• Computational Structural Engineering
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• v.6 no.1
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• pp.91-98
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• 1993

Minimum weight design of the boom of an excavator with stress and displacement constraints was performed. The procedure of analysis consists of the following steps. The finite element model of the boom was built up by using 227 triangular plate elements each of which has three nodes. And then the finite element program was implemented and its accuracy was verified by comparing its results with those of the commercial structural analysis package-ANSYS 4.4A. For the constraints of stresses and displacements, the design sensitivities of those were computed using direct differentiation method. To verify the reliability of them the results were compared with those of the finite difference method. The optimum design value was obtained by using PLBA(Pshenichny-Lim-Belegundu-Arora)non-linear optimization program which adopts the active set strategy. Using the above results, minimum weight design of an excavator boom showed an effect of 27% reduction in weight.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.3
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• pp.24-30
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• 1998

Strength and displacement of jig body in index machine utilized for multiprocess machining such as drilling, boring and tapping, etc, at the same time were analyzed by the use of finite element analysis soft ware ANSYS 5.2A. The whole geometry was constructed by 4048 elements and 7016 nodes employing 8 node brick element. The analyses were carried out on five loading cases combining vertical and horizontal machining to simulate the case occurring large displacement and the one occurring small displacement one and provided following conclusions. (1) Jig body had sufficient strength because its safety factor was 6.95 even in the most severe loading case. (2) The largest displacement in Z direction was 549 m and that in radial direction was 43.7 m. (3) In order to reduce the displacement, vertical machining rather than horizontal or two or three processes should be adopted in the same station. (4) Alternate change of horizontal machining direction at consecutive stations can reduce the displace ment. (5) The dimension of the slider should be increased to reduce the displacement by the tolerance in the sliding part. (6) A bypass idle piston head needs to be installed to give a counterpart supporting load from opposite direction for a single horizontal machining case.

• Journal of Korean Association for Spatial Structures
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• v.3 no.1 s.7
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• pp.87-97
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• 2003

The structural system that discreterized from continuous shells is frequently used to make a large space structures. As well these structures show the unstable phenomena when a load level over the limit load, and snap-through and bifurcation are most well known of it. For the collapse mechanism, rise-span ratio, element stiffness and load mode are main factor, which it give an effect to unstable behavior. In our real situation, most structures have semi-rigid joint that has middle characteristic between pin and rigid joint. So the knowledge of semi-rigid joint is very important problem of stable large space structure. And the instability phenemena of framed space structures show a strong non-linearity and very sensitive behavior according to the joint rigidity For this reason In this study, we are investigating to unstable problem of framed structure with semi-rigidity and to grasp the nonlinear instability behavior that make the fundamental collapse mechanism of the large space frame structures with semi-rigid joint, by proposed the numerical analysis method. Using the incremental stiffness matrix in chapter 2, we study instability of space structures.

• Journal of Korean Society of Steel Construction
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• v.17 no.4 s.77
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• pp.385-394
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• 2005

In this paper, a discrete optimum design program was developed using the refined fuzzy-genetic algorithms based on the genetic algorithms and the fuzzy theory. The optimum design in this study can perform section and shape optimization simultaneously for planar and spatial steel structures. In this paper, the objective function is the weight of steel structures and the constraints are the design limits defined by the design and buckling strengths, displacements, and thicknesses of the member sections. The design variables are the dimensions and coordinates of the steel sections. Design examples are given to show the applicability of the discrete optimum design using the improved fuzzy-genetic algorithms in this study.

• Land and Housing Review
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• v.12 no.4
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• pp.119-125
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• 2021

The study presents the ductility reinforcement effect of the RC bending member using the CFRP Grid as an experimental result. Experimental variables include a non-reinforced RC bending member (ORI), a bottom reinforced RC bending member (REB), and an RC bending member reinforced at the bottom and side (REBS). The experiment was carried out with four points bending test. As a result of the experiment, it was confirmed that the maximum bending strength increased by 17-20% through reinforcement. In addition, the ductility index calculation results confirmed that the ductility index of REB and REBS increased by 2 and 3 times, respectively, compared to the ORI.

• Journal of Korean Society of Steel Construction
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• v.11 no.4 s.41
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• pp.417-424
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• 1999

In this paper a nonlinear analysis of three-dimensional steel frames is developed. This analysis accounts for material and geometric nonlinearities. The material nonlinearity includes gradual yielding associated with flexural behaviors. The geometric nonlinearity includes the second-order effects associated with $P-{\delta}\;and\;P-{\Delta}$ effects. The material nonlinearity at the node is considered using the concept of P-M hinge consisting of many fibers. The geometric nonlinearity is considered by the use of stability function. The nonlinearity caused by shear and torsional interaction effects is neglected. The modified incremental displacement method is used as the solution technique. The load-displacements predicted by the proposed analysis compare well with those given by other approaches.

• Journal of Korea Water Resources Association
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• v.49 no.9
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• pp.773-787
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• 2016

A coupled river-overland hydrodynamic model was applied to estimate flood risk by a scenario-based approach. The study area is Seongseo Industrial Complex in Daegu which is located near Nakdong river and Geumho river. Inundation depth and velocity at each time were calculated by applying a coupled 1D/2D hydrodynamic model to the target area of interest. The 2D inundation analysis for river and overland domain was performed with the scenario-based approach that there are levee overflow against 100/200 year high quantile (97.5%) design flood and levee break against 100/200 year normal quantile (50%) design flood. The level of flood risk was displayed for resident/industrial area using information about maximum depth and velocity of each node computed from the 2D inundation map. The research outcome would be very useful in establishing specified emergency action plans (EAP) in case of levee break and overflowing resulting from a flood.

• Proceedings of the Korea Water Resources Association Conference
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• 2023.05a
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• pp.512-512
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• 2023

내성천은 대한민국의 대표적인 모래하천으로서 흰수마자(Gobiobotia naktongensis)의 최적 서식처로 알려져 있다. 흰수마자는 낙동강에서 채집되어 새로운 종으로 보고된 한국 고유종이지만 최근 멸종위기야생생물 I급 담수어류로 지정되었다. 흰수마자는 입자가 1 mm 이하의 가는 모래로 90% 이상 구성된 모래하상과 수질이 양호한 곳에서 서식하는 것으로 알려져 있다(Kim et al, 2014). 특히 낙동강 중류의 감천과 상류의 내성천 수계에서 비교적 많은 개체수가 출현하고 있는 것으로 보고되었다(Na et al., 2015). 그러나 영주댐 건설 이후, 댐 하류 내성천에서 흰수마자의 개체수가 급격히 줄어들었다. 2021년 내성천 유역 자연성생태계모니터링 보고서(환경부, 2022)에 따르면 내성천에서 흰수마자가 2016년에 492개체가 채집된 이후 2019년 7월엔 1개체만이 채집되었으며 이후 2022년 8월까지 채집되지 않았다. 반면 망둥어과 어류 중 입자가 굵은 하상환경에서 주로 서식하는 밀어의 개체수는 증가하는 경향을 보였다. 이는 내성천 유역의 하상환경변화가 어류서식에 직간접적으로 영향을 미친것으로 해석할 수 있다. 본 연구는 물리서식처 모형인 River2D를 활용하여 내성천 석탑교(No. 46) 에서 회룡교(No. 4)까지 약 40 km 구간을 대상으로 2010년 하상 입자와 2020년 하상 입자 크기에 따른 흰수마자의 서식처 적합도 변동양상을 분석하였다. River2D 모형을 통해 계산되는 어류 서식처 적합도는 물리서식처 모의시스템에서 사용되는 가중가용면적(WUA: Weighted Usable Area)에 근거하여 산출된다. WUA는 대성어종의 특정 성장단계별, 서식처 특성별로 주어진 구간을 이용할 수 있는 순수적합도(net suitability)에 대한 하나의 지표이다. WUA가 크다는 것은 그만큼 대상어종의 서식처 및 활동 영역이 크다는 것을 의미한다. WUA는 각 절점에서 평가되어지는 복합서식처 적합도 지수에 의해 계산된다. 본 연구에서는 곱셈방법을 적용한 복합 서식처 적합도 지수를 산정하여 하상입자에 따른 흰수마자의 서식처 적합도 변동양상을 분석하였다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.3 no.4
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• pp.109-122
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• 1983

An accurate thick beam element (TB4) which includes the effects of the shear deformation and rotatory inertia has been degenerated from the three dimensional continuum by employing the Timoshenko beam assumptions. The proposed TB4 element has four nodes and two degrees of freedom at each node, totally eight degrees of freedom. The transverse deflection W and plane rotation ${\theta}$ with the cubic interpolation functions are selected as nodal variables. The element characteristics are formulated by discretizing the beam equations of motion, using the Galerkin weighted residual method, and are numerically integrated by the reduced shear integration technique, using the three-point Gauss quadrature with the various shear coefficients. Several numerical examples are analyzed to demonstrate the accuracy and the monotonic convergence behavior of the proposed TB4 beam element. The result indicates that the TB4 element shows the more excellent performance and the monotonic convergence behavior than the other existing Timoshenko beam type elements for the whole range of the beam aspect ratios, in both static and free vibration analyses.

• Journal of the Korea Concrete Institute
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• v.17 no.5 s.89
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• pp.761-768
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• 2005

Lately outmoded and functionally obsolete buildings constructed in 1960s and 1970s are often remodelled and restored. Even though there are not serious structural defects in the existing buildings, many old buildings have been reconstructed to improve residence quality or to extend residence area of the buildings. The experimental or theoretical research on plane expansion of RC apartments is quite scare. In this research, 12 specimens and 19 RC slabs connected by hinged joints were tested. The new slab was connected to the existing slab by hinge joints injecting dowel bars between two slabs. Main parameters of the slabs are types of the dowel bars (D13 and D19), spacing of the dowel bars (150mm, 300mm, and 450mm), and the locations of the steel bars in the existing slabs. The test results indicated that the shear strength of the RC test slabs having various types of dowel bars was about twice that calculated by the ACI 318-02 code. All slabs failed in concrete spatting and the dowel steel bars did not reach their yield strengths.