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저 품위 철광석을 사용한 식생용 투수 콘크리트의 중성화 및 제작에 관한 연구
은희창,이민수,배충열 강원대학교 산업기술연구소 2007 産業技術硏究 Vol.27 No.A
Recently produced concrete has a tendency to overcome environmental defects. Porous and planting Eco-concrete requires the neutralization process and enough void in concrete to contain water, to pass air freely, and provides necessary nutrients to vegetation roots. The biological environment in concrete is not suitable for planting because the concrete possesses strong alkali constituent of pH 11-13. This study evaluated the strength and serviceability of concrete as well as the chemical characteristics of concrete mixed by low-grade iron ore left in the abandoned mine and treated by Ammonium monohydrogen phosphate, (NH_(4))_(2)HPO_(4). Test variables include two kinds of coarse aggregates such as crushed stones and low-grade iron ore, the duration time and the period for neutralization treatment by Ammonium monohydrogen phosphate, (NH_(4))_(2)HPO_(4), and the proportion ratio of cement, blast furnace slag and silica fume.
On Shear Capacity of Reinforced Concrete Deep Beamswith Rectangular Web Openings
은희창,양근혁,이영호,정헌수 대한건축학회 2005 Architectural research Vol.7 No.2
Based on an experimental study, this study provides an equation to describe the shear strength of high-strength concrete deep beams with rectangular openings and without web reinforcements. Twenty-four concrete deep beams were tested with the variables of concrete strength, size of web opening, and shear span-to-depth ratio. The proposed equation is expressed as the sum of the shear strength provided by longitudinal bars and concrete. It is illustrated that the proposed equation predicts the load-carrying capacity of the deep beams more properly than the experimental equations proposed by other researchers.
Constrained Dynamic Responses of Structures Subjected to Earthquake
은희창,이민수 대한건축학회 2006 Architectural research Vol.8 No.2
Starting from the quadratic optimal control algorithm, this study obtains the relation of the performance index for constrained systems and Gausss principle. And minimizing a function of the variation in kinetic energy at constrained and unconstrained states with respect to the velocity variation, the dynamic equation is derived and it is shown that the result compares with the generalized inverse method proposed by Udwadia and Kalaba. It is investigated that the responses of a 10-story building are constrained by the installation of a two-bar structure as an application to utilize the derived equations. The structural responses are affected by various factors like the length of each bar, damping, stiffness of the bar structure, and the junction positions of two structures. Under an assumption that the bars have the same mass density, this study determines the junction positions to minimize the total dynamic responses of the structure.
Analytical Method for Constrained Mechanical and Structural Systems
은희창,박상렬,이은택,정헌수 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.10
The objective of this study is to present an accurate and simple method to describe the motion of constrained mechanical or structural systems. The proposed method is an elimination method to require less effort in computing Moore-Penrose inverse matrix than the generalized inverse method provided by Udwadia and Kalaba. Considering that the results by numerical integration of the derived second-order differential equation to describe constrained motion veer away the constrained trajectories, this study presents a numerical integration scheme to obtain more accurate results. Applications of holonomically or nonholonomically constrained systems illustrate the validity and effectiveness of the proposed method.
An Analytical Approach for Structural Synthesis of Substructures
은희창,박상렬,이은택 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.9
A structure is broken down into a number of substructures by means of the finite element method and the substructures are synthesized for the complete structure. The divided substructures take two types: fixed-free and free-free elements. The flexibility and stiffness matrices of the free-free elements are the Moore-Penrose inverse of each other. Thus, it is not easy to determine the equilibrium equations of the complete structure composed of two mixed types of substructures. This study provides the general form of equilibrium equation of the entire structure through the process of assembling the equilibrium equations of substructures with end conditions of mixed types. Applications demonstrate that the proposed method is effective in the structural analysis of geometrically complicated structures.
Structural and Mechanical Systems Subjected to Constraints
은희창,이은택,정헌수,박상렬 대한기계학회 2004 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.18 No.11
The characteristics of dynamic systems subjected to multiple linear constraints are determined by considering the constrained effects. Although there have been many researches to investigate the dynamic characteristics of constrained systems, most of them depend on numerical analysis like Lagrange multipliers method. In 1992, Udwadia and Kalaba presented an explicit form to describe the motion for constrained discrete systems. Starting from the method, this study determines the dynamic characteristics of the systems to have positive semidefinite mass matrix and the continuous systems. And this study presents a closed form to calculate frequency response matrix for constrained systems subjected to harmonic forces. The proposed methods that do not depend on any numerical schemes take more generalized forms than other research results.
구속조건을 고려한 일반화된 해밀턴의 운동방정식 ( Generalized Hamiltonian considering constraints )
은희창,이영인,정헌수 대한건축학회 1998 大韓建築學會論文集 : 構造系 Vol.14 No.8
Lagrange 역학으로부터 해밀턴의 운동방정식이 유도된다. 그러나 주어진 시스템 이 임의의 구속조건이 부여될 경우에는 해밀턴에 의한 일반화된 운동방정식을 유도하기란 상당한 어려움이 있다. 특히 구속조건이 nonholonomic일 경우에는 그 방법이 매우 복잡하거나 어려운 점이 있다. 따라서 본 연구에서는 해밀턴 역 학을 근거로 구속된 시스템의 운동을 묘사하는 방법을 제시한다. 이 방법은 기존 의 다른 방법과는 달리 주어진 조건식을 시간에 관해 미분만을 취하여 이를 지 배방정식에 대입함으로써 보다 용이하고 간단히 접근할 수 있는 장점이 있으며, 예제를 통하여 그 결과의 타당성을 입증한다. 그러나 해밀턴의 역학은 가상일 법 에 그 근거를 두고 있는 바 명백한 시간의 함수를 갖는 구속조건은 좀처럼 적용 하기 어렵다. 또한 Chetaev 형태의 구속조건이외의 nonholonomic 구속조건일 경 우에는 모멘타의 정의를 수정해야 하는 등의 복잡한 문제점들이 있으므로 이에 대한 연구들은 향후에 고려되어야 할 것이다.