• 한국자동차공학회논문집
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• 제6권5호
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• pp.1-9
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• 1998

The analysis concerns collapse behavior of framed vehicle models with the change of design parameters at the initial stage of conceptual design. Collapse analysis of a vehicle model with framed structures has been carried out using finite element limit analysis. The analysis makes sequential changes of design parameters from an initial model with frames of uniform section so as to stage then weak parts. As a result of those design changes, the collapse load of a model has been increased and the deflection toward a passenger room has been reduced. The results demonstrate the versatility of finite element limit analysis as a tool that confirms the safety of vehicle models.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.772-778
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• 2009

By rising the interests of the railroad, It has been required the research about railroad structure. And since 2000, the study about railway bridges caused by steel box railway bridges has been only 0.2%. So I was hard to find out about steel box railway bridges. In this study, I evaluate and analyze 4 types(KTX, Saemaeul, Mugunghwa, Freight) of dynamic caused by train loading, natural frequency and damping ratio, verticality deflection and verticality acceleration, end slope deflection, impact factor for dynamic characteristics analysis. natural frequency was measured 2.45Hz~3.34Hz and damping ratio revealed for 1.26~2.84%. Maximum verticality deflection(4.86mm) was sufficiently satisfied the design criteria(30.1mm), but in the case of verticality acceleration's respond, design criteria BRDM(Bridge Design Manual) & CTRL presentation derive rail limit value 0.35g be more than value 6 time recorded, maximum was measured 0.49g in 3 kinds of train(KTX, Saemaeul, Mugunghwa), except for Freight. Survey impact factor of Experiment bridge was 0.20 which is measured when the KTX(15:04) was driving. impact factor is enough contended with design criteria 0.29 which is presented in domestic railway design criteria and thoroughly guarantee the dynamic stability.

• 한국소음진동공학회논문집
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• 제19권12호
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• pp.1306-1314
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• 2009

By rising the interests of the railroad, It has been required the research about railroad structure. And since 2000, the study about railway bridges caused by steel box railway bridges has been only 0.2 %. So I was hard to find out about steel box railway bridges. In this study, I evaluate and analyze 4 types(KTX, Saemaeul, Mugunghwa, Freight) of dynamic caused by train loading, natural frequency and damping ratio, verticality deflection and verticality acceleration, end slope deflection, impact factor for dynamic characteristics analysis. natural frequency was measured 2.45 Hz~3.34 Hz and damping ratio revealed for 1.26~2.84 %. Maximum verticality deflection(4.86 mm) was sufficiently satisfied the design criteria(30.1 mm), but in the case of verticality acceleration's respond, design criteria BRDM(bridge design manual) & CTRL presentation derive rail limit value 0.35 g be more than value 6 time recorded, maximum was measured 0.49 g in 3 kinds of train(KTX, Saemaeul, Mugunghwa), except for Freight. Survey impact factor of Experiment bridge was 0.20 which is measured when the KTX(15:04) was driving. impact factor is enough contended with design criteria 0.29 which is presented in domestic railway design criteria and thoroughly guarantee the dynamic stability.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.723-738
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• 2014

Prestressing is the most commonly employed technique in bridges and long span beams in commercial buildings as prestressing results in slender section with higher load carrying capacities. This work is an attempt to study the performance of a minimum weight prestressed concrete beam adopting a non-prismatic section so that there will be a reduction in the volume of concrete which in turn reduces the self-weight of the structure. The effect of adopting a non-prismatic section on parameters like prestressing force, area of prestressing steel, bending stresses, shear stresses and percentage loss of prestress are established theoretically. The analysis of non-prismatic prestressed beams is based on the assumption of pure bending theory. Equations are derived for dead load bending moment, eccentricity, and depth at any required section. Based on these equations an algorithm is developed which does the stress checks for the given section for every 500 mm interval of the span. Limit state method is used for the design of beam and finite difference method is used for finding out the deflection of a non-prismatic beam. All the parameters of nonprismatic prestressed concrete beams are compared with that of the rectangular prestressed concrete members and observed that minimum weight design and economical design are not same. Minimum weight design results in the increase in required area of prestressing steel.

• 한국군사과학기술학회지
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• 제23권4호
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• pp.319-327
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• 2020

In this study a methodology to evaluate fatigue life of the electronic parts for the fighter radar unit under random vibration loading is presented. To do this, one parameter for the 3-σ RMS quation of Steinberg fatigue model is modified to come up with a printed circuit board(PCB) with multiple electronic parts, while fundamental frequency and dynamic deflection of the PCB are calculated from a MATLAB based finite element computer code. For the RIFA structure selected in this study, the 3-σ RMS fatigue limit displacement is reduced to 0.741 times as much as the Steinberg model. This investigation allows to assess the life of multiple electronic parts mounted on the PCB with reinforced metal cover/body showing non-sinusoidal deflection patterns.

• Structural Engineering and Mechanics
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• 제22권2호
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• pp.169-184
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• 2006

A close form solution of the maximum deflection for cracked columns with rectangular cross-sections was developed and thus the elastic buckling behavior and ultimate bearing capacity were studied analytically. First, taking into account the effect of the crack in the potential energy of elastic systems, a trigonometric series solution for the elastic deflection equation of an arbitrary crack position was derived by use of the Rayleigh-Ritz energy method and an analytical expression of the maximum deflection was obtained. By comparison with the rotational spring model (Okamura et al. 1969) and the equivalent stiffness method (Sinha et al. 2002), the advantages of the present solution are that there are few assumed conditions and the effect of axial compression on crack closure was considered. Second, based on the above solutions, the equilibrium paths of the elastic buckling were analytically described for cracked columns subjected to both axial and eccentric compressive load. Finally, as examples, the influence of crack depth, load eccentricity and column slenderness on the elastic buckling behavior was investigated in the case of a rectangular column with a single-edge crack. The relationship of the load capacity of the column with respect to crack depth and eccentricity or slenderness was also illustrated. The analytical and numerical results from the examples show that there are three kinds of collapse mechanisms for the various states of cracking, eccentricity and slenderness. These are the bifurcation for axial compression, the limit point instability for the condition of the deeper crack and lighter eccentricity and the fracture for higher eccentricity. As a result, the conception of critical transition eccentricity $(e/h)_c$, from limit-point buckling to fracture failure, was proposed and the critical values of $(e/h)_c$ were numerically determined for various eccentricities, crack depths and slenderness.

• 대한치과교정학회지
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• 제25권3호
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• pp.263-271
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• 1995

Canine retraction spring과 같은 looped wire에서, 각 변환요소에 따라 변하는 탄성 정도를 알아보기 위하여, wire의 재료, 굵기, loop에 소요된 길이, loop의 모양, gabling의 여부 등 5가지의 변환요소를 설정하여, 각 wire activation시의 탄성을 range, force, stiffness등의 면에서 알아보고자 하였다. wire의 재료적인 면에서 Hi-T (Unitek Co.)와 blue Elgiloy (Rocky Mountain Orthodontics)를 선택하였으며, 굵기로는 .016"$\;\times\;$.022" 와 .018"$\;\times\;$.025"를 선택하였다. loop 자체에 소요된 wire 길이를 15mm와 20mm의 두가지로, loop의 모양을 vertical open loop과 vertical closed loop의 두가지로, gabling의 양을 $0\circ$와 $30\circ$의 두가지로 하여 각각 제작하였다. 따라서 wire의 재료와 굵기, loop의 길이와 모양, gabling의 5가지 변환요소에 따라 32개군으로 구분되었으며, 각 군의 시료수는 8개씩으로, 총 256개의 시료를 대상으로 하였다. Instron(4202, Instron Co, USA)을 사용하여 각 시료의 하중변형 곡선을 얻었으며 elastic limit에서의 하중과 변형을 계측하고, 그때의 stiffness(force/range)를 산출하여, ANOVA 등의 통계처리로 32개군 간의 상관성을 조사하였다. 그 결과 wire의 재료, 굵기, loop의 길이, 모양, gabling모두가 looped wire의 하중 변형도에 유의한 영향을 미치는 것을 관찰할 수 있었으며, 탄성범위에서의 force는 Hi-T, .016"$\;\times\;$.022", loop 길이 20mm, open loop, non-gable군에서 가장 적었으며, blue Elgiloy, .018"$\;\times\;$.025", loop 길이 15mm, closed loop, non-gable군에서 가장 컸다. 탄성범위에서의 range는 Hi-T, .018"$\;\times\;$.025", loop길이 15mm, open loop, non-gable군이 가장 적었으며, Hi-T, .016"$\;\times\;$.022", loop길이 20mm, closed loop, gable군에서 가장 컸다. 또한 Looped wire의 탄성에 가장 큰 영향을 미치는 변환요소는 loop의 모양과 길이였으며, gabling의 영향이 가장 적었다.

• Steel and Composite Structures
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• 제24권3호
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• pp.369-382
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• 2017

This study investigates the reliability of the performance levels of moment resisting steel frames subjected to lateral loads such as wind and earthquake. The reliability assessment has been performed with respect to three performance levels: serviceability, damageability, and ultimate limit states. A four-story moment resisting frame is used as a typical example. In the reliability assessment the uncertainties in the loadings and in the capacity of the frame have been considered. The wind and earthquake loads are assumed to have lognormal distribution, and the frame resistance is assumed to have a normal distribution. In order to obtain an appropriate limit state function a linear relation between the loading and the deflection is formed. For the reliability analysis an algorithm has been developed for determination of limit state functions and iterations of the first order reliability method (FORM) procedure. By the method presented herein the multivariable analysis of a complicated reliability problem is reduced to an S-R problem. The procedure for iterations has been tested by a known problem for the purpose of avoiding convergence problems. The reliability indices for many cases have been obtained and also the effects of the coefficient of variation of load and resistance have been investigated.

• Journal of Biosystems Engineering
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• 제42권2호
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• pp.86-97
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• 2017

Purpose: This study aims to evaluate the applicability of a tractor-baler system equipped with a newly developed round baler by conducting stability analyses via static-state mathematical simulations and verification experiments for the tractor equipped with a loader. Methods: The centers of gravity of the tractor and baler were calculated to analyze the transverse overturning of the system. This overturning of the system was analyzed by applying mathematical equations presented in previous research and comparing the results with those obtained by the newly developed mathematical simulation. For the case of the tractor equipped with a loader, mathematical simulation results and experimental values from verification experiments were compared and verified. Results: The center of gravity of the system became lower after the baler was attached to the tractor and the angle of transverse overturning of the system steadily increased or decreased as the deflection angle increased or decreased between $0^{\circ}$ and $180^{\circ}$ on the same gradient. In the results of the simulations performed by applying mathematical equations from previous research, right transverse overturning occurred when the tilt angle was at least $19.5^{\circ}$ and the range of deflection angles was from $82^{\circ}$ to $262^{\circ}$ in counter clockwise. Additionally, left transverse overturning also occurred at tilt angles of at least $19.5^{\circ}$ and the range of deflection angles was from $259^{\circ}$ to $79^{\circ}$ in counter clockwise. Under the $0^{\circ}$ deflection angle condition, in simulations of the tractor equipped with a loader, transverse overturning occurred at $17.9^{\circ}$, which is a 2.3% change from the results of the verification experiment ($17.5^{\circ}$). The simulations applied the center of gravity and the correlations between the tilt angles, formed by individual wheel ground contact points excluding wheel radius and hinge point height, which cannot be easily measured, for the convenient use of mathematical equations. The results indicated that both left and right transverse overturning occurred at $19.5^{\circ}$. Conclusions: The transverse overturning stability evaluation of the system, conducted via mathematical equation modeling, was stable enough to replace the mathematical equations proposed by previous researchers. The verification experiments and their results indicated that the system is workable at $12^{\circ}$, which is the tolerance limit for agricultural machines on the sloped lands in South Korea, and $15^{\circ}$, which is the tolerance limit for agricultural machines on the sloped grasslands of hay in Japan.

• 한국철도학회논문집
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• 제20권1호
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• pp.111-119
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• 2017

이 연구에서는 자기부상열차-가이드웨이 상호작용을 고려하여 자기부상철도 가이드웨이 구조물의 진동사용성을 고려한 처짐한계를 제안한다. 간략화된 자기부상철도 시스템의 운동방정식을 유도하고, 자기부상력 제어를 위한 되먹임 상수가 부상공극의 변동량이 최소가 되도록 최적화한다. 이 시스템에 대하여 자기부상열차의 운행속도, 가이드웨이 경간장, 2차 현가장치의 고유진동수와 감쇠비를 변화시켜 가며, 부상공극의 크기와 차체의 연직가속도에 대한 사용성 기준을 만족하는 가이드웨이의 처짐한계를 조사한다. 해석 결과로부터 자기부상열차의 2차 현가장치에 대한 요구 조건과 가이드웨이 구조물이 만족시켜야 하는 처짐한계를 제안한다.