• Structural Engineering and Mechanics
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• 제68권2호
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• pp.193-201
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• 2018

This paper describes an experimental study on the seismic performance of steel reinforced concrete (SRC) T-shaped columns. The lateral loads were applied along the web of the column with different loading histories, such as monotonic loading, mixed loading of variable amplitude cyclic loading and monotonic loading, constant amplitude cyclic loading and variable amplitude cyclic loading. The failure modes, load-displacement curves, characteristic loads and displacements, ductility, strength and stiffness degradations and energy dissipation capacity of the column were analyzed. The effects of loading history on the seismic performance were focused on. The test results show that the specimens behaved differently in the aspects of the failure mode subject to different loading history, although all the failure modes can be summarized as flexural failure. The hysteretic loops of specimens are plump, and minimum values of the failure drift angles and ductility coefficients are 1/24 and 4.64, respectively, which reflect good seismic performance of SRC T-shaped column. With the increasing numbers of loading cycles, the column reveals lower bearing capacity and ductility. The strength and stiffness of the column with variable amplitude cyclic loading degrades more rapidly than that with constant amplitude cyclic loading, and the total cumulative dissipated energy of the former is less.

• Earthquakes and Structures
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• 제14권3호
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• pp.187-201
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• 2018

The paper describes a modified cyclic bar model including bond-slip phenomena between steel reinforcing bars and surrounding concrete. The model is focused on plain bar and is useful, for its simplicity, for the seismic analyses of RC structures with plain bars and insufficient constructive details, such as in the case of '60s -'70s Mediterranean buildings. The model is based on an imposed exponential displacements field along the bar including both steel deformation and slip; through the adoption of equilibrium and compatibility equations a stress-slip law can be deducted and simply applied, with opportune operations, to RC numerical models. This study aims to update and complete the original monotonic model published by the authors, solving some numerical inconsistencies and, mostly, introducing the cyclic formulation. The first aim is achieved replacing the imposed linear displacement field along the bar with an exponential too, while the cyclic behaviour is described through a formulation based on the results of parametric analyses concerning a large range of steel and concrete properties and geometric configurations. Validations of the proposed model with experimental results available in the current literature confirm its accuracy and the reduced computational burden, highlighting its suitability in performing nonlinear analyses of RC structures.

• 복합신소재구조학회 논문집
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• 제4권1호
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• pp.33-39
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• 2013

Structural insulated panels, structurally performed panels consisting of a plastic insulation bonded between two structural panel facings, are one of emerging products with a viewpoint of its energy and construction efficiencies. These components are applicable to fabricated wood structures. In Korea, there are few technical documents regulated structural performance and engineering criteria in domestic market. This study was conducted to identify fundamental performance of both monotonic load and quasi static cyclic load for SIPs in shear wall application. Static test results showed that maximum load was 44.3kN, allowable shear load was 6.1kN/m, shear stiffness was 1.23 M N/m, and ductility ratio was 3.6. Cyclic test was conducted by two kinds of specimens : single panel and double panels. Cyclic test results, which were equivalent to static test results, showed that maximum load was 45.42kN, allowable shear load was 6.3kN/m. Furthermore the accumulated energy dissipation capability for double panels was as 2.3 times as that for single panel. From performance of structural tests, it was recommended that the allowable shear load for panels was at least 6.1kN/m.

• 한국공간구조학회논문집
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• 제23권2호
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• pp.53-60
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• 2023

Recently, a novel cast-in specialty insert was developed in Korea as an anchor for lightweight pipe supports, including fire-protection pipes. As these pipe supports and anchors play a critical role in transferring loads of fire-protection pipes to structural members, it is crucial to evaluate their seismic performance before applying the newly developed insert. In this study, the seismic shear performance of the insert anchors was evaluated through cyclic loading tests based on the loading protocols of ACI 355.2 and FEMA 461. Initially, five monotonic loading tests were conducted on the insert anchors in cracked concrete, followed by cyclic loading tests based on the monotonic test results. The findings revealed that the insert anchors exhibited negligible decrease in shear strength even after cyclic loading. Furthermore, a comparison of the maximum load and displacement of the insert anchors obtained under the loading protocols of ACI 355.2 and FEMA 461 was performed to investigate the applicability of the FEMA 461 loading protocol for anchor performance evaluation.

• 한국지반신소재학회논문집
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• 제8권2호
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• pp.47-54
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• 2009

국내 대부분을 차지하고 있는 자갈 도상궤도는 지속적인 열차반복하중에 의해 마모, 노반으로 관입, 노반표면의 불균질 등에 의해 도상자갈의 기능을 상실하게 된다. 이러한 현상이 지속적으로 발생하면 설계 당초 주요 기능이었던 배수기능을 충분히 발휘하지 못하기 때문에 강우가 노반에 체류되고 물로 인해 간극수압이 증가하여 전단강도가 저하되어 점진적으로 노반이 연약화된다. 이 논문에서는 원형모형실험을 이용하여 부직포 3종류에 대하여 0일, 3일, 7일 체수조건으로 하여 반복하중을 재하시킴으로써 부직포의 침하특성과 지지력 변화를 관찰하였다. 실험결과 0일 체수조건에서 토목섬유 보강과 무보강에 따라 최종 변위는 약 1% 차이가 있으며, 지반의 포화도가 증가함에 따라 침하량이 커지는 경향이 있었다. 보강재의 중량이 클수록 소성침하량이 작게 평가되었으며, 임계 함수비를 초과한 경우에는 부직포의 인장강도와 중량에 따라 침하량의 차이가 발생하였다. 또한 무보강과 비교해 볼 때 부직포에 의한 토압 저감효과는 있으나, 부직포의 중량에 의한 토압저감 효과는 영향이 미미한 것으로 평가되었다.

• 한국지진공학회논문집
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• 제10권3호
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• pp.47-55
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• 2006

본 연구는 도로교의 교각으로 널리 사용되고 있는 2주형 철근 콘크리트 교각의 내진성능과 보강방안을 실험적으로 수행하였다. 실험체는 지름 400mm, 높이 2,000mm인 2주형 원형교각 10기를 제작하였으며, 하중은 $0.1f_{ck}A_g$ 크기의 축방향하중하에서 교축방향과 교축직각방향의 이축 횡방향하중을 교번 반복재하하였다. 실험변수는 심부구속철근비, 주하중방향, 주철근 겹침이음 그리고 보강방안을 선택하였다. 주철근 겹침이음이 있는 교각에 대한 보강방안으로 steel band, steel jacket, 그리고 prestress 강선을 이용하였다. 실험 결과 주하중방향이 교축직각인 실험체가 소성힌지구간이 교각의 상 하부 양측에 발생하면서 주하중 방향이 교축방향인 실험체보다 연성 능력이 우수한 것으로 나타났다. 프리스트레스 강선으로 보강한 실험체는 과보강으로 인한 소성힌지구간의 이동으로 연성도 저하가 나타났으나, steel jacket 및 steel band로 보강한 실험체는 모두 요구연성도를 만족하는 것으로 나타났다. 특히, steel band에 의한 보강방안은 시공성 등을 감안하여 바람직한 철근 콘크리트 교각의 내진 보강방안으로 고려될 수 있다.

• Steel and Composite Structures
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• 제18권6호
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• pp.1569-1582
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• 2015

This study explores the lateral deflections of diagonal braces in concentrically-braced earthquake-resisting frames. The performance of this widely-used system is often compromised by the flexural buckling of slender braces in compression. In addition to reducing the compressive resistance, buckling may also cause these members to undergo sizeable lateral deflections which could damage surrounding structural components. Different approaches have been used in the past to predict the mid-length lateral deflections of cyclically loaded steel braces based on their theoretical deformed geometry or by using experimental data. Expressions have been proposed relating the mid-length lateral deflection to the axial displacement ductility of the member. Recent experiments were conducted on hollow and concrete-filled circular hollow section (CHS) braces of different lengths under cyclic loading. Very slender, concrete-filled tubular braces exhibited a highly ductile response, undergoing large axial displacements prior to failure. The presence of concrete infill did not influence the magnitude of lateral deflection in relation to the axial displacement, but did increase the number of cycles endured and the maximum axial displacement achieved. The corresponding lateral deflections exceeded the deflections observed in the majority of the previous experiments that were considered. Consequently, predictive expressions from previous research did not accurately predict the mid-height lateral deflections of these CHS members. Mid-length lateral deflections were found to be influenced by the member non-dimensional slenderness (${\bar{\lambda}}$) and hence a new expression was proposed for the lateral deflection in terms of member slenderness and axial displacement ductility.

• 한국지진공학회논문집
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• 제7권4호
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• pp.51-61
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• 2003

본 연구는 철근콘크리트 교각에 대한 새로운 내진설계법을 개발하기 위한 연구의 일환으로서, 축력과 함께 반복 횡하증을 받는 철근콘크리트 교각의 곡률연성도와 변위연성도의 상관관계를 분석하고 연성도 상관관계식을 제시함을 목적으로 한다. 이를 위하여, 반복하중을 받는 철근콘크리트 기둥의 횡하중-변위 포락곡선 실험결과를 비교적 정확하게 예측하며, 특히 변형능력 및 연성도에 대하여는 실험결과에 비하여 안전측의 결과를 제공하는 비선형해석 프로그램(NARCC)를 이용하였다. 해석의 대상 교각으로는, 단면지름, 형상비, 콘크리트 강도, 축방향철근 항복강도, 심부구속철근 항복강도, 축방향철근비, 축력비, 심부구속철근비 등을 주요변수로 하여, 총 7,200개의 철근콘크리트 나선철근 기둥 모델을 채택하였으며, 세 가지 항복변위의 기준을 적용하여 총 21,600개의 해석결과자료를 대상으로 상관관계를 분석하여 형상비를 주요변수로 한 곡률연성도와 변위연성도의 상관관계식을 제안하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.99-104
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• 2002

This paper presents an analytical prediction of the fatigue damage of reinforced concrete bridge columns subjected to cyclic load. Material nonlinearity is taken into account by comprising tensile, compressive and shear models of cracked concrete and a model of reinforcing steel. The smeared crack approach is incorporated. In boundary plane at which each member with different thickness is connected, local discontinuity in deformation due to the abrupt change in their stiffness can be taken into account by introducing interface element. The effect of number of load reversals with the same displacement amplitude has been also taken into account to model the reinforcing steel and concrete. The proposed numerical method for fatigue damage of reinforced concrete bridge columns subjected to cyclic load is verified by comparison with reliable experimental results.

• Computers and Concrete
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• 제13권3호
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• pp.377-387
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• 2014

This paper presents an experimental study on socket base connections of precast reinforced concrete columns. The main purpose of this study is to determine socket base connection which has the closest behavior to monolithic casted column-base joints. For this purpose, six specimens having different column-socket base connection details were tested under cyclic loading. For each test, strength, stiffness, ductility and drift ratios of the specimens were determined. Test results indicated that a suggested connection type is 10%-30% stronger than the other type of connections under lateral loading. The welded connection (PC-5) had better lateral load carrying capacity and ductility. On the other hand, performance of standard connection (PC-1) which is commonly used in construction was weaker than other connections. Thus, decision of connection type should be referred not only performance but also applicability.