• Earthquakes and Structures
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• 제17권5호
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• pp.463-475
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• 2019

In this paper, a procedure to develop fragility curves of structures equipped with semi-active tuned mass dampers (SATMDs) considering multiple failure criteria has been presented while accounting for the uncertainties of the input excitation, structure and control device parameters. In this procedure, Latin hypercube sampling (LHS) method has been employed to generate 30 random SATMD-structure systems and nonlinear incremental dynamic analysis (IDA) has been conducted under 20 earthquakes to determine the structural responses, where failure probabilities in each intensity level have been evaluated using Monte Carlo simulation (MCS) method. For numerical analysis, an eight-story nonlinear shear building frame with bilinear hysteresis material behavior has been used. Fragility curves for the structure equipped with optimal SATMDs have been developed considering single and multiple failure criteria for different performance levels and compared with that of uncontrolled structure as well as structure controlled using passive tuned mass damper (TMD). Numerical analysis has shown the capability of SATMDs in significant enhancement of the seismic fragility of the nonlinear structure. Also, considering multiple failure criteria has led to increasing the fragility of the structure. Moreover, it is observed that the influence of the uncertainty of input excitation with respect to the other uncertainties is considerable.

• 소성∙가공
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• 제21권2호
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• pp.113-118
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• 2012

Magnesium sheet alloys possess limited plastic formability at room temperature but their formability is substantially improved at elevated temperatures and optimum strain rates. In the present paper, three different types of failure criteria, namely, strain-based, stress-based, and work-based criteria, are compared for their applicability to warm press forming of magnesium sheet alloys. Warm deep-drawing experiments were conducted on AZ31 alloy sheet, and the results were used to assess the strength and weakness of the failure criteria.

• 한국해양공학회지
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• 제25권2호
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• pp.92-100
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• 2011

The main goal of this paper is to provide the theoretical background for the fracture phenomena in marine structural steels. In this paper, various fracture criteria are theoretically investigated: shear failure criteria with constant failure strain and stress triaxiality-dependent failure strain (piecewise failure and Johnson-Cook criteria), forming limit curve failure criterion, micromechanical porosity failure criterion, and continuum damage mechanics failure criterion. It is obvious that stress triaxiality is a very important index to determine the failure phenomenon for ductile materials. Assuming a piecewise failure strain curve as a function of stress triaxiality, the numerical results coincide well with the test results for smooth and notched specimens, where low and high stress triaxialities are observed. Therefore, it is proved that a failure criterion with reliable material constants presents a plastic deformation process, as well as fracture initiation and evolution.

• 대한기계학회논문집A
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• 제31권3호
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• pp.304-312
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• 2007

The objective of this study is to develop a local failure criterion for a wall thinning defect of piping components. For this purpose, a series of tensile tests was performed using several types of simulated specimens with different stress states, including smooth round bar, notched round bar (five different notch radii), and grooved plate (three different groove radii). In addition, finite element (FE) simulations were performed on the simulated specimen tests and the results were compared with the test results. From the comparisons, the equivalent stress and strain corresponding to maximum load and final failure of notched specimens were proposed as failure criteria under tensile load. The criteria were verified by employing them to the estimation of failure of grooved plate specimens that simulate the wall thinning defect. It showed that the proposed criteria accurately estimate the maximum load and final failure of grooved plate specimen tests.

• Computers and Concrete
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• 제28권6호
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• pp.585-603
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• 2021

The validation based on the experimental data demonstrates that the concrete strength under triaxial compression (TC) is overestimated by Lubliner-Oller strength criterion (SC) but underestimated by Lubliner-Lee SC in ABAQUS. Moreover, the discontinuous derivatives of failure criterion exists near the unexpected breakpoints. Both resulted from the piecewise linear meridians of the original Lubliner SC with constants γ. Following the screen for the available failure criteria to determine the model parameter γ of Lubliner SC, Menétrey-Willam SC (MWSC) is considered the most promising option with a reasonable aspect ratio Kc but no other strength values required and only two new model parameters introduced. The failure surface of the new Lubliner SC based on MWSC (Lubliner-MWSC) is smooth and has no breakpoints along the hydrostatic pressure (HP) axis. Finally, predicted results of Lubliner-MWSC are compared with other concrete failure criteria and experimental data. It turns out that the Lubliner-MWSC can represent the concrete failure behavior, and MWSC is the optimal choice to improve the applicability of the concrete damaged plasticity model (CDPM) under TC in ABAQUS.

• Journal of Advanced Research in Ocean Engineering
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• 제1권4호
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• pp.211-226
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• 2015

Membrane type Mark III cargo containment system (CCS) is considered in this study to investigate its strength capability under applied loads due to liquefied natural gas (LNG) cargo. A rectangular plated structure supported by inner hull structure is exemplified from Mark III CCS according to classification society's guidance and it is assumed as multi-layered structure by stacking plywood, triplex, reinforced polyurethane (PU) foam and series of mastic upon inner hull structure. Commercially available general purpose finite element analysis package is used to have reliable FE models of Mark III CCS plate. The FE models and anisotropic failure criteria such as maximum stress, Hoffman, Hill, Tsai-Wu and Hashin taking into account the direction dependent material properties of Mark III CCS plate components and their material properties considering a wide variation of temperature due to the nature of LNG together form the strength analysis procedure of Mark III CCS plate. Strength capability of Mark III CCS plate is understood by its initial failure and post-initial failure states. Results are represented in terms of failure loads and locations when initial failure and post-initial failures are occurred respectively. From the results the basic design information of Mark III CCS plate is given.

• Structural Engineering and Mechanics
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• 제5권4호
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• pp.433-450
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• 1997

The objective of this work is to predict the failure loads, associated maximum transverse displacements, locations and the modes of failure, including the onset of delamination, of thin, flat, square symmetric laminates under the action of uni-axial compression. Two progressive failure analyses, one using Hashin criterion and the other using Tensor polynomial criteria, are used in conjunction with the finite element method. First order shear deformation theory and geometric nonlinearity in the von Karman sense have been employed. Five different types of lay-up sequence are considered for laminates with all edges simply supported. In addition, two boundary conditions, one with all edges fixed and other with mixed boundary conditions for $(+45/-45/0/90)_{2s}$ quasi-isotropic laminate have also been considered to study the effect of boundary restraints on the failure loads and the corresponding modes of failure. A comparison of linear and nonlinear results is also made for $({\pm}45/0/90)_{2s}$ quasi-isotropic laminate. It is observed that the maximum difference between the failure loads predicted by various criteria depend strongly on the laminate lay-ups and the flexural boundary restraints. Laminates with clamped edges are found to be more susceptible to failure due to the transverse shear and delamination, while those with the simply supported edges undergo total collapse at a load slightly higher than the fiber failure load.

• 콘크리트학회논문집
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• 제16권3호
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• pp.345-356
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• 2004

다양한 압축 응력 상태에서의 콘크리트의 거동 특성을 나타내기 위한 소성 모델을 개발하였다. 응력 성분은 압축 상태에서 각각의 거동특성을 갖는 세 개의 직교 성분으로 분리하였다. 각 성분의 거동 특성을 독립적으로 나타내기 위하여 각 성분에 대한 독립적인 다중 파괴기.준을 이용하는 소성모델을 적용하였다. 각 파괴면은 실험결과에 근거하여 각 파괴기준에 대한 등가 소성 변형률에 의하여 정의하였다. 또한, 압축손상에 의한 체적팽창을 나타내기 위한 간단한 비상관 소성흐름법칙을 제안하였다. 제안된 모델은 다양한 재료 특성 및 응력 상태를 갖는 기존의 실험 결과들과 비교를 통하여 검증되었다. 이 비교는 기존의 소성모델보다 제안된 모델의 적용성이 우수함을 입증하고 있다.

• 대한기계학회논문집A
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• 제36권7호
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• pp.769-776
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• 2012

본 논문의 유한요소 손상해석기법은 재료 인장물성과 파괴기준을 필요로 한다. 기존에 연구된 재료들은 노치인장 시험결과로부터 하나의 인장물성과 파괴기준을 구할 수 있었다. 그러나 본 논문에서 사용된 cast stainless steel(CF8M)의 경우, 동일한 조건의 노치인장 시험결과들에 분산이 존재하여 해석자에 따라 다른 인장물성과 파괴기준이 구해질 수 있다. 따라서 해석자에 관계없이 일관된 인장물성 및 파괴기준을 구할 수 있는 적절한 절차가 필요하다. 본 논문에서는 노치반경 16mm 의 인장시편 시험결과로부터 평균 인장물성을 구하였고, 이를 유한요소 해석에 적용하여 3 개의 파괴기준을 구하였다. 구해진 인장물성과 파괴기준을 적용하여 J-R 파괴인성 시험에 대한 손상해석을 수행하였고, 시험결과와 비교함을 통해 제시된 절차의 타당성을 검증하였다.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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• pp.529-534
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• 1998

To find out an adequate failure criterion in two-dimensional linear elastic crack problems, finite element programs, SED, which determine stress intensity factors $K_I, K_{II}$, crack angle and peak load by the minimum strain energy density failure criterion were developed. In this program, the conventional quadratic isoparametric elements were used in all regions except the crack tip zone where triangular singular elements with 6 nodes were used. The results of SED were compared with the results of those which followed by the maximum circumferential tensile stress criteria and those by the maximum energy release rate criteria and those by Jenq and Shah`s experiments of the same geometry and material properties. The maximum energy release rate criteria were better close to those of the Jenq and Shah`s experiments than the maximum circumferential tensile stress criteria and the minimum strain energy density criteria.