• 펄프종이기술
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• 제30권1호
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• pp.29-43
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• 1998

This study was to investigate the effect of .compressive load and cyclic humidity(2$0^{\circ}C$, 65% and 90% RH) on the physical and mechanical properties of corrugated board. Corrugated boards in the study were under compressive load and under cyclic humidity, and their properties were compared to those without load. Results were summarized as follows ; 1 Statistically significant correlation was shown between the ring crush of the boards and the compressive strength of cylinder specimen made from the boards. So we could study the compressive behavior of board with cylinder specimen. 2. The boards under the compressive load increased their moisture content and thickness much more than those without load both in constant and in cyclic RH. 3. The compressive and tensile strength of board samples were inversely and closely proportional to the sheet moisture content regardless of their load and humidity history. 4. The moisture content did not show any significant proportionality to the change of burst strength of boards within this experiment. 5. Board reconditioning in standard condition led to the recovery of the strength loss that had occurred under various load and humidity condition. 6. The handsheets prepared from the boards that had experienced compressive load and cyclic humidity, and those with no-load and 65% RH did not show any significant difference in strength properties. No physical damage or load-carrying properties of the wood fiber were observed by the compressive load and cyclic humidity history.

• Journal of the Korean Wood Science and Technology
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• 제50권1호
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• pp.68-80
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• 2022

Timber boardwalk decks are widely installed in parks and scenic areas to provide pedestrians an elevated footpath as well as harmony with the surrounding natural scene. In order to extend the lifespan of boardwalks in the outdoor environment, industrially treated pine timber, such as Pinus sylvestris, is often adopted. However, accidents of pedestrians injured by damaged boardwalk decks have been constantly reported. Therefore, the mechanical behavior of two different types of treated timber was examined in this study under repeated wetting and drying. An increasing number of radial cracks appeared with increasing length and width as more cycles were performed. A loss of more than 40% of the screw withdrawal capacity was observed in both end grain and face grain for the two types of timber after twelve accelerated wet-dry cycles, which coincides with the observation of damaged timber boardwalks in the field investigation. At the same time, it was found that both the compressive and the flexural strength was not sensitive to the wet-dry cycles especially at large cycle numbers.

• Geomechanics and Engineering
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• 제31권1호
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• pp.87-97
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• 2022

The excessive settlement and deformation of disintegrated carbonaceous mudstone (DCM) embankments under dynamic loading have long been problems for engineers and technicians. In this work, the characteristics and mechanism of the plastic deformation of DCM under different degrees of compaction, water contents and confining pressures were studied by static triaxial, dynamic triaxial and scanning electron microscopy testing. The research results show that the axial stress increases with increasing confining pressure and degree of compaction and decreases with increasing water content when DCM failure. The axial strain at failure of the DCM decreases with increasing confining pressure and degree of compaction and increases with increasing water content. Under cyclic dynamic stress, the change in the axial stress level of the DCM can be divided into four stages: the stable stage, transition stage, safety reserve stage and unstable stage, respectively. The effects of compaction, water content and confining pressure on the critical axial stress level which means shakedown of the DCM are similar. However, an increase in confining pressure reduces the effects of compaction and water content on the critical axial stress level. The main deformation of DCM is fatigue cracking. Based on the allowable critical axial stress, a method for embankment deformation control was proposed. This method can determine the degree of compaction and fill range of the embankment fill material according to the equilibrium moisture content of the DCM embankment.

• Computers and Concrete
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• 제15권2호
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• pp.183-198
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• 2015

Chloride ingress implies a complex interaction between physical and chemical process, in which heat, moisture and chloride ions transport through concrete cover. Meanwhile, reinforced concrete structure itself undergoes evolution due to variation in temperature, relative humidity and creep effects, which can potentially change the deformation and trigger some micro-cracks in concrete. In addition, all of these process show time-dependent performance with complex interaction between structures and environments. In the present work, a time-dependent behavior of chloride transport in reinforced concrete beam subjected to flexural load is proposed based on the well-known section fiber model. The strain state varies because of stress redistribution caused by the interaction between environment and structure, mainly dominated by thermal stresses and shrinkage stress and creep. Finally, in order to clear the influence of strain state on the chloride diffusivity, experiment test were carried out and a power function used to describe this influence is proposed.

• 한국농공학회지
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• 제34권4호
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• pp.69-79
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• 1992

To estimate soil behavior and structural characteristics under the conditions of cyclic loading, freezing & thawing and initial state, several testing was performed and obtained following results. 1.After repeated freezing and thawing processes, original soil structure was destroyed and changed to globular structure from honeycomb or tube in its structure types. Also above processes resulted increasing the soil compression strain while decreasing the failure stress in stress-strain relationship and reached the soil structure into the mode of brittle fracture. Under cyclic loading conditions, soil cluster which was originally dispersed structure colloided with each other, seperated, and finally the soil failed due to the effect of overcompaction. 2.Through the stabilization processes seperated by four steps, the structure of soil skeleton was changed to quite different globular type. The degree of compressibility of soil was decreased in the normally consolidated zone, while the strength against external load increased due to soil particle stabilization. 3.Soil stress-strain chracteristics were largely influenced by repeated up and down processes of temperature. The maximum deformation was obtained in the case of temperature between 0 10˚C by the reseon of particle cluster reformation. 4.Soil compressibility was largely influenced by the optimum moisture content. Under freezing process, swelling could be found and its magnitude was proportional to the density of soil. 5.Density of soil was decreased as increasing the number or repeated freezing and thawing processes and the largest decreasing rate was found at the first turning point from freezing to thawing cycle.

• 한국식품조리과학회지
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• 제26권1호
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• pp.62-71
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• 2010

감초분말을 첨가하여 된장을 제조한 후 관능특성 및 이화학적 품질특성을 조사한 결과는 다음과 같다. 전반적인 기호도는 소금 농도 20%, 감초분말 4%(LD204) 첨가한 된장과 소금 농도 16%, 감초분말 2%(LD162) 첨가하여 제조한 된장이 우수하였다. 수분함량 변화는 대조군은 수분함량에 변화가 없었으나, LD204와 LD162는 숙성 1주일째 수분함량이 감소한 후 이후에는 거의 변화가 없었다. pH는 0일째 5.90~5.97로 비슷하였으나, 5주째 대조군은 5.90에서 5.72로 낮아졌으며, LD204는 0일째 5.95에서 1주째 5.42로 낮아진 이후 다시 서서히 높아져 5주째 5.93 으로 0일째와 비슷하였다. LD162는 0일째 5.97에서 1주째 소폭 증가 감소를 반복하여 5주째 6.32로 0일째보다 증가하였으며, LD204보다 pH가 높았다. 산도는 담금 직후부터 차이를 나타내어 대조군은 0일째 0.16%에서 서서히 증가하여 4주째 젖산 함량이 0.59%로 가장 높았으며 5주째는 소폭 감소하였다. LD204는 0일째 0.25%에서 서서히 증가하여 4주째 젖산 함량이 0.50%로 가장 높았으며 5주째 소폭 감소하여 대조군과 비슷한 경향이었다. LD162는 0일째 0.22%에서 서서히 증가하여 3주째 0.49로 가장 높았으며 4주 이후 감소하는 경향이었다. 염도는 0일째 대조군이 29.5%, LD204는 22.0%, LD162는 18%였으나 5주째 각각 34.0%, 29.0% 및 26.0%로 증가하였다. 당도는 0일째 대조군이 $32^{\circ}Brix$, LD204는 $28^{\circ}Brix$, LD162는 $26^{\circ}Brix$였으나 5일째 각각 $40^{\circ}Brix$, $32^{\circ}Brix$ 및 $30^{\circ}Brix$로 소폭 증가하였다. 재래된장보다 높은 염도에서 관능점수가 높게 나온 것은 감초의 감미 때문인 것으로 판단되나 앞으로 염도를 조금 더 낮춰준다면 약리성을 가지는 장류가 될 수 있을 것으로 판단된다.