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Stability Analysis of Beck's Column with a Tip Mass Restrained by a Spring
李光范(Li, Guangfan),오상진(Oh, Sang-Jin),김권식(Kim, Gwon-Sik),이병구(Lee, Byoung-Koo) 한국소음진동공학회 2005 한국소음진동공학회 논문집 Vol.15 No.11
The purpose of this paper is to investigate free vibrations and critical loads of the Beck's columns with a tip spring, which carry a tip mass. The ordinary differential equation governing free vibrations of Beck's column subjected to a follower force is derived based on the Bernoulli-Euler beam theory Both the divergence and flutter critical loads are calculated from the load-frequency corves that are obtained by solving the differential equation numerically. The critical loads are presented in the figures as functions of various non-dimensional system parameters such as the subtangential parameter, mass ratio and spring parameter.
Elastica of Cantilever Column with Constant Volume Subjected to Combined Loads
이병구,이광범,윤희민,Lee, Byoung-Koo,Li, Guangfan,Yoon, Hee-Min Computational Structural Engineering Institute of 2007 한국전산구조공학회논문집 Vol.20 No.5
이 논문은 일정체적 캔틸레버 기둥의 정확탄성곡선(elastica)에 관한 연구이다. 기둥의 자유단에 압축하중과 모멘트 하중으로 구성되는 조합하중이 작용하는 캔틸레버 기둥의 정확탄성곡선을 지배하는 비선형 미분방정식과 경계조건을 유도하였다. 미분방정식에는 전단변형효과를 고려하였다. 기둥의 변단면으로는 정다각형 단면을 갖는 선형, 포물선형 및 정현의 변단면을 채택하였다. 기둥의 정확탄성곡선을 해석하기 위하여 유도된 미분방정식을 수치해석하였다. 수치해석의 결과를 이용하여 기둥의 무차원 변수들이 정확탄성곡선에 미치는 영향을 분석하였다. 실험실 규모의 실험을 실시하여 이 연구에서 얻어진 수치해석의 결과를 검증하였다. This paper deals with the elastica of deflected cantilever column with the constant volume. The columns are subjected to combined loads consisted of an axial compressive load and a couple moment at the free end. Differential equations governing the elastica of such column are derived, in which both the effects of taper type and shear deformation are included. Three kinds of taper types are considered: linear, parabolic and sinusoidal tapers. Differential equations are solved numerically to obtain the elastica of objective columns. The effects of various system parameters on the elastica are investigated extensively. Experimental studies were carried out in order to verify the theoretical results of non-linear behavior of the elasticas.
정진섭 ( Jeong Jin Seob ),이광범 ( Li Guangfan ),양재혁 ( Yang Jae Hyouk ) 한국농공학회 1999 한국농공학회 학술대회초록집 Vol.1999 No.-
The real strength envelope for soils without cementation goes through the origin and is curved. The Mohr-Coulomb failure criterion with the strength parameters c' and ø' from conventional tests overestimates the shear strength available at low normal stresses. The results of laboratory tests interpreted in terms of the Mohr-Coulomb failure criterion are not appropriate for evaluation of surficial slope stability, because the range of effective normal stresses in the field are not used in the laboratory tests.
이병구 ( Lee Byoung Koo ),이광범 ( Li Guangfan ),모정만 ( Mo Jeong Man ),신성철 ( Shin Sung Chul ) 한국농공학회 2000 韓國農工學會誌 : 전원과 자원 Vol.42 No.6
The purpose of this study is to investigate both the fundamental and some higher natural frequencies and mode shapes of compressive members resting on the linear elastic foundation. The model of compressive member is based on the classical Bernoulli-Euler beam theory. The differential equation governing free vibrations of such members subjected to an axial load is derived and solved numerically for calculating the natural frequencies and mode shapes. The Improved Euler method is used to integrate the differential equation and the Determinant Search method combined with the Regula-Falsi method to determine the natural frequencies, respectively. In numerical examples, the hinged-hinged, hinged-clamped, clamped-hinged and clamped-clamped end constraints are considered. The convergence analysis is conducted for determining the available step size in the Improved Euler method. The validation of theories developed herein is also conducted by comparing the numerical results between this study and SAP 90. The non-dimensional frequency parameters are presented as the non-dimensional system parameters: section ratio, modulus parameter and load parameter. Also typical mode shapes are presented.
이병구(Lee, Byoung-Koo),이광범(Li, Guang-Fan),강희종(Kang, Hee-Jong),윤희민(Yoon, Hee-Min) 한국소음진동공학회 2007 한국소음진동공학회 논문집 Vol.17 No.9
This paper deals with the flexural free vibrations of circular strip foundation with the variable breadth on Pasternak soil. The breadth of strip varies with the linear functional fashion, which is symmetric about the mid-arc. Differential equations governing flexural free vibrations of such strip foundation are derived, in which the elastic soil with the shear layer, i.e. Pasternak soil, is considered. Effects of the rotatory and shear deformation are included in the governing equations. Differential equations are numerically solved to calculate the natural frequencies and mode shapes. In the numerical examples, the hinged-hinged, hinged-clamped and clamped-clamped end constraints are considered. Four lowest frequency parameters accompanied with their corresponding mode shapes are reported and parametric studies between frequency parameters and various system parameters are investigated.
정진섭 ( Jeong Jin Seob ),이대재 ( Lee Dae Jae ),이광범 ( Li Guang Fan ) 한국농공학회 2000 한국농공학회 학술대회초록집 Vol.2000 No.-
A wide range of problems geotechnical engineering have been analyzed by using the finite element method. In order to establish confidence in a numerical procedure, it is desirable that numerical solution be verified against field or laboratory observations, or both, and in order to aid the user in applying the method to practical problems, it is necessary to examine effects of various parameters that influence the behavior of engineering structures. Often it can be profitable to translate numerical solutions in formats that can be used readily for design analysis. The allowable bearing capacity of concrete piles is mainly governed by settlement rather than by strength of soil. Therefore, the load-displacement behavior of piles should be well understood at the design stage. This paper deals with some of these goals by considering the problem of load-displacement behavior of axially-loaded pile foundations.
정진섭,이광범,최두헌 圓光大學校 環境建設硏究所 1999 環境建設論文集 Vol.8 No.-
In this parer, the results of an experimental study on Samangeum dredged sand are presented. Undrained cyclic triaxial compression tests were performed on Saemangeum dredged sand to evaluate factors affecting liquefaction strength and liquefaction behavior characteristics. The results of these tests show that cyclic liquefaction can occur not only very loose sand(relative density is 30%) but also dense sand(relative density is 70%). To evaluate effect of the over consolidation ratio on the liquefaction strength, a series of undrained cyclic triaxial compression test was performed, and the result of this test showed that the liquefaction strength of saemangeum dredged sand approximately increased to square root of over consolidation ratio in the range of OCR value of 1.0 to 4.0. In the anisotropically consolidated sample tests, the liquefaction strength is increased by increasing the effective consolidation ratio.