• Earthquakes and Structures
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• 제14권1호
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• pp.11-20
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• 2018

Three-dimensional panels are one of the modern construction systems which can be placed in the category of industrial buildings. There have always been a lot of studies and efforts to identify the behavior of these panels and improve their capacity due to their earthquake resistance and high speed of performance. This study will provide a comparative evaluation of behavior of updated three-dimensional panel's structural components under lateral load in both independent and dependent modes. In fact, this study tries to simultaneously evaluate strengthening effect of three-dimensional panels and the effects of system state (independent, L-shaped and BOX shaped Walls) with reinforcement armatures with different angles on the three-dimensional panels. Overall, six independent wall model, L-shaped, roofed L-shaped, BOX-shaped walls with symmetric loading, BOX -shaped wall with asymmetrical loading and roofed BOX-shaped wall were built. Then the models are strengthened without strengthened reinforcement and with strengthened reinforcements with an angle of 30, 45 and 60 degrees. The applied lateral loading, is exerted by changing the location on the end wall. In BOX-shaped wall, in symmetric and asymmetric loading, the load bearing capacity will be increased about 200 and 50% respectively. Now, if strengthened, the load bearing capacity in symmetric and asymmetric loading will be increased 3.5 and 2 times respectively. The effective angle of placement of strengthened reinforcement in the independent wall is 45 and 60 degrees. But in BOX-shaped and L-shaped walls, the use of strengthened reinforcement 45 degrees is recommended.

• 한국축산시설환경학회지
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• 제4권2호
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• pp.167-174
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• 1998

It is known that the anaerobic fermentation of organic matter (OM) is divided into 2 phases, acidogenic phase in which OM is digested into volatile fatty acid (VFA), and methanogenic phase where the produced VFA is converted to CH4 and CO2. In a natural fermenting procedure, these 2 phases occur at the same time. However the total production of end products (methane) may be limited if these 2 phases occur at the same time. This is believed to be due to the difference in growth rate, substrate-utilizing efficiency and favorable environment for each microbes (acidogens and methanogens), involved in each phase. It is therefore suggested for the maximum recycling of organic waste (such as animal waste) through providing 2 different steps in fermenting procedure, acidogenic phase and methanogenic phase, in each case the activity of involved microbes can be maintained at the maximum level. The results obtained from these experiments are summarized as follows : The loading rates of swine waste were made through 2.5, 5 and 10 gVS / l / d to identify its acidogenic fermenting character in this study. The VFA yield was maximized at 10 gVS / l / d of loading rate. On the basis of this study was executed to identify the optimum HRT of 1, 2 and 4 days at 10 gVS / l / d of loading rate in acidogenic phase. The maximum VFA yield was obtained at 1 days of HRT.

• Structural Engineering and Mechanics
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• 제78권5호
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• pp.573-583
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• 2021

This paper presents a theoretical approach of the structures reinforced with bonded FRP composites, taking into account loading model, shear lag effect and the thermal effect. These composites are used, in particular, for rehabilitation of structures by stopping the propagation of the cracks. They improve rigidity and resistance, and prolong their lifespan. In this paper, an original model is presented to predict and to determine the stresses concentration at the FRP end, with the new theory analysis approach. The model is based on equilibrium and deformations compatibility requirements in and all parts of the strengthened beam, i.e., the concrete beam, the FRP plate and the adhesive layer. The theoretical predictions are compared with other existing solutions. The numerical resolution was finalized by taking into account the physical and geometric properties of materials that may play an important role in reducing the stress values. This solution is general in nature and may be applicable to all kinds of materials.

• Geomechanics and Engineering
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• 제5권3호
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• pp.195-221
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• 2013

A centrifuge model study is carried out to investigate the behavior of pile subject to negative skin friction induced by pile installation, ground water drawdown and surcharge loading. A single end-bearing pile is examined as the induced negative skin friction would induce the most severe stress on the pile structural material as compared to friction piles. In addition, the behavior of the pile under simultaneous negative skin friction and dead/live loads is examined. To facilitate detailed interpretations of the test results, the model setup is extensively instrumented and involves elaborate test control schemes. To further examine the phenomenon of negative skin friction on an end-bearing pile, finite element analyses were conducted. The numerical analysis is first validated against the centrifuge test data and subsequently extended to examine the effects of pile slenderness ratio, surcharge intensity and pile-soil stiffness ratio on the degree of mobilization of negative skin friction induced on the pile. Finally experimental and numerical studies are conducted to examine the effect of applied transient live load on pile subject to negative skin friction.

• 복합신소재구조학회 논문집
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• 제4권3호
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• pp.7-12
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• 2013

The demand for the structural system of reduction of story height increases because buildings are getting higher. The existing structural systems are not efficiency. Thus, it is hard to reduce the story height and existing methods cannot secure economics as expected. This study aims at developing the partially concrete-filled new type composite beam, which can efficiently resist against the end negative moment and central positive moment, also reduce deflection of beams. Through case studies on loading of concentrated load and uniformly distributed load to fixed beam, we could find the most efficient ratio of moment of inertia and the ratio ${\alpha}$(end beam length to span). The gap space between middle and end beam can be used as facilities installation, consequently the suggested Omega beam system is expected to get the effect of reduction in story height as well as reduction of quantity.

• Smart Structures and Systems
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• 제22권6호
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• pp.663-673
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• 2018

In this study, the effect of particle size on the cracks propagation and coalescence or cracking pattern of the edge notched disc specimens are investigated. Firstly, calibration of PFC3D was performed using Brazilian experimental test output. Then micro parameters were used to build edge notched disc specimen. The horizontal wall of the assembly is let to move downward with a standard low speed of 0.016 m/s. The numerical results show that the tensile cracks are dominant failure pattern for the modeled discs. These tensile cracks initiate from the pre-existing notch tip and propagate parallel to the loading direction then interact with the upper boundary of the modeled specimen. As the size of the balls (ball diameter) decrease the number of tensile cracks increase. The tensile fracture toughness of the samples also decreases as the particle size increases. Understanding the crack propagation and crack coalescence phenomena in brittle materials such as concretes and rocks is of paramount importance in the stability analyses for engineering structures such as rock slopes, underground structures and tunneling.

• 한국지반공학회논문집
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• 제39권3호
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• pp.5-16
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• 2023

본 연구는 기초판의 연성률이 말뚝지지 전면기초에 미치는 영향을 해석적 연구와 수치해석으로 분석했다. 기초판의 연성률(K_R)과 선단지지 조건에 따른 말뚝과 기초판의 하중 분담률을 분석했다. 각각의 말뚝과 전체적인 응답은 3차원 유한 요소 해석법을 사용하여 분석했다. 본 연구에서 수직 하중이 증가하고 기초판의 연성률이 감소함에 따라 말뚝지지 전면기초의 하중분담비(α_pr)가 감소하는 것으로 나타났다. 이러한 경향은 선단지지 말뚝을 사용하는 것보다 마찰말뚝을 사용하는 경우에 더 뚜렷하게 나타났다. 또한, 연성 기초판의 경우, 하중조건에 따른 말뚝 위치별 축력 분포경향은 큰 차이를 보이지 않았으나, 강성 기초판의 경우, 하중조건에 따라 외곽에 위치한 말뚝 두부 축력이 증가하는 경향을 보였다. 기초판의 침하는 연성 기초판 조건이 강성 기초판보다 더 크게 나타났으며, 이로 인해 연성 기초판 조건에서 하중분담비가 감소하는 것으로 나타났다.

• 한국전산구조공학회논문집
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• 제13권2호
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• pp.245-256
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• 2000

이 논문에서는 반복하중을 받는 철근콘크리트 보의 거동을 모사하기 위한 모멘트-곡률 관계를 제안하고 있다. 기존의 제안된 모멘트-곡률 관계 모델이나 적층단면법과는 달리 제안된 모델은 부착-슬립관계와 상응하는 평형방정식을 기초로 하여 구성된 단조증가 하중에 대한 모멘트-곡률 관계를 이용하여 부착-슬립에 따른 영향을 고려하고 있다. 또한 대변형 해석시 보다 개선된 결과를 얻기 위해 철근의 응력-변형률 관계에 착안한 곡선화 된 천이곡선을 사용하고 있다. 응력-변형률 관계에 기초하여 단면을 가상의 층상구조로 모사하는 적층단면법과 비교하여 제안된 모델은 단면의 거동을 모멘트-곡률 관계로 표현하는 관계로 대형구조물의 해석시 계산시간과 저장공간을 줄일 수 있는 잇점을 가지고 있다. 나아가 고정단회전과 pinching효과를 고려하기 위한 제안된 기본모델의 수정방안이 소개되고 있다. 마지막으로 제안된 모델식의 타당성을 검증하기 위하여 해석결과와 실험값들의 비교가 이루어졌다. 본 논문은 구조물의 미시적 측면에서 유효평균탄성계수를 결정하기 위한 균질화기법인 점근적 방법을 적용하였고, 탄성값을 조사하기 위하여 유한요소법으로 정식화하였다. 수치 예로서 물성치가 각기 다른 등방성 재료를 적층한 부재의 임의 단면에서 단위요소를 해석영역으로 설정하고 산출된 탄성계수를 기존의 해석방법으로부터 산출된 값과 비교하였다. 균질화기법으로 산출된 탄성계수는 과소평가되어 나타나며, 이는 해석영역을 유한요소정식화하는 과정에서 수정항만큼 차이가 난다는 것을 증명하였다. 기존 해석방법으로는 복합재료의 탄성계수가 단순히 재료의 산술적 평균값으로 계산되는 것과는 달리, 미시적으로 복합재 단위요소의 반복성을 고려함으로써 제안된 해석방법이 보다 유용하다는 것을 보여 주었다.

• Nutrition Research and Practice
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• 제3권4호
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• pp.272-278
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• 2009

Postprandial hypoglycemic effect of mulberry leaf (Morus alba L.) was compared in two animal models: Goto-Kakizaki (GK) rats, a spontaneous non-obese animal model for type II diabetes, and their counterpart control Wistar rats. First, the effect of a single oral administration of mulberry leaf aqueous extract (MLE) on postprandial glucose responses was determined using maltose or glucose as substrate. With maltose-loading, MLE reduced peak responses of blood glucose significantly in both GK and Wistar rats (P < 0.05), supporting the inhibition of $\alpha$-glucosidase by MLE in the small intestine. With glucose-loading, MLE also significantly reduced blood glucose concentrations, measured at 30 min, in both animal models (P < 0.01), proposing the inhibition of glucose transport by MLE. Next, dried mulberry leaf powder (MLP) was administered for 8 weeks by inclusion in the diet. By MLP administration, fasting blood glucose was significantly reduced at weeks 4 and 5 (P < 0.05), but then returned to values that were similar to those of the control at the end of experimental period in GK rats. Insulin, HOMA-IR, C-reactive protein, and triglycerides tended to be decreased by MLP treatment in GK rats. All other biochemical parameters were not changed by MLP administration in GK rats. Collectively, these findings support that MLE has significant postprandial hypoglycemic effect in both non-obese diabetic and healthy animals, which may be beneficial as food supplement to manage postprandial blood glucose. Inhibitions of glucose transport as well as $\alpha$-glucosidase in the small intestine were suggested as possible mechanisms related with the postprandial hypoglycemic effect of MLE.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1636-1643
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• 2003

In this study, bolted joint made of Glass-Mat Reinforced Thermoplastics (GMT) specimen was under tensile loading to investigate the relation between joint strength and glass-fiber weight fraction of the flat plate specimen. The effect of molding conditions such as the initial size of a GMT charge and molding temperatures was investigated under plane strain condition. In consideration of the specimen geometry, minimum end distance and width of the specimen to induce the bearing fracture mode of the bolted joint were determined. And finally, the effect of the outer diameter of washer and clamping pressure on joint strength was also investigated. Since joint strength is dependent on the local glass-fiber weight fraction, experimentally measured strength was modified, considering its irregular values of the specimen molded under various processing conditions in order to obtain a reasonable correlation between the two.