• 산업기술연구
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• 제25권A호
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• pp.67-73
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• 2005

In this research, centrifuge model experiments and numerical approach of finite element method to analyze experimental results were performed to investigate the behavior of improved ground with sand compaction piles. One of typical clay minerals, kaolinite powder, were prepared for soft ground in model tests. Jumunjin standard sand was used to sand compaction pile installed in the soft soil. In order to investigate the characteristics of mechanical behavior of sand compaction piles with low replacement ratios, centrifuge model experiments with the replacement ratio of 40%, changing the width of improved area with respect to testing results the width of surcharge loads, were carried out to obtain of bearing capacity, characteristics of load-settlement, vertical stresses acting on the sand pile and the soft soil failure mechanism in improved ground.

• Steel and Composite Structures
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• 제42권2호
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• pp.265-275
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• 2022

A new type of precast steel reinforced concrete (PSRC) column was put forward in this paper. In order to study the static performance of PSRC column and hollow precast steel reinforced concrete (HPSRC) column subjected to combined compression and shear loading, a parametric test was carried out and effects of axial compression ratio, concrete strength and shear ratio on the mechanical behavior of composite PSRC column and HPSRC column were explored. In addition, the cracks development, load-span displacement relationship, strain distribution and shear bearing strength of column specimens were emphatically focused. Test results implied that shear failure of all specimens occurred during the test, and higher strength of cast-in-place concrete, smaller shear ratio and larger axial compression ratio could lead to greater shear resistance, but when the axial compression ratio was larger than 0.36, the shear capacity began to decrease gradually. Furthermore, truss-arch model for determining the shear strength of PSRC column and HPSRC column was proposed and the calculated results obtained from proposed method were verified to be valid.

• Steel and Composite Structures
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• 제47권2호
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• pp.217-238
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• 2023

In this study, a parametric study was performed considering material properties of concrete, material properties of steel, the number of longitudinal reinforcement (reinforcement ratio), CFRP ply orientations, a number of layers as variables by using ABAQUS. Firstly, the parameters used in the Hashin failure criteria were verified using four coupon tests of CFRP. Secondly, the numerical models of the beams strengthened by CFRP were verified using five experimental data. Finally, eighty numerical models and eighty analytic calculations were developed to investigate the effects of the aforementioned variables. The results revealed that in the case of using fibrous polymer to prevent shear failure, the variables related to reinforced concrete significantly affected the behavior of specimens, whereas the variables related to CFRP composite have a slight effect on the behavior of the specimens. As a result of numerical analysis, while the increase in the longitudinal tensile and compression reinforcement, load bearing capacity increases between 23.6%-70.7% and 5.6%-12.2%, respectively. Increase in compressive strength (29 MPa to 35 MPa) leads to a slight increase in the load-carrying capacity of the specimens between 4.6% and 7.2%. However, the decrease in the compressive strength (29 MPa to 20 MPa) significantly affected (between 6.4% and 8.1% decrease observed) the behavior of the specimens. As the yield strength increases or decreases, the capacity of specimens increase approximately 27.1% or decrease 12.1%. The effects of CFRP ply orientation results have been obtained as a negligible well approximately 3.7% difference. An increasing number of CFRP layers leads to almost no effect (approximately 2.8%) on the behavior of the specimen. Finally, according to the numerical analysis, the ductility values obtained between 4.0 and 6.9 indicate that the beams have sufficient ductility capacity.

• 한국전산구조공학회논문집
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• 제21권2호
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• pp.145-151
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• 2008

지금까지의 지진 관련 연구는 주로 교량 받침 자체의 성능개선이 주요 관심 과제였으나, 본 논문에서는 받침 종류에 따라 교량에 미치는 전반적인 지진거동 특성을 분석하고 교량 공사비에 미치는 영향을 검토하였다. 이를 위해 실무에서 많이 적용되는 PSC I형 교량에 대해 교량받침의 종류를 변화시키며 교각 높이를 매개변수로 하여 상시 및 지진해석을 수행하였다. 특히 지진해석을 통해 산출한 단면력을 고려하여 PSC I형 교량받침의 변위, 지진하중에 의한 교각 기둥의 직경, 상부여유 간격 등의 변화를 분석하였다. 고교각인 경우 탄성받침보다는 지진격리장치를 적용하는 것이 지진에 의한 상부구조의 이동량을 줄여 신축이음장치의 규격을 줄일 수 있으므로 차량의 주행성 및 교량의 유지관리 측면에서 바람직 할 것으로 판단되었고, 교량 하부 구조 단면이 축소되어 미관개선 및 경제성 개선의 효과가 있는 것으로 분석되었다. 결국, PSC I형 교량받침 설계시 일률적으로 탄성받침을 적용하는 것보다 정밀한 내진해석을 통해 지진격리장치를 적용하는 것이 구조적정성 측면 및 공사비 측면에서 타당하다는 결론에 도달하였다.

• 대한토목학회논문집
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• 제35권4호
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• pp.863-874
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• 2015

본 연구에서는 보강날개로 보강된 수중잠제 지지말뚝의 보강효과를 분석하기 위하여 하중전이거동을 분석하였다. 먼저 3차원 유한요소해석을 통해 말뚝의 변위 및 하중전이곡선(지반반력) 결과로부터 보강효과를 확인하고, 하중전이곡선에서 극한저항력 비율로 보강말뚝의 수평 및 인발하중에 대한 보강계수를 산정함으로써 보강효과를 정량화 하였다. 산정된 보강계수를 쌍곡선 하중전이함수의 극한저항력 $p_u$와 $t_{max}$에 곱해서 보정상수(fitting parameter)로 적용하여 보강효과를 고려한 하중전이함수를 제안하였다. 제안된 하중전이함수가 수치해석 결과를 잘 반영하고 있는지 확인하기 위해 3차원 유한요소해석을 비교하여 보강말뚝의 하중전이거동을 분석하였다. 제안된 하중전이함수를 하중전이법 해석에 적용하여, 실제 수중잠제를 해석한 결과 보강말뚝의 전단력, 휨 모멘트, 변위가 무보강말뚝보다 작게 발생하고, 지반반력은 더 크게 발생하여 비교적 경제적인 설계가 가능할 것으로 판단된다.

• 한국지반공학회논문집
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• 제24권11호
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• pp.61-70
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• 2008

본 연구에서는 국내 4개 지역에서 시공된 총 10본의 대구경 암반 근입 현장타설말뚝의 양방향 말뚝 선단재하시험과 일반적인 말뚝두부 재하시험을 토대로 하중 재하방식에 따른 말뚝의 침하거동 및 하중전이 거동 특성을 분석하였다. 이로부터 양방향 재하하중을 받는 현장타설말뚝의 등가 말뚝 두부하중침하 거동을 고찰하곤 기존 등가 두부하중침하 곡선 산정방법과의 비교분석을 통하여 주면하중에 의해 추가적인 선단침하량의 영향정도를 분석하였다. 본 연구결과, 주면하중에 의해 발생되는 선단침하량을 고려한 하중전이해석(coupled load transfer analysis)을 통한 하중-침하량 예측값은 정재하 시험결과를 적절히 예측하는 것으로 나타났으나, 근사적 해석법을 통한 등가 하중-침하 곡선 및 일반적인 하중전이해식(uncoupled load transfer analysis)의 예측값은 정재하 시험결과에 비해 침하량을 과소 평가할 수 있음을 알 수 있었다. 하지만, 시험말뚝 근입부분의 암반층이 매우 단단할 경우 주면하중에 의한 선단침하량이 매우 작은 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제47권4호
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• pp.575-598
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• 2013

The study presents the results of an experimental program concerning the shear force transfer between reinforced concrete (RC) jackets and existing columns with damages. In order to investigate the effectiveness of the repair method applied and the contribution of each shear transfer mechanism of the interface. It includes 22 concrete columns (core) (of 24,37MPa concrete strength) with square section (150mm side, 500 mm height and scale 1:2). Ten columns had initial construction damages and twelve were subjected to initial axial load. Sixteen columns have full jacketing at all four faces with 80mm thickness (of 31,7MPa concrete strength) and contain longitudinal bars (of 500MPa nominal strength) and closed stirrups spaced at 25mm, 50mm or 100mm (of 220MPa nominal strength). Fourteen of them contain dowels at the interface between old and new concrete. All columns were subjected to repeated (pseudo-seismic) axial compression with increasing deformation cycles up to failure with or without jacketing. Two load patterns were selected to examine the difference of the behavior of columns. The effects of the initial damages, of the reinforcement of the interface (dowels) and of the confinement generated by the stirrups are investigated through axial- deformation (slip) diagrams and the energy absorbed diagrams. The results indicate that the initial damages affect the total behavior of the column and the capacity of the interface to shear mechanisms and to slip: a) the maximum bearing load of old column is decreased affecting at the same time the loading capacity of the jacketed element, b) suitable repair of initially damaged specimens increases the capacity of the jacketed column to transfer load through the interface.

• 한국지반공학회논문집
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• 제28권11호
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• pp.33-40
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• 2012

말뚝과 raft의 하중 분담 효과를 고려한 Piled Raft 기초의 설계는, 말뚝의 지지력만을 고려하여 설계하는 기존의 말뚝기초 설계 방식에 비해 경제적인 설계를 가능하게 해준다. 일반적으로 Piled Raft 기초 거동의 해석 및 설계는, 해석의 복잡성으로 인해 주로 컴퓨터를 이용한 수치 해석을 이용하고 있으며, 하중 분담 효과에 대한 해석 또한 개별적 상황에 따른 수치해석의 결과로 이루어진다. 본 연구에서는 기초 요소의 하중-침하 특성을 고려하여 Piled Raft 기초에서의 수직하중에 대한 raft와 말뚝의 하중 분담 효과를 평가할 수 있는 모델을 제안하고자 하였다. 기초의 비선형적 거동을 고려하여 말뚝과 raft의 거동을 각각 쌍곡선(hyperbolic curve) 형태의 정규화된 하중-침하 곡선(normalized load-settlement curve)으로 표현하고, 이를 통해 기초의 침하에 따른 말뚝과 raft의 하중 분담 정도를 평가할 수 있는 모델을 제시하였다. 또한 제시한 모델의 적용성을 평가하기 위하여 Piled Raft 기초에 대한 원심모형실험 결과와 비교하였다. 그 결과, 제시한 모델과 원심모형실험 결과로부터 나타난 침하에 따른 하중 분담률의 변화 양상이 전체적으로 유사한 형태를 보였다.

• Computers and Concrete
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• 제16권1호
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• pp.141-161
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• 2015

A significant portion of residential areas of Turkey is located in active earthquake zones. In Turkey occurred major earthquakes in last twenty years, such as Erzincan (1992), Kocaeli and $D{\ddot{u}}zce$ (1999), $Bing{\ddot{o}}l$ (2003), Van (2011). These earthquakes have demonstrated that reinforced concrete (RC) buildings having horizontal and vertical irregularities are significantly damaged, which in turn most of them are collapsed. Architectural design and arrangement of load-bearing system have important effect on RC building since architectural design criteria in design process provide opportunity to make this type of buildings safer and economical under earthquake loads. This study aims to investigate comparatively the effects of weak story irregularity on earthquake behavior and rough construction costs of RC buildings by considering different soil-conditions given in the Turkish Earthquake Code. With this aim, Sta4-CAD program based on matrix displacement method is utilized. Considering that different story height and compressive strength of concrete, and infill walls or their locations are the variables, a set of structural models are developed to determine the effect of them on earthquake behavior and rough construction costs of RC buildings. In conclusion, some recommendations and results related to making RC buildings safer and more economical are presented by comparing results obtained from structural analyses.

• Geomechanics and Engineering
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• 제7권2호
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• pp.165-181
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• 2014

In the past decade, different types of underreamed ground anchors have been developed for substructures requiring uplift resistance. This article introduces a new type of umbrella-shaped anchor. The uplift behavior of this ground anchor in clay is studied through a series of laboratory and field uplift tests. The test results show that the umbrella-shaped anchor has higher uplift capacity than conventional anchors. The failure mode of the umbrella-shaped anchor in a large embedment depth can be characterized by an arc failure surface and the dimension of the plastic zone depends on the anchor diameter. The anchor diameter and embedment depth have significant influence on the uplift behavior. A finite element model is established to simulate the pullout of the ground anchor. A parametric study using this model is conducted to study the effects of the elastic modulus, cohesion, and friction angle of soils on the load-displacement relationship of the ground anchor. It is found that the larger the elastic modulus and the shear strength parameters, the higher the uplift capacity of the ground anchor. It is suggested that in engineering design, the soil with stiffer modulus and higher shear strength should be selected as the bearing stratum of this type of anchor.