• Structural Engineering and Mechanics
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• 제15권4호
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• pp.477-493
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• 2003

Masonry is not a simple material, the influence of mortar joints as a plane of weakness is a significant feature and this makes the numerical modelling of masonry very difficult especially when dynamic (seismic) analysis is involved. In order to develop a simple numerical model for masonry under earthquake load, an analytical model based on Distinct Element Method (DEM) is being developed. At the first stage, the model is applied to simulate the in-plane shear behaviour of an unreinforced masonry wall with and without opening where the testing results are available for comparison. In DEM, a solid is represented as an assembly of discrete blocks. Joints are modelled as interface between distinct bodies. It is a dynamic process and specially designed to model the behaviour of discontinuities. The numerical solutions obtained from the distinct element analysis are validated by comparing the results with those obtained from existing experiments and finite element modelling.

• Steel and Composite Structures
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• 제18권3호
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• pp.711-737
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• 2015

Steel Plate Shear Walls (SPSWs) have been accepted widely as an effective lateral load resisting system. For seismic performance evaluation of a multi-story building with SPSWs, detailed finite element models or a strip model can be used to represent the SPSW components. However, such models often require significant effort for tall or medium height buildings. In order to simplify the analysis process, discrete elements for the framing members can be used. This paper presents development of a simplified equivalent braced model to study the behavior of the SPSWs. The proposed model is expected to facilitate a simplification to the structural modeling of large buildings with SPSWs in order to evaluate the seismic performance using regular structural analysis tools. It is observed that the proposed model can capture the global behavior of the structures quite accurately and potentially aid in the performance-based seismic design of SPSW buildings.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.469-475
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• 2004

The transient analysis of delaminated smart composite laminates is studied using an improved layerwise laminate theory. The theory is capable of capturing interlaminar shear stresses that are critical to delamination. The presence of discrete delamination is modeled through the use of Heaviside unit step functions. Stress free boundary conditions are enforced at all fee surfaces. Continuity in displacement field and transverse shear stresses are enforced at each ply level. In modeling piezoelectric composite plates, a coupled piezoelectric-mechanical formulation is used in the development of the constitutive equations. Numerical analysis is conducted to investigate the effect of nonlinearity in the transient vibration of bimodular behavior caused by the contact impact of delaminated interfaces. Composite plates with delamination, subject to external loads and voltage history from surface bonded sensors, are investigated and the results are compared with corresponding experimental results and plates without delamination.

• Geomechanics and Engineering
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• 제12권4호
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• pp.639-655
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• 2017

The binary mixture consists of two types of granular media with different physical attributes and sizes, which can be characterized by the percentage of large granules by weight (P) and the particle size ratio (${\alpha}$). Researchers determine that two thresholds ($P_S$ and $P_L$) exist for the peak shear strength of binary mixtures, i.e., at $P{\leq}P_S$, the peak shear strength is controlled by the small granules; at $P{\leq}P_L$, the peak shear strength is controlled by the large granules; at $P_S{\leq}P{\leq}P_L$, the peak shear strength is governed by both the large and small granules. However, the thresholds of binary mixtures with different ${\alpha}$ values, and the explanation related to the inner details of binary mixtures to account for why these thresholds exist, require further confirmation. This paper considers the mechanical behavior of binary mixtures with DEM analysis. The thresholds of binary mixtures are found to be strongly related to their coordination numbers $Z_L$ for all values of ${\alpha}$, where $Z_L$ denotes the partial coordination number only between the large particles. The arrangement structure of the large particles is examined when P approaches the thresholds, and a similar arrangement structure of large particles is formed in both 2D and 3D particle systems.

• Geomechanics and Engineering
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• 제24권5호
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• pp.443-456
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• 2021

Structural design of the vertical displacements and shear strains in the earth fill (EF) dams has great importance in the structural engineering problems. Moreover, far fault earthquakes have significant seismic effects on seismic damage performance of EF dams like the near fault earthquakes. For this reason, three dimensional (3D) earthquake damage performance of Oroville dam is assessed considering different far-fault ground motions in this study. Oroville Dam was built in United States of America-California and its height is 234.7 m (770 ft.). 3D model of Oroville dam is modelled using FLAC3D software based on finite difference approach. In order to represent interaction condition between discrete surfaces, special interface elements are used between dam body and foundation. Non-reflecting seismic boundary conditions (free field and quiet) are defined to the main surfaces of the dam for the nonlinear seismic analyses. 6 different far-fault ground motions are taken into account for the full reservoir condition of Oroville dam. According to nonlinear seismic analysis results, the effects of far-fault ground motions on the nonlinear seismic settlement and shear strain behaviour of Oroville EF dam are determined and evaluated in detail. It is clearly seen that far-fault earthquakes have very significant seismic effects on the settlement-shear strain behaviour of EF dams and these earthquakes create vital important seismic damages on the swelling behaviour of dam body surface. Moreover, it is proposed that far-fault ground motions should not be ignored while modelling EF dams.

• 한국지반공학회논문집
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• 제25권2호
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• pp.17-24
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• 2009

일반적으로 점토의 비 배수전단강도 산정은 실내실험을 통해 구하지만 초연약점토의 경우 재료의 특성 상 실내실험이 어렵고, 현장실험 또한 여러 제약조건들을 감수해야 한다. 따라서 본 논문에서는 실내에서 수행한 물성실험 및 슬럼프실험과 실내 베인 전단실험의 결과를 회귀분석을 통해 슬럼프 값과 비 배수전단강도 사이의 상관 관계식을 도출하였다. 도출된 상관 관계식의 신뢰성 확보를 위하여 t-분포를 이용한 통계분석을 실시하였고 현장의 데이터와 비교 분석하여 관계식의 적용성 및 신뢰성을 확보하였다.

• 한국지반공학회논문집
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• 제23권8호
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• pp.59-68
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• 2007

사질토의 직교 이방 탄성계수를 실험적 방법과 개별 요소법을 이용하여 측정하고 결과를 정량적으로 비교-분석하였다. 실내 시험에서는 미소 응력 제어 반복재하시험과 벤더 엘리먼트의 측정 결과를 조합하여 탄성 특성을 구하였으며, 개별 요소법에서는 실내 시험 방법과 상응하는 반복재하시험을 모사하였다. 축 방향 및 전단방향에 관련된 탄성 특성의 비교 결과는 제한된 조건에서도 개별 요소법이 복잡한 실내 시험 과정을 모사할 수 있음을 보여주었다. 방사 방향 재하시험 결과에서 나타난 두 방법 간 차이의 비교 분석 결과는 개별 요소법이 실내 시험으로 구한 개별 측정치의 정량적 타당성을 확인하는데 충분히 활용될 수 있음을 보여준다.

• 터널과지하공간
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• 제25권4호
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• pp.359-372
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• 2015

암반에는 단층, 절리, 층리 등의 불연속면이 많이 포함되어 있다. 이러한 불연속면은 기하학적 복합성에 의해 복잡한 구조로 나타난다. 이 연구는 스텝으로 배열된 두 전단균열의 끝에서 나타나는 구조 발달을 수치해석적으로 연구하였다. 이 연구에서는 PFC2D(Particle Flow Code) 프로그램을 이용하여 두 전단균열의 끝에서 형성되는 초기균열(incipient fracture)뿐만 아니라 초기균열에서 덧자라는 균열의 성장과정을 살펴보았으며, 균열 발생 시 나타나는 주변응력상태를 관찰하였다. 모든 실험 결과에서는 균열 끝에서 발생한 초기 균열 대부분이 인장균열에 의한 것으로 나타났으며, 균열의 전파각은 초기에 $30{\sim}57^{\circ}$에서 실험이 더 진행되면 저각으로 발달하는 것으로 나타났다.

• Steel and Composite Structures
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• 제19권6호
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• pp.1403-1419
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• 2015

When precast concrete infill panels are connected to steel frames at discrete locations, interaction at the structural interface is neither complete nor absent. The contribution of precast concrete infill panels to the lateral stiffness and strength of steel frames can be significant depending on the quality, quantity and location of the discrete interface connections. This paper presents preliminary experimental and finite element results of an investigation into the composite behaviour of a square steel frame with a precast concrete infill panel subject to lateral loading. The panel is connected at the corners to the ends of the top and bottom beams. The Frame-to-Panel-Connection, FPC4 between steel beam and concrete panel consists of two parts. A T-section with five achor bars welded to the top of the flange is cast in at the panel corner at a forty five degree angle. The triangularly shaped web of the T-section is reinforced against local buckling with a stiffener plate. The second part consists of a triangular gusset plate which is welded to the beam flange. Two bolts acting in shear connect the gusset plate to the web of the T-section. This way the connection can act in tension or compression. Experimental pull-out tests on individual connections allowed their load deflection characteristics to be established. A full scale experiment was performed on a one-storey one-bay 3 by 3 m infilled frame structure which was horizontally loaded at the top. With the characteristics of the frame-to-panel connections obtained from the experiments on individual connections, finite element analyses were performed on the infilled frame structures taking geometric and material non-linear behaviour of the structural components into account. The finite element model yields reasonably accurate results. This allows the model to be used for further parametric studies.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.314-323
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• 2010

Recently, granular soils having a large particle size are frequently used as a filling material in the construction of foundation, harbor, dam, and so on. The shear behavior of this granular soil plays a key role in the stability of structures. For example, soil particle crushing occurring at the interface between structure and soil and/or within soil mass can cause the disturbance of ground characteristics and consequently induce an issues in respect of stability of structures. In order to investigate the shear behavior according to an existence and nonexistence of particle crushing, numerical analyses were conducted by using the DEM(Discrete Element Method)-based software program PFC(Particle Flow Code). Using the crushing model and non-crushing model which were created in this study, numerical analyses of ring shear test were conducted and their results were analyzed and compared. In general, landslide and slope stability are accompanied by a large displacement and consequently not only a peak strength but also a residual strength are very important in the analysis of landslide and slope stability. However the direct shear test which has been commonly used in the determination of shear strength parameters has a limitation on displacement therefore the residual strength parameters can not be obtained. The characteristics of residual shear behavior were investigated through the numerical analyses in this study.