• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1997년도 봄 학술발표회 논문집
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• pp.430-435
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• 1997

This paper represents the investigation of the shear fatigue behavior and damage procedure of reinforced concrete beams subject to repeated loading using the strut-tie model. Damage Index is defined as the ratio of deflection at each cycle to the ultimate deflection of inelastic region. Two types of strut-tie model are designed according to the inclined angles of concrete-struts and the consideration of concrete-ties. In one model, aggregate interlock and resistance of uncracked concrete are regarded as the main sheat resisting mechanism and in the other, stirrup is. The results show that the strut-tie model combined with damage index can describe the shear fatigue behavior of RC beams subject to repeated loading effectively.

• Steel and Composite Structures
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• 제46권4호
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• pp.485-495
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• 2023

Bending static and stress investigation of a microplate of piezoelectric/piezomagnetic material subjected to combined multifield loading. Shear deformable as well as thickness stretched model is used for derivation of the kinematic relations. Multi field governing equations are derived analytically through principle of virtual work. the results are analytically obtained analytically including magnetic/electric potentials, displacement and stress components with variation in multifield loading parameters.

• Steel and Composite Structures
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• 제47권1호
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• pp.121-134
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• 2023

This paper tested 11 concrete-encased concrete-filled steel tube (CFST) composite columns and one reinforced concrete column under combined axial compression and lateral loads. The primary parameters, including the loading system, axial compression ratio, volume stirrup ratio, diameter-to-thickness ratio of the steel tube, and stirrup form, were varied. The influence of the parameters on the failure mode, strength, ductility, energy dissipation, strength degradation, and damage evolution of the composite columns were revealed. Moreover, a two-parameter nonlinear seismic damage model for composite columns was established, which can reflect the degree and development process of the seismic damage. In addition, the relationships among the inter-story drift ratio, damage index and seismic performance level of composite columns were established to provide a theoretical basis for seismic performance design and damage assessments.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2000년도 춘계학술발표대회 논문집
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• pp.1-4
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• 2000

This paper addresses a modified arc-length method for the nonlinear finite element analysis of a structure which is loaded in incremental and fixed forces, simultaneously. The main idea of the method is to separate the displacement term by the constant force from that by the incremental force. As the illustrative examples of the applicability of the present algorithm, a parametric study is performed on the nonlinear buckling behavior of composite cylindrical panels under the combined load of the incremented compression and the constant lateral pressure.

• Fibers and Polymers
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• 제3권1호
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• pp.31-37
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• 2002

Most fibers are irregular, and they are often subjected to combined loading conditions during processing and enduse. In this paper polyester and wool fibers under the combined tensile and torsional loads have been studied for the first time using the finite element method (FEM). The dimensional irregularities of these fibers are simulated with sine waves of different magnitude and frequency. The breaking load and breaking extension of the fibers at different twist or torsion levels are then calculated from the finite element model. The results indicate that twist and level of fiber irregularity have a major impact on the mechanical properties of the fiber and the effect of the frequency of irregularity is relatively small.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.233-236
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• 2002

An efficient method was developed in this study to obtain optimal stacking sequences, thicknesses, and minimum weights of stiffened laminated composite shells under combined loading conditions and stiffener layouts using genetic algorithms (GAs) and finite element analyses. Among many parameters in designing composite laminates determining a optimal stacking sequence that may be formulated as an integer programming problem is a primary concern. Of many optimization algorithms, GAs are powerful methodology for the problem with discrete variables. In this paper the optimal stacking sequence was determined, which gives the maximum critical buckling load factor and the minimum weight as well. To solve this problem, both the finite element analysis by ABAQUS and the GA-based optimization procedure have been implemented together with an interface code. Throughout many parametric studies using this analysis tool, the influences of stiffener sizes and three different types of stiffener layouts on the stacking sequence changes were throughly investigated subjected to various combined loading conditions.

• Steel and Composite Structures
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• 제27권2호
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• pp.243-253
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• 2018

In recent years, concrete-filled box or tubular columns have been commonly used in high-rise buildings. However, a number of fire test results show that there are significant differences between high strength concrete (HSC) and normal strength concrete (NSC) after being subjected to high temperatures. Therefore, this paper presents an investigation on the fire resistance of HSC filled steel tubular columns (CFTCs) under combined temperature and loading. Two groups of full-size specimens were fabricated to consider the effect of type of concrete infilling (plain and reinforced) and the load level on the fire resistance of CFTCs. Prior to fire test, a constant compressive load (i.e., load level for fire design) was applied to the column specimens. Thermal load was then applied on the column specimens in form of ISO 834 standard fire curve in a large-scale laboratory furnace until the set experiment termination condition was reached. The results demonstrate that the higher the axial load level, the worse the fire resistance. Moreover, in the bar-reinforced concrete-filled steel tubular columns, the presence of rebars not only decreased the spread of cracks and the sudden loss of strength, but also contributed to the load-carrying capacity of the concrete core.

• 한국임상약학회지
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• 제15권2호
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• pp.105-117
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• 2005

Following intracoronary stenting, antiplatelet therapy lead to greater protection from thrombotic complication. A few data are available about the effect of clopidogrel versus cilostazol, an antiplatelet commonly used after intracoronary stenting. To evaluate the efficacy and safety of clopidogrel plus aspirin compared with those of cilostazol plus aspirin in coronary stenting and to evaluate the efficacy of clopidogrel loading dose prior to coronary stealing in clopidogrel group. Data were retrospectively collected from medical charts of patients who had undergone coronary stenting and received either clopidogrel with or without loading 300 mg followed by 75 mg/d (n=58), or 200 mg/d cilostazol(n=72) for 1 year, between January 2000 and May 2002. All patients in both groups received aspirin 200 mg/d throughout the study. The primary endpoints at 7, 30, 180 and 365 days after stealing were the composite of death, Myocardial Infarction, stroke, angina, and revascularization in the intent to treat population and restenosis at follow up angiography. The secondary endpoints were the incidence of bleeding complications at 7, 30, and 365 days, and durg adverse effects at 365 days after stenting. At 180 and 365 days after stenting, the combined primary endpoints were significantly reduced in clopidogrel plus aspirin group (relative risk 0.39; 95% CI 0.17 to 0.92; p=0.021, RR 0.43; 95% CI 0.22 to 0.84; p=0.0085, respectively). However, the combined primary endpoints were not significantly different between the two groups at 7 and 30 days (p:1.00, p=0.79, respectively). Angiographic restenosis rate was 14.3% in clopidogrel plus aspirin uoup and 32.1% in cilostazol plus aspirin group (p=0.19). 300mg of clopidogrel loading dose did not significantly reduce the combined primary endpoints at 30 days after stenting (RR 0.14; 95% CI 0.01 to 2.65; p=0.23). The rate of bleeding complications and drug adverse effects were not different between the two groups. In patients undergoing intracoronary stenting, clopidogrel plus aspirin therapy is more beneficial than cilostazol plus aspirin in reducing major adverse cardiac events with similar rate of bleeding complication. A loading dose of clopidogrel did not lead to a statistically significant reduction in major adverse cardiac events.

• 한국철도학회논문집
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• 제3권3호
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• pp.117-124
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• 2000

The rubber wheel-type AGT has two major kinds of bogie; one is the bogie type and the other steering one. Both are important vehicular structure to support the whole running vehicle and passenger loads. This paper deals with the static analysis for the two types of bogie frame subjected to combined external forces, as well as independent ones specified in UIC 515-4. Furthermore, the dynamic analysis is performed under vibrational loading conditions so as to compare dynamic characteristics, Numerical results by using commercial packages, I-DEAS and NASTRAN show that maximum stresses do not exceed the yield strength level of material used for both bogies. From an overall viewpoint of strength, the bogie type turns out to be superior to the steering type except for the case of a lateral loading. It is also observed that the steering type shows a characteristics of low frequency behavior during a course of searching for structurally weak areas to be stiffened. The vibrational fatigue analysis for each bogie frame depends on the loading time history conditions which is applied. Time History Central Database List in the NASTRAN package. Subsequent1y, the fatigue life of bogie type is longer than the steering type.

• Steel and Composite Structures
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• 제37권5호
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• pp.533-549
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• 2020

Recently, Concrete-filled double skin steel tubular (CFDST) columns have proven an exceptional structural resistance in terms of strength, stiffness, and ductility. However, the resistance of these column members can be severely affected by the type of loading in which bending stresses increase in direct proportion with axial load and eccentricity value. This paper presents a non-linear finite element based modeling approach that studies the behavior of slender CFDST columns under biaxial loading. Finite element models were calibrated based on the outcomes of experimental work done by other researchers. Results from simulations of slender CFDST columns under axial loading eccentric in one direction showed good agreement with the experimental response. The calibrated models are expanded to a total of thirty models that studies the behavior of slender CFDST columns under combined compression and biaxial bending. The influences of parameters that are usually found in practice are taken into consideration in this paper, namely, eccentricity-to-diameter (e/D) ratios, slenderness ratios, diameter-to-thickness (D/t) ratios, and steel contribution ratios. Finally, an analytical study based on current code provisions is conducted. It is concluded that South African national standards (2011) provided the most accurate results contrasted with the Eurocode 4 (2004) and American Institute of Steel Construction (2016) that are found to be conservative. Accordingly, correction factors are proposed to the current design guidelines to provide more satisfactory results.