• Structural Engineering and Mechanics
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• 제49권2호
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• pp.273-283
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• 2014

According to deformation features of pre-twisted bar, its elastic bending and torsion buckling equation is developed in the paper. The equation indicates that the bending buckling deformations in two main bending directions are coupled with each other, bending and twist buckling deformations are coupled with each other as well. However, for pre-twisted bar with dual-axis symmetry cross-section, bending buckling deformations are independent to the twist buckling deformation. The research indicates that the elastic torsion buckling load is not related to the pre-twisted angle, and equals to the torsion buckling load of the straight bar. Finite element analysis to pre-twisted bar with different pre-twisted angle is performed, the prediction shows that the assumption of a plane elastic bending buckling deformation curve proposed in previous literature (Shadnam and Abbasnia 2002) may not be accurate, and the curve deviates more from a plane with increasing of the pre-twisting angle. Finally, the parameters analysis is carried out to obtain the relationships between elastic bending buckling critical capacity, the effect of different pre-twisted angles and bending rigidity ratios are studied. The numerical results show that the existence of the pre-twisted angle leads to "resistance" effect of the stronger axis on buckling deformation, and enhances the elastic bending buckling critical capacity. It is noted that the "resistance" is getting stronger and the elastic buckling capacity is higher as the cross section bending rigidity ratio increases.

• Geomechanics and Engineering
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• 제14권6호
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• pp.589-600
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• 2018

For foundations in permafrost regions, the displacement characteristics are uncertain because of the randomness of temperature characteristics and mechanical parameters, which make the structural system have an unexpected deviation and unpredictability. It will affect the safety of design and construction. In this paper, we consider the randomness of temperature characteristics and mechanical parameters. A stochastic analysis model for the uncertain displacement characteristic of foundations is presented, and the stochastic coupling program is compiled by Matrix Laboratory (MATLAB) software. The stochastic displacement fields of an embankment in a permafrost region are obtained and analyzed by Neumann stochastic finite element method (NSFEM). The results provide a new way to predict the deformation characteristics of foundations in permafrost regions, and it shows that the stochastic temperature has a different influence on the stochastic lateral displacement and vertical displacement. Construction disturbance and climate warming lead to three different stages for the mean settlement of characteristic points. For the stochastic settlement characteristic, the standard deviation increases with time, which imply that the results of conventional deterministic analysis may be far from the true value. These results can improve our understanding of the stochastic deformation fields of embankments and provide a theoretical basis for engineering reliability analysis and design in permafrost regions.

• 한국지반공학회지:지반
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• 제9권1호
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• pp.21-30
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• 1993

본 연구에서는 지반해석을 위한 여러 방법중 유한요소법에 의한 연성해석 및 역해석기법을 이용하여, 지반변형해석과 토질정수의 추정방법 등에 대하여 연구하였다. 토질정수의 정확한 산정의 필요성을 알기 위하여, 지반의 탄성해석에서의 탄성계수, 투수계수, 포아송비 등에 따른 민감도를 분석 고찰하였고, 여러가지의 점토질 흙에 대한 압밀실험결과를 이용하여 역해석기법에 의한 토질정수의 산정을 실시하고, 이 토질정수를 이용한 탄성해석에 의하여 지반의 변형과 간극수압을 구하여, 다음과 같은 결과를 얻었다. 탄성해석에 있어서, 지반의 탄성계수에 따른 지반변형량과 간극수압의 민감도가 비교적 크게 나타나므로, 탄성계수의 산정은 매우 중요하며, 재하하중이 클수록 탄성계수의 산정을 정확히 하여야 한다. 작은 하중단계에서의 짧은 시간의 실측치를 이용한 역해석을 통하여 토질정수를 산정함으로 4, 비교적 단순한 탄성해석을 통하여서도, 더욱 큰 하중 재하시 또 장기간의 변형량을 실제와 가잠게 예측할 수 있으며, 역해석에서의 반복계산 회수를 줄이고 더욱 좋은 결과를 얻기 위해서는, 초기치 실측 절점의 개수를 증가시키고 초기 실측치의 더욱 정확한 산정이 필요하다.

• 대한토목학회논문집
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• 제13권4호
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• pp.39-49
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• 1993

전단변형(剪斷變形) 효과(效果)가 고려되는 공간(空間)뼈대 구조(構造)의 기하학적(幾何學的)인 비선형(非線形) 해석(解析)을 수행하기 위한 두 가지 방법 즉, 유한분절법(有限分節法)과 유한요소법(有限要素法)을 제시한다. 유한분절법(有限分節法)의 경우에는 평형방정식(平衡方程式)을 직접(直接) 적분(積分)하므로써 휨과 비틂거동(擧動)에 대한 엄밀(嚴密)한 접선강도(接線剛度) 매트릭스가 유도되는 반면에 유한요소법(有限要素法)의 경우에는 전단변형(剪斷變形)을 고려하는 Hermitian 다항식(多項式)을 형상함수(形狀函數)로 사용하므로써 탄성(彈性) 및 기하적(幾何的)인 강도(剛度)매트릭스가 산정된다. 또한 축방향력(軸方向力)이 영(零)인 경우에 휨 및 비틂거동으로 인한 부재양단의 길이변화를 보정하는 Bowing 함수와 불평형하중의 산정방법을 제시한다. 선택된 예제(例題)들을 해석(解析)한 결과들과 다른 문헌(文獻)의 결과들을 비교, 검토하므로써 본(本) 논문(論文)에서 제시된 이론(理論)의 정당성(正當性)을 입증(立證)한다.

• Earthquakes and Structures
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• 제13권5호
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• pp.485-496
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• 2017

The behavior of 8 steel reinforced high-strength concrete (SRHSC) columns, which comprised of four identical columns with cross-shaped steel and other four identical columns with square steel tube, was investigated experimentally under cyclic uniaxial and biaxial loading independently. The influence of steel configuration and loading path on the global behavior of SRHSC columns in terms of failure process, hysteretic characteristics, stiffness degradation and ductility were investigated and discussed, as well as stress level of the longitudinal and transverse reinforcing bars and steel. The research results indicate that with a same steel ratio deformation capacity of steel reinforced concrete columns with a square steel tube is better than the one with a cross-shaped steel. Loading path affects hysteretic characteristics of the specimens significantly. Under asymmetrical loading path, hysteretic characteristics of the specimens are also asymmetry. Compared with specimens under unidirectional loading, specimens subjected to bidirectional loading have poor carrying capacity, fast stiffness degradation, small yielding displacement, poor ductility and small ultimate failure drift. It also demonstrates that loading paths affect the deformation capacity or deformation performance significantly. Longitudinal reinforcement yielding occurs before the peak load is attained, while steel yielding occurs at the peak load. During later displacement loading, strain of longitudinal and transverse reinforcing bars and steel of specimens under biaxial loading increased faster than those of specimens subjected to unidirectional loading. Therefore, the bidirectional loading path has great influence on the seismic performance such as carrying capacity and deformation performance, which should be paid more attentions in structure design.

• Steel and Composite Structures
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• 제39권1호
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• pp.51-64
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• 2021

This paper presents a high-order shear and normal deformation theory for the bending of FGM plates. The number of unknowns and governing equations of the present theory is reduced, and hence makes it simple to use. Unlike any other theory, the number of unknown functions involved in displacement field is only four, as against five or more in the case of other shear and normal deformation theories. Based on the novel shear and normal deformation theory, the position of neutral surface is determined and the governing equilibrium equations based on neutral surface are derived. There is no stretching-bending coupling effect in the neutral surface-based formulation, and consequently, the governing equations of functionally graded plates based on neutral surface have the simple forms as those of isotropic plates. Navier-type analytical solution is obtained for functionally graded plate subjected to transverse load for simply supported boundary conditions. The accuracy of the present theory is verified by comparing the obtained results with other quasi-3D higher-order theories reported in the literature. Other numerical examples are also presented to show the influences of the volume fraction distribution, geometrical parameters and power law index on the bending responses of the FGM plates are studied.

• 콘크리트학회논문집
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• 제20권1호
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• pp.3-11
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• 2008

현재 국내에서 건설되고 있는 대부분의 아파트는 철근콘크리트 전단벽과 바닥슬래브만으로 구성된 순수벽식구조 형태를 이용하고 있다. 이러한 벽식 구조 아파트에 대한 리모델링시 개구부 설치는 필연적이며 개구부 설치치 벽체의 거동은 매우 복잡하며, 연결부재인 보와 슬래브 같은 부재에 많은 영향을 받는다. 본 연구에서는 개구부가 있는 전단벽에 대해 횡하중 실험을 실시하였다. 실험체는 1980년대에 지어진 벽식 구조아파트를 대상으로 1/2축소 실험체를 제작하였다. 개구부의 면적 및 연결 슬래브의 위험단면은 기존 연구를 참고하여 결정하였다. 실험 결과 개구부 설치에 따른 내력 감소가 나타났으며, 연결 슬래브의 응력은 전단면에 대하여 균일하게 작용하지 않았다. 전단벽체와 커플링 작용을 하는 슬래브의 유효폭 및 위험단면은 기존 연구와 비교하여 큰 차이점을 나타냈으며, 국내의 아파트에 적용하기에는 다소 과소평가되고 있는 것으로 나타났다.

• 한국항공우주학회지
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• 제41권1호
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• pp.1-9
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• 2013

이 논문에서는 2 차원 실린더의 와류유발진동에 따른 Lock-in 현상에 대해 수치해석을 수행하였다. 실린더의 운동을 모사하기 위해 변형격자와 고정격자를 이용하였다. 스프링 상사기법을 이용하여 격자를 변형하였다. 격자수 및 시간 간격 등을 조절해 얻은 수렴된 수치해가 비교 및 검증에 사용되었다. 또한, 유체-구조 결합 방법들의 효율성과 정확도를 비교 검토하였다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.266-271
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• 2009

A modeling method for the modal analysis of a multi-packet blade system having a crack undergoing rotational motion is presented in this paper. Each blade is assumed as a slender cantilever beam. The stiffness coupling effects between blades due to the flexibilities of the disc and the shroud are modeled with discrete springs. Hybrid deformation variables are employed to derive the equations of motion. The flexibility due to crack, which is assumed to be open during the vibration, is calculated basing on a fracture mechanics theory. To obtain more general information, the equations of motion are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters related to the angular speed, the depth and location of a crack on the modal characteristics of the system are investigated with some numerical examples.

• Structural Engineering and Mechanics
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• 제52권4호
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• pp.787-813
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• 2014

Starting with Hamilton's variational principle, the governing field equations for the steady state response of thin-walled beams under harmonic forces are derived. The formulation captures shear deformation effects due to bending and warping, translational and rotary inertia effects and as well as torsional flexural coupling effects due to the cross section mono-symmetry. The equations of motion consist of four coupled differential equations in the unknown displacement field variables. A general closed form solution is then developed for the coupled system of equations. The solution is subsequently used to develop a family of shape functions which exactly satisfy the homogeneous form of the governing field equations. A super-convergent finite element is then formulated based on the exact shape functions. Key features of the element developed include its ability to (a) isolate the steady state response component of the response to make the solution amenable to fatigue design, (b) capture coupling effects arising as a result of section mono-symmetry, (c) eliminate spatial discretization arising in commonly used finite elements, (d) avoiding shear locking phenomena, and (e) eliminate the need for time discretization. The results based on the present solution are found to be in excellent agreement with those based on finite element solutions at a small fraction of the computational and modelling cost involved.