드 판독결과에 의하여 우편주소가 올바르게 작성되었는지 검사하는 우편주소 검증시스템을 제공하는 것이다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.193-196
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• 2008

이 연구에서는 지진하중을 받는 철근콘크리트 보-기둥 접합부의 연성능력을 평가하였다. 철근콘크리트 보-기둥 접합부 설계는 보에 소성힌지가 발생하기 이전에 접합부가 파괴하는 경우와 보에 소성힌지가 발생한 이후에 접합부 또는 보가 파괴하는 경우로 구분하여 설계하고 있다. 지금까지의 대부분의 기존 연구는 접합부의 강도 평가에 중점을 두고 있으며, 접합부의 연성능력 평가에 대한 연구는 미흡한 실정이다. 이 연구에서는 접합부의 연성을 기둥, 보, 접합부 패널 부분으로 구분하여 각각의 부재가 보-기둥 접합부의 전체 연성에 미치는 영향을 평가하였다. 접합부 설계는 일반적으로 보에 소성힌지를 발생시키고 접합부를 포함한 기둥은 탄성 상태로 설계하므로 탄성해석에 의하여 기둥의 연성을 평가하였다. 접합부 패널은 보의 소성힌지의 변형에 의하여 영향을 받게 된다. 따라서 이 연구에서는 보의 소성힌지의 영향을 고려한 접합부 패널 연성을 평가하였다. 소성힌지가 발생한 보의 연성은 보-기둥 접합부의 연성능력에 가장 큰 영향을 미친다. 보의 연성은 보의 휨에 의한 영향, 철근의 뽑힘에 의한 영향, 소성힌지 구역의 축방향 변형률 증대에 의한 영향으로 구분하였다. 또한 접합부의 부착강도 저감 및 보의 주철근 항복 이후의 철근의 뽑힘 및 소성힌지 구역의 축방향 변형률 증대에 의한 영향을 고려하여 보의 연성능력을 평가하였다.

• 한국공간구조학회논문집
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• 제16권2호
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• pp.61-68
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• 2016

Behavior of RC(Reinforced-concrete) beam-column connections has been subjected to the earthquake loading has been determined by shear and attachment mechanism. However, since the shear and attachment are very fragile for cycle loadings. Through occurring plastic hinges at the beam, the column and the connection should remain elastic condition and the beam should dissipate the energy from the earthquake. This study was investigate on the seismic performance of 6 RC beam - column connections built with the high strength reinforcements (700MPa) based on design and detailing requirements in the ACI 318-05 Provision and KCI-07 appendix II. This is aimed to evaluate the effect of the high-strength reinforcements as used the beam-column connection members. The main comparisons were the seismic performance of the connections affect the seismic performance in terms of strength, stiffness and ductility, joint shear stress-strain. A total of 6 beam-column specimens were built with a 1/2 scale and subjected to the cyclic loadings. Main design considerations were the area of the longitudinal reinforcements of the beam and details of the beam-column joint designed based on the seismic code. Cyclic test results are given and recommendations for the usage of high strength reinforcements for the seismic design is provided.

• 한국기계가공학회지
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• 제16권5호
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• pp.13-18
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• 2017

In this work the augmented safety of Type 4 composite vessel in accordance with uniform-stress design has been demonstrated through a series of burst tests and structural analyses. For this end, three sample vessels were used: (1) designed as guided by the isotensoid dome theory (called iso-dome cylinder); (2) with dome longer compared to uniform-stress design (called prolate cylinder); and (3) with dome wider than uniform-stress design (called oblate cylinder). Structural analyses have been performed using ABAQUS finite element code based on the periodic symmetry to circumferential direction. As a result, the maximum stresses are induced around the bodies of all three cylinders. However, the analyses, with the assumption of possible defect demonstrate that the maximum stresses are induced around the dome knuckles for the prolate and the oblate cylinders. The results of the burst tests for the three cylinders show that the burst initiates from the cylinder body of the iso-dome cylinder and from the dome knuckles of the prolate and the oblate cylinders. Finally, it is recommended that, to comply with DOT CFFC 2007, the dome shape should be designed and fabricated as guided by the isotensoid dome theory.

• 한국강구조학회 논문집
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• 제19권5호
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• pp.435-454
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• 2007

본 연구에서는 국내 내진 설계규정에서 고려하고 있지 않은 근거리지진의 특성을 규명하고, 사장교 구조물에 미치는 영향을 검토하고자 한다. 대표적인 근거리 및 원거리지진의 실측자료를 선정한 후, 탄성 및 비탄성응답스펙트럼을 작성하여 지진기록의 특성을 분석하였다. 세 가지 형식의 사장교 및 실제 사장교 구조물을 대상으로 지진특성에 따른 응답해석을 수행하여 주요부재에 대한 응답특성을 비교 분석하였다. 또한 지진응답해석 결과를 이용하여 신뢰성해석을 수행하였으며, 신뢰성지수 및 파괴확률을 검토함으로써 대상 사장교 구조물의 내진 안전성을 정량적으로 평가하였다. 응답스펙트럼, 지진응답해석 및 신뢰성해석 결과에 의하면 근거리지진이 사장교 응답에 대한 영향은 기존의 원거리지진과는 상이한 양상을 보이고 있으므로, 사장교 구조물 설계 시 중요한 인자로 고려해야 할 것을 제시하고자 한다.

• Structural Monitoring and Maintenance
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• 제2권3호
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• pp.269-282
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• 2015

Civil structures should be designed with the lowest cost and longest lifetime possible and without service failure. The efficient and sustainable use of materials in building design and construction has always been at the forefront for civil engineers and environmentalists. Timber is one of the best contenders for these purposes particularly in terms of aesthetics; fire protection; strength-to-weight ratio; acoustic properties and seismic resistance. In recent years, timber has been used in commercial and taller buildings due to these significant advantages. It should be noted that, since the launch of the modern building standards and codes, a number of different structural systems have been developed to stabilise steel or concrete multistorey buildings, however, structural analysis of high-rise and multi-storey timber frame buildings subjected to lateral loads has not yet been fully understood. Additionally, timber degradation can occur as a result of biological decay of the elements and overloading that can result in structural damage. In such structures, the deficient members and joints require strengthening in order to satisfy new code requirements; determine acceptable level of safety; and avoid brittle failure following earthquake actions. This paper investigates performance assessment and damage assessment of older multi-storey timber buildings. One approach is to retrofit the beams in order to increase the ductility of the frame. Experimental studies indicate that Sprayed Fibre Reinforced Polymer (SFRP) repairing/retrofitting not only updates the integrity of the joint, but also increases its strength; stiffness; and ductility in such a way that the joint remains elastic. Non-linear finite element analysis ('pushover') is carried out to study the behaviour of the structure subjected to simulated gravity and lateral loads. A new global index is re-assessed for damage assessment of the plain and SFRP-retrofitted frames using capacity curves obtained from pushover analysis. This study shows that the proposed method is suitable for structural damage assessment of aged timber buildings. Also SFRP retrofitting can potentially improve the performance and load carrying capacity of the structure.

• Earthquakes and Structures
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• 제7권3호
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• pp.317-331
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• 2014

An experimental study was performed to investigate the seismic performance of solid steel reinforced concrete (SRC) frames with special-shaped columns that are composed of SRC special-shaped columns and reinforced concrete beams. For this purpose, two models of two-bay and three-story frame, including an edge frame and a middle frame, were designed and tested. The failure process and patterns were observed. The mechanical behaviors such as load-displacement hysteretic loops and skeleton curves, load bearing capacity, drift ratio, ductility, energy dissipation and stiffness degradation of test specimens were analyzed. Test results show that the failure mechanism of solid SRC frame with special-shaped columns is the beam-hinged mechanism, satisfying the seismic design principle of "strong column and weak beam". The hysteretic loops are plump, the ductility is good and the capacity of energy dissipation is strong, indicating that the solid SRC frame with special-shaped columns has excellent seismic performance, which is better than that of the lattice SRC frame with special-shaped columns. The ultimate elastic-plastic drift ratio is larger than the limit value specified by seismic code, showing the high capacity of collapse resistance. Compared with the edge frame, the middle frame has higher carrying capacity and stronger energy dissipation, but the ductility and speed of stiffness degradation are similar. All these can be helpful to the designation of solid SRC frame with special-shaped columns.

• Steel and Composite Structures
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• 제47권2호
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• pp.269-287
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• 2023

The WGJ420 fire-resistant weathering (FRW) steel is developed and manufactured with standard yield strength of 420 MPa at room temperature, which is expected to significantly enhance the performance of steel structures with excellent fire and corrosion resistances, strong seismic capacity, high strength and ductility, good resilience and robustness. In this paper, the mechanical properties of FRW steel plates and buckling behavior of columns are investigated through tests at elevated temperatures. The stress-strain curves, mechanical properties of FRW steel such as modulus of elasticity, proof strength, tensile strength, as well as corresponding reduction factors are obtained and discussed. The recommended constitutive model based on the Ramberg-Osgood relationship, as well as the relevant formulas for mechanical properties are proposed, which provide fundamental mechanical parameters and references. A total of 12 FRW steel welded I-section columns with different slenderness ratios and buckling load ratios are tested under standard fire to understand the global buckling behavior in-depth. The influences of boundary conditions on the buckling failure modes as well as the critical temperatures are also investigated. In addition, the temperature distributions at different sections/locations of the columns are obtained. It is found that the buckling deformation curve can be divided into four stages: initial expansion stage, stable stage, compression stage and failure stage. The fire test results concluded that the residual buckling capacities of FRW steel columns are substantially higher than the conventional steel columns at elevated temperatures. Furthermore, the numerical results show good agreement with the fire test results in terms of the critical temperature and maximum axial elongation. Finally, the critical temperatures between the numerical results and various code/standard curves (GB 51249, Eurocode 3, AS 4100, BS 5950 and AISC) are compared and verified both in the buckling resistance domain and in the temperature domain. It is demonstrated that the FRW steel columns have sufficient safety redundancy for fire resistance when they are designed according to current codes or standards.