• Structural Engineering and Mechanics
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• 제17권3_4호
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• pp.357-378
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• 2004

Nonlinear dynamic analysis of a reinforced concrete (RC) frame under earthquake loading is performed in this paper on the basis of a hysteretic moment-curvature relation. Unlike previous analytical moment-curvature relations which take into account the flexural deformation only with the perfect-bond assumption, by introducing an equivalent flexural stiffness, the proposed relation considers the rigid-body-motion due to anchorage slip at the fixed end, which accounts for more than 50% of the total deformation. The advantage of the proposed relation, compared with both the layered section approach and the multi-component model, may be the ease of its application to a complex structure composed of many elements and on the reduction in calculation time and memory space. Describing the structural response more exactly becomes possible through the use of curved unloading and reloading branches inferred from the stress-strain relation of steel and consideration of the pinching effect caused by axial force. Finally, the applicability of the proposed model to the nonlinear dynamic analysis of RC structures is established through correlation studies between analytical and experimental results.

• Earthquakes and Structures
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• 제13권2호
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• pp.177-191
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• 2017

In the present study, exterior beam column sub-assemblages are designed in accordance with the codal stipulations prevailed at different times prior to the introduction of modern seismic provisions, viz., i) Gravity load designed with straight bar anchorage (SP1), ii) Gravity load designed with compression anchorage (SP1-D), iii) designed for seismic load but not detailed for ductility (SP2), and iv) designed for seismic load and detailed for ductility (SP3). Comparative seismic performance of these exterior beam-column sub-assemblages are evaluated through experimental investigations carried out under repeated reverse cyclic loading. Seismic performance parameters like load-displacement hysteresis behavior, energy dissipation, strength and stiffness degradation, and joint shear deformation of the specimens are evaluated. It is found from the experimental studies that with the evolution of the design methods, from gravity load designed to non-ductile and then to ductile detailed specimens, a marked improvement in damage resilience is observed. The gravity load designed specimens SP1 and SP1-D respectively dissipated only one-tenth and one-sixth of the energy dissipated by SP3. The specimen SP3 showcased tremendous improvement in the energy dissipation capacity of nearly 2.56 times that of SP2. Irrespective of the level of design and detailing, energy dissipation is finally manifested through the damage in the joint region. The present study underlines the seismic deficiency of beam-column sub-assemblages of different design evolutions and highlights the need for their strengthening/retrofit to make them fit for seismic event.

• Geomechanics and Engineering
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• 제12권1호
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• pp.139-160
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• 2017

The bearing mechanism of tunnel-type anchorage (TTA) for suspension bridges is studied. Model tests are conducted using different shapes of plug bodies, which are circular column shape and circular truncated cone shape. The results show that the plug body of the latter shape possesses much larger bearing capacity, namely 4.48 times at elastic deformation stage and 4.54 times at failure stage compared to the former shape. Numerical simulation is then conducted to understand the mechanical and structural responses of plug body and surrounding rock mass. The mechanical parameters of the surrounding rock mass are firstly back-analyzed based on the monitoring data. The calculation laws of deformation and equivalent plastic strain show that the numerical simulation results are rational and provide subsequent mechanism analysis with an established basis. Afterwards, the bearing mechanism of TTA is studied. It is concluded that the plug body of circular truncated cone shape is able to take advantage of the material strength of the surrounding rock mass, which greatly enhances its bearing capacity. The ultimate bearing capacity of TTA, therefore, is concluded to be determined by the material strength of surrounding rock mass. Finally, recommendations for TTA design are proposed and discussed.

• 한국구조물진단유지관리공학회 논문집
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• 제12권2호
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• pp.171-180
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• 2008

본 논문의 목적은 채널형 단부정착장치를 사용하여 CFRP판으로 보강한 철근콘크리트 보의 구조적 거동을 평가하는 것이다. 총 12개의 시험체를 제작하였으며, 이 중에는 보강판의 효율성을 높이기 위해 채널형 단부정착장치를 사용한 시험체와 사용하지 않은 시험체가 있다. 모든 시험체의 단면 크기는 동일하며, 주철근량과 콘크리트의 강도를 변화시켰다. 하중재하는 모든 시험체에서 4점 휨시험으로 진행되었으며, 각 재료의 변형률, 균열, 하중, 및 파괴모드가 시험 중에 측정되었다. 모든 시험체의 시험결과는 변형, 강도, 그리고 파괴모드 측면으로 분석되었다. 실험결과에 대한 분석를 통해서 채널형 단부정착장치를 사용한 RC보는 그 파괴모드가 급작스런 부착파괴에서 변형이나 강도적 측면에서 구조적 성능이 매우 향상된 연성적 파괴모드로 전환되는 것을 확인할 수 있었다.

• Earthquakes and Structures
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• 제5권5호
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• pp.527-552
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• 2013

Development of flexural yielding and large rotation ductilities in the plastic hinge zones of frame members is synonymous with the spread of bar reinforcement yielding into the supporting anchorage. Yield penetration where it occurs, destroys interfacial bond between bar and concrete and reduces the strain development capacity of the reinforcement. This affects the plastic rotation capacity of the member by increasing the contribution of bar pullout. A side effect is increased strains in the compression zone within the plastic hinge region, which may be critical in displacement-based detailing procedures that are linked to concrete strains (e.g. in structural walls). To quantify the effects of yield penetration from first principles, closed form solutions of the field equations of bond over the anchorage are derived, considering bond plastification, cover debonding after bar yielding and spread of inelasticity in the anchorage. Strain development capacity is shown to be a totally different entity from stress development capacity and, in the framework of performance based design, bar slip and the length of debonding are calculated as functions of the bar strain at the loaded-end, to be used in calculations of pullout rotation at monolithic member connections. Analytical results are explored parametrically to lead to design charts for practical use of the paper's findings but also to identify the implications of the phenomena studied on the detailing requirements in the plastic hinge regions of flexural members including post-earthquake retrofits.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume II
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• pp.582-585
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• 2006

Augustine volcano is an active stratovolcano located southwest of Anchorage, Alaska. Augustine volcano experienced seven significantly explosive eruptions in 1812, 1883, 1908, 1935, 1963, 1976, and 1986, and a minor eruption in January 2006. To measure ground surface deformation of Augustine volcano, we applied satellite radar interferometry with ERS-1/2 and ENVISAT SAR images acquired from three descending and three ascending satellite tracks. Multiple interferograms are stacked to reduce artifacts due to changes in atmospheric condition and retrieve temporal deformation sequence. For this, we used Least Square (LS) method for reducing atmospheric effects and Singular Value Decomposition (SVD) method for the retrieval of a temporal deformation sequence. Interferograms before 2006 eruption show about 3 cm/year subsidence by contraction of pyroclastic flow deposits from the 1986 eruption. Interferograms during 2006 eruption do not show significant deformation around volcano crater. Interferograms after 2006 eruption show again a several cm subsidence by compaction and contraction of pyroclastic flow deposits for a few months. This study demonstrates that satellite radar interferometry can monitor deformation of Augustine volcano to help understand the magma plumbing system driving surface deformation.

• Steel and Composite Structures
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• 제17권6호
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• pp.791-801
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• 2014

The effects of anchor on fractured specimens in splitting test are simulated by DDARF method, the results of which are compared with laboratory test results. They agree well with each other. The paper contents also use the laboratory model test. The main research objects are three kinds of specimens, namely intact specimens, jointed specimens and anchored-jointed specimens. The results showed that with the joint angle increased, the weakening effects of jointed rock mass are more obvious. At these points, the rock bolts' strengthening effects on the specimens have become more significant. There is a significant impact on the failure modes of rock mass by the joint and the anchorage.

• 한국지진공학회논문집
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• 제3권3호
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• pp.33-44
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• 1999

지진의 시간적인 요인, 즉 반복하중효과와 이에 따른 누적소성변위를 고려하기 위하여 에너지 평형에 근거한 해석방법이 개발되었다 본 논문에서는 내진 설계되지 않은 골조 기둥의 파괴유형에 주목하고자 한다. 이를 위하여 기둥의 휨강도저감모델이 제안되는데 파괴유형별로는 콘크리트에의한 파괴 주근의 부착/정착강도 파괴 및 저사이클피로에 의한 주근의 파단등을 고려하였다 에너지에 근거한 모델에 의하여 예측된 응답과 실험결과를 비교하였으며 이론과 실험간의 응답과 파괴유형이 서로 매우 가까움을 확인하였다.

• 대한토목학회논문집
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• 제41권1호
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• pp.1-11
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• 2021

기존 육상풍력터빈의 리파워링 시 기존 기초를 재사용하기 위해서는 증가된 타워 직경 및 터빈 하중에 맞게 기존 기초를 재설계 및 보강하는 것이 중요하다. 본 연구에서는 육상풍력터빈의 기초형식 중 가장 널리 사용되고 있는 확대기초의 재사용을 위해 기존 확대기초 위에 새로운 콘크리트 기초부를 증설하는 슬래브 확장 보강방법 및 앵커부 구조디테일에 대해 검토하였다. 그리고 앵커부 구조디테일에 따른 보강된 확대기초의 하중저항성능을 실험적으로 평가하였다. 실험결과, (1) 앵커부 철근 유무에 따라 내력이 30 % 이상 증가하였다. (2) 앵커링에 부착된 Pile-sleeve는 앵커링과 콘크리트 사이의 전단슬립거동을 방지하여 회전강성 증가에 기여하였다. (3) Slab connector는 신?구 콘크리트 분리 방지 및 일체화 거동을 향상시켜 내력 및 변형능력 증가에 기여하였다.

• Advances in concrete construction
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• 제1권1호
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• pp.103-119
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• 2013

The applicability of limit analysis methods in design and assessment of concrete structures generally requires a certain plastic deformation capacity. The latter is primarily provided by the ductility of the reinforcement, being additionally affected by the bond properties between reinforcing steel and concrete since they provoke strain localization in the reinforcement at cracks. The bond strength of reinforcing bars is not only governed by concrete quality, but also by construction details such as bar ribbing, bar spacing or concrete cover thickness. For new concrete structures, a potentially unfavorable impact on bond strength can easily be anticipated through appropriate code rules on construction details. In existing structures, these requirements may not be necessarily satisfied, consequently requiring additional considerations. This two-part paper investigates in a theoretical study the impacts of the most frequently encountered construction details which may not satisfy design code requirements on bond strength, steel strain localization and plastic deformation capacity of cracked structural concrete. The first part introduces basic considerations on bond, strain localization and plastic deformation capacity as well as the fundamentals of the Tension Chord Model underlying the further investigations. It also analyzes the impacts of the hardening behavior of reinforcing steel and concrete quality. The second part discusses the impacts of construction details (bar ribbing, bar spacing, and concrete cover thickness) and of additional structure-specific features such as bar diameter and crack spacing.