• 한국임상수의학회지
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• 제18권3호
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• pp.189-194
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• 2001

The aim of this study was to investigate the anti-stress effect of xylazine on rope-restrained stress using cattle. For this study we utilized biotelemetrical methods such as body temperature, heart rate and blood analysis. Twelve cows were divided into two groups as an only rope restrained group (control) and as rope-restrain+xylazine (0.05 mg/kg, IV) treated group (experimental group). Each group was under experimental environments for 24 hours before initiation of stress. The body temperature and the heart rate were checked every 5 minutes for 24 hours in two groups. We found that the core body temperature in the experimental group was higher than that of control group. We also found hat the heart rate in experimental group was significantly lower (p<0.05) than that of control group for 90 minutes after 30 minutes of rope-restrained stress. The level of the plasma cortisol of experimental group was significantly lower (p<0.05) than that of control group for 90 minutes after the rope-restrained stress was given. We performed the blood analysis to know whether rope-restrained stress affects RBC, WBC, hemoglobin, hematocrit, and platelet values or not but we could not find the significant difference between control and experimental groups. These results suggest that the administration of xylazine might partially help to reduce rope-restrained stress in cattle.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
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• pp.315-320
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• 1998

The experimental set-up and one-dimensional analytical model have been developed to investigate the tensile behavior of reinforced concrete member due to restrained drying shrinkage. The experimental results have been compared with the analytical prediction of the maximum residual stress of steel and concrete due to restrained shrinkage. The tensile residual stress concrete by one-dimensional bilinear model shows 0.19 and 0.63 of tensile strength for 0.83% and 3.29 of steel ratio. The residual tensile stress of concrete increases as the steel ratio increases. The effect of steel fiber has not influenced the residual stress due to restrained shrinkage of concrete.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2018년도 추계 학술논문 발표대회
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• pp.27-28
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• 2018

In this study, water vapor pressure and restrained stress were evaluated by ring-type restrained condition for compressive strength 60 and 80MPa concrete. Experimental results show that the 80MPa concrete has higher water vapor pressure and restraint stress than the 60MPa concrete, resulting in spalling occurrence. It is because, the higher the compressive strength of the concrete, the more dense the internal structure is formed.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2016년도 추계 학술논문 발표대회
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• pp.28-29
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• 2016

By Testing restrained shrinkage, it is possible to estimating the cracking tendency of concrete such as time to cracking, tensile stress and tensile creep. In this study, tensile creep properties of concrete under restraint shrinkage were investigation through comparison of specimens that JIS and AASHTO proposed. As a results, tensile creep strains in concrete ring specimens were 15% higher than those in uniaxial specimens.

• 한국도로학회논문집
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• 제11권4호
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• pp.87-94
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• 2009

콘크리트 슬래브는 타설 후 온도와 수분 변화를 통해 체적이 변화한다. 수분증발에 의하여 발생한 건조수축은 슬래브의 자중이나 하부층과의 마찰 등에 의하여 구속되어 슬래브 내부에 응력이 유발된다. 선행 연구에 의하면 건조수축에 의하여 발생된 실제 인장응력은 이론적으로 예측된 값보다 작은 것으로 보고되었다. 이는 부분적으로 구속된 슬래브에서 발생하는 초기 재령 콘크리트의 점탄성에 기인한 응력감소 현상이다. 본 연구에서는 재령에 따른 콘크리트의 응력감소 현상을 조사하기 위하여 구속된 원주형, 구속되지 않은 자유건조 원주형, 그리고 자유건조 각주형 콘크리트 시편의 변형률을 측정하였다. 재령 1, 3, 7, 14, 28일에 콘크리트의 탄성계수를 측정하였으며 관입저항 실험을 실시하였다. 실험결과를 기존 연구자들이 제안한 이론식에 대입하여 구속된 원주형 콘크리트 시편의 응력감소를 계산할 수 있었다. 향후 본 연구의 결과를 바탕으로 구속된 콘크리트 시편의 응력감소 현상을 콘크리트 포장의 설계에 적용할 예정이다.

• Structural Engineering and Mechanics
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• 제4권4호
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• pp.383-396
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• 1996

In this paper, the behavior of plates partially restrained against rotation under stress gradient is investigated. As a first stage, an energy formulation is presented to model this boundary condition and a general expression is derived for the prediction of the elastic buckling of the plate under this general loading condition. The accuracy of the derived expression is compared numerically using the Galerkin method with other available data for the two limiting conditions of rotationally free and clamped boundaries. Results show that the prediction is within a 5% difference. The influence of rotational restraint and stress gradient upon the buckling load and the associated buckling mode is investigated. Numerical results show sensitivity of the buckling mode to the degree of rotational restraint and the variation of the buckling load with the stress gradient.

• Steel and Composite Structures
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• 제8권1호
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• pp.1-18
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• 2008

Observations from experiments and real fire indicate that restrained steel beams have better fire-resistant capability than isolated beams. Due to the effects of restraints, a steel beam in fire condition can undergo very large deflections and the run away damage may be avoided. In addition, axial forces will be induced with temperature increasing and play an important role on the behaviour of the restrained beam. The factors influencing the behavior of a restrained beam subjected to fire include the stiffness of axial and rotational restraints, the load type on the beam and the distribution of temperature in the cross-section of the beam, etc. In this paper, a simplified model is proposed to analyze the performance of restrained steel beams in fire condition. Based on an assumption of the deflection curve of the beam, the axial force, together with the strain and stress distributions in the beam, can be determined. By integrating the stress, the combined moment and force in the cross-section of the beam can be obtained. Then, through substituting the moment and axial force into the equilibrium equation, the behavior of the restrained beam in fire condition can be worked out. Furthermore, for the safety evaluation and repair after a fire, the behaviour of restrained beams during cooling should be understood. For a restrained beam experiencing very high temperatures, the strength of the steel will recover when temperature decreases, but the contraction force, which is produced by thermal contraction, will aggravate the tensile stresses in the beam. In this paper, the behaviour of the restrained beam in cooling phase is analyzed, and the effect of the contraction force is discussed.

• Journal of Acupuncture Research
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• 제20권3호
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• pp.177-193
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• 2003

Objective : The present studies investigated the effects of 120Hz high frequency electroacupunctue(EA) on the stress-induced stomach dysfunction in relation to its effect on the level of stress hormone and gastric mucosal damages. The gastric mucosal injury was induced by cold-restraint stress and two acupoints corresponding to Zusanli and Sanyinjiao in man were used. Methods: Cold-restraint stress produced typical gastric lesions in all rats of the stressed groups, but he number of ulcers as well as the mean ulcer diameter were reduced by 120 Hz EA pre-treatment. The cold-restraint stress also induced an increase in catecholamine response involving epinephrine, norepinephrine and dopamine, but an slight decline were observed in EA pre-treated rats compared with cold-restrained rats. Results: The degranulation value of gastric mast cell was significantly higher in cold-restrained rats than in control ones. However, with the significant reduction of degranulation values of gastric mast cells in EA pre-treated rats compared with cold-restrained ones, $PGE_2$ content in the gastric mucosa of EA pre-treated rats was also different from that observed in cold-restrained rats. Cold-restraint stress induced an elevated mRNA expression of pro-inflammatory gene such as cyclooxygenases-2 and tumor necrosis factor(TNF)-${\alpha}$, but these expression were down-regulated in EA pre-treated rats. Immunohistochemecal analysis showed that while the inhibitory-${\kappa}B{\alpha}$ an TNF-${\alpha}$ immunoreaction in the surface epithelium of the stomach tended to increase, both reactions in the EA pre-treated rats showed similar pattern as observed in controls. Conclusions : These results suggest that 120 Hz EA may act as a therapeutical means for gastric mucosal damages through a activation of pituitary adrenal system. it could be concluded that 120 hz high frequency electroacupuncture affords a good protective potential against stress-induce gastrointestinal dysfunction.

• International Journal of Concrete Structures and Materials
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• 제18권2E호
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• pp.73-77
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• 2006

This paper shows a study of the efficiency of expansive additive and shrinkage reducing admixture in controlling restrained shrinkage cracking of high performance concrete at early age. Free autogenous shrinkage test of $100{\times}100{\times}400mm$ concrete specimens and simulated completely-restrained test with VRTM(variable restraint testing machine) were performed. Creep and autogenous shrinkage of high-performance concrete with and without expansive additive and shrinkage reducing admixture were investigated by experiments that provided data on free autogenous shrinkage and restrained shrinkage. The results showed that the addition of expansive additive and shrinkage reducing admixture effectively reduced autogenous shrinkage and tensile stress in the restrained conditions. Also, it was found that the shrinkage stress was relaxed by 90% in high-performance concrete with and without expansive additive and shrinkage reducing admixtures at early age.

• Steel and Composite Structures
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• 제9권2호
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• pp.89-101
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• 2009

This paper presents a simplified model to study post-buckling behaviours of the axially restrained steel column at elevated temperatures in fire. The contribution of axial deformation to the curvature of column section is included in theoretical equations. The possible unloading at the convex side of the column when buckling occurs is considered in the stress-strain relationship of steel at elevated temperatures. Parameters that affect structural behaviours of the axial restrained column in fire are studied. The axial restraint cause an increase in the axial force before the column buckles; the buckling temperature of restrained columns will be lower than non-restrained steel columns. However, the axial force of a restrained column decreases after the column buckles with the elevation of temperatures, so make use of the post-buckling behaviour can increase the critical temperature of restrained columns. Columns with temperature gradient across the section will produce lower axial force at elevated temperatures.