• 문화기술의 융합
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• 제7권4호
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• pp.155-161
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• 2021

최근 소비 트렌드의 변화로 택배물량이 증가함에 따라 택배업 근로자의 산재사망 사고가 급증하여 택배근로자의 업무환경 개선이 시급한 실정이다. 따라서 본 연구의 목적은 택배근로자의 안전행동과 안전의식, 작업환경(물리적 환경, 직장내 안전문화, 안전체계), 직무스트레스(직무요구, 직무자율, 관계갈등, 기타요인) 간의 인과관계를 파악하여 안전행동을 높이기 위한 요인을 도출하고, 중점으로 관리되어야 하는 요인에 대한 기초자료를 제공하고자 함이다. 본 연구는 택배근로자 커뮤니티 사이트의 도움을 받아 물류센터에 종사하는 택배기사 총 119명을 대상으로 설문조사를 실시하였다. 타 연구의 설문조사 문항을 활용하여 제작한 안전행동, 안전의식, 작업환경, 직무스트레스 측정 도구를 사용하여 택배근로자의 근로특성에 맞는 문항으로 수정·보완한 설문지를 작성하였다. 교차분석 결과, 안전교육과 근속기간에 따른 사고 경험 여부에 대한 유의한 차이가 있었다. 또한 회귀분석 결과, 직무스트레스의 하위요인 중 관계갈등에 따른 안전행동, 작업환경의 하위요인 중 안전체계에 따른 안전행동에 대해 인과관계를 보였다. 피어슨의 상관분석 결과, 안전의식과 안전행동이 유의한 상관관계가 있었다. 이를 통해 사고 여부와 안전행동에 영향을 주는 요인을 알아내었고, 그에 대한 적절한 개선이 필요하다는 결론이 도출되었다.

• 한국산학기술학회논문지
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• 제19권12호
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• pp.294-302
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• 2018

간극수압을 받는 지반보의 응력-변형률 거동 분석을 위해 해석해와 유한요소해석결과를 정량적으로 상호 비교해 보았다. 유한요소해석을 통해 얻은 수평응력은 해석해에 의한 결과와는 달리 지반보의 수평축에 대하여 대칭성을 보이지 않았으나 요소의 개수가 증가함에 따라 대칭에 가까운 형태를 보였다. 해석해에 의한 수평응력을 유한요소의 가우스점에 대하여 얻은 수평응력과 비교해 볼 때 3개의 요소를 고려한 유한요소해석을 통해 얻은 인장응력의 값은 해석해에 의한 최대 인장응력값의 6% 였고 압축응력의 값은 해석해에 의한 최대값의 37% 였다. 6개의 요소를 고려한 유한요소해석을 통해 얻은 인장응력의 값은 해석해를 통해 얻은 최대값의 61% 였고 압축응력의 값은 해석해를 통해 얻은 최대값의 83% 였다. 지반보 내에 발생되는 연직응력은 해석해에 의할 경우 보의 깊이에 따라 연속적인 분포양상을 보인다. 유한요소해석에 의한 연직응력은 유한요소를 구성하는 요소에 따라 이산적인 분포를 보이는데 요소내의 4개의 가우스점에 대하여 얻은 평균 연직응력은 지반보에 작용하는 간극수압의 크기에 가까운 값을 보였다. 지반보의 중앙 근처에서의 연직변위량을 비교해 볼 때 3개의 요소로 구성된 지반보에 대한 유한요소해석을 통해 얻은 값은 해석해에 의한 값의 35% 였으며 6개의 요소로 구성된 지반보에 대한 유한요소해석을 통해 얻은 값은 해석해에 의한 값의 57% 였다.

• Structural Engineering and Mechanics
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• 제90권5호
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• pp.505-515
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• 2024

In this study, obtaining theoretical stress-strain curves and determining the parameters defining the equivalent rectangular stress block were aimed for 3 and 4-layered rectangular Reinforced Concrete (RC) cross-sections subjected to flexure. For these aims, the analytical stress-strain model proposed by Hognestad was chosen for the concrete grades (20 MPa≤fck≤60 MPa) used in this study. The tensile strength of the concrete was neglected and the thickness of the concrete layers in the compression zone of the concrete cross-section was taken as equal. In addition, while concrete strength was kept constant within each layer, concrete strengths belonging to separate layers were increased from the neutral axis towards the outer face of the compression zone of the concrete cross-section. After the equivalent rectangular stress block parameters were determined by numerical iterations, variations of these parameters depending on concrete strength in layers and layer numbers were obtained. Finally, some analytical equations have been proposed to predict the equivalent stress block parameters for the 3 and 4-layered RC cross-sections and validities of these proposed equations were shown by different metrics in this study.

• Structural Engineering and Mechanics
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• 제22권2호
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• pp.223-240
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• 2006

Taking into account the geometrical and material nonlinearities, an ultimate behavior of reinforced concrete cooling tower shell in hyperbolic configuration is presented. The design wind pressures suggested in the guidelines of the US (ACI) and Germany (VGB), with or without the effect of internal suction, are employed in the analysis to examine the qualitative and quantitative characteristics of each design wind pressure. The geometrical nonlinearity is incorporated by the Green-Lagrange strain tensor. The nonlinear features of concrete, such as the nonlinear stress-strain relation in compression, the tensile cracking with the smeared crack model, an effect of tension stiffening, are taken into account. The biaxial stress state in concrete is represented by an improved work-hardening plasticity model. From the perspective of quality of wind pressures, the two guidelines are determined as highly correlated each other. Through the extensive analysis on the Niederaussem cooling tower in Germany, not only the ultimate load is determined but also the mechanism of failure, distribution of cracks, damage processes, stress redistributions, and mean crack width are examined.

• 한국융합학회논문지
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• 제11권12호
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• pp.301-307
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• 2020

스트레스 인지와 구강증상경험의 관련성을 알아보기 위해 제 14차 청소년건강행태조사 자료를 이용하여 교차분석과 로지스틱회귀분석을 시행하였다. 전체 대상자의 81.7%는 평상 시 스트레스를 인지하고 있었고, 최근 12개월 동안 구강증상을 경험한 비율은 48.9%였다. 스트레스를 인지하는 그룹에서의 구강증상 경험률은 52.2%로, 인지하지 않는 그룹(34.0%) 보다 유의하게 높았고(p<0.001), 스트레스를 인지하지 않는 그룹에 비해 인지하는 그룹의 구강증상경험은 1.86배(95%CI: 1.78-1.95) 유의하게 높았다. 이는 청소년에서 스트레스와 구강증상경험이 유의한 관련이 있음을 시사한다. 향후 청소년들을 대상으로 한 구강보건교육 및 청소년들이 건강한 방법으로 스트레스를 해소할 수 있는 방안에 관한 연구가 필요하다.

• 한국안전학회지
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• 제2권3호
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• pp.5-11
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• 1987

In this study, a mild steel (SS41) of the carbon steel, a spring steel (SUP-9), and stainless steel (SUS 304) of the special gceel, etc, are adopted as the experimental materrials and are weded by $CO_2$(SS41, SUP-9), TIG (SUS304), respectively. And the residual stress distribution and fracture behavior at the welded zone are examined according to annealing temperatures of four section involving as welded. As a consequence, the best annealing temperatures that the residual stress is removed enough and mechanical properties are very suitable are at 90$0^{\circ}C$ (SS41), 75$0^{\circ}C$ (SUP-9), 110$0^{\circ}C$ (SUS 304), respectively.

• Ocean Systems Engineering
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• 제13권2호
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• pp.97-121
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• 2023

Through-the-thickness stress distribution in a tubular member has a profound effect on the fatigue behavior of tubular joints commonly found in steel offshore structures. This stress distribution can be characterized by the degree of bending (DoB). Although multi-planar joints are an intrinsic feature of offshore tubular structures and the multi-planarity usually has a considerable effect on the DoB values at the brace-to-chord intersection, few investigations have been reported on the DoB in multi-planar joints due to the complexity of the problem and high cost involved. In the present research, data extracted from the stress analysis of 243 finite element (FE) models, verified based on available parametric equations, was used to study the effects of geometrical parameters on the DoB values in two-planar tubular DYT-joints. Parametric FE study was followed by a set of nonlinear regression analyses to develop six new DoB parametric equations for the fatigue analysis and design of axially loaded two-planar DYT-joints.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1646-1652
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• 2006

A model of mechanical behavior of microcantilever due to intrinsic strain during deposition of MEMS structures is derived. A linear ordinary differential equation is derived for the beam deflection as a function of the thickness of the deposited layer. Closed-form solutions are not possible, but numerical solutions are plotted for various dimensionless ratios of the beam stiffness, the intrinsic strain, and the elastic moduli of the substrate and deposited layer. This model predicts the deflection of the cantilever as a function of the deposited layer thickness and the residual stress distribution during deposition. The usefulness of these equations is that they are indicative of the real time behavior of the structures, i.e. it predicts the deflection of the beam continuously during deposition process.

• Geomechanics and Engineering
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• 제21권2호
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• pp.103-109
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• 2020

The inflow rate is of interest in the design of underground structures such as tunnels and buried pipes below the groundwater table. Soil permeability governing the inflow rate significantly affects the hydro-geological behavior of soils but is difficult to estimate due to its wide range of distribution, nonlinearity and anisotropy. Volume changes induced by stress can cause nonlinear stress-strain behavior, resulting in corresponding permeability changes. In this paper, the nonlinearity and anisotropy of permeability are investigated by conducting Rowe cell tests, and a nonlinear permeability model considering anisotropy was proposed. Model modification and parameter evaluation for field application were also addressed. Significance of nonlinear permeability was illustrated by carrying out numerical analysis of a tunnel. It is highlighted that the effect of nonlinear permeability is significant in soils of which volume change is considerable, and particularly appears in the short-term flow behavior.

• Journal of Advanced Marine Engineering and Technology
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• 제22권6호
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• pp.800-808
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• 1998

In this study the thermal stress distribution and deformantion characteristics resulting from the nonuniform temperature fields of the cylinder block of a light 3-cylinder 4-stroke gasoline engine were analyzed using the 3-dimensional finite element method. The temperature distributions req-uisite for the thermoelastic behavior alalysis were obtained from the steady-state heat conduction analysis performed on the basis of experimental data. in order to examine the effect of a ceramic material the cylinder liner was replaced by the silicon nitride($Si_{3}N_{4}$) and its thermal behaviors were compared with those of the original block.