• Structural Engineering and Mechanics
• /
• 제73권1호
• /
• pp.17-25
• /
• 2020

A finite element (FE) model for analyzing slender reinforced high-strength concrete (HSC) columns under biaxial eccentric loading is formulated in terms of the Euler-Bernoulli theory. The cross section of columns is divided into discrete concrete and reinforcing steel fibers so as to account for varied material properties over the section. The interaction between axial and bending fields is introduced in the FE formulation so as to take the large-displacement or P-delta effects into consideration. The proposed model aims to be simple, user-friendly, and capable of simulating the full-range inelastic behavior of reinforced HSC slender columns. The nonlinear model is calibrated against the experimental data for slender column specimens available in the technical literature. By using the proposed model, a numerical study is carried out on pin-ended slender HSC square columns under axial compression and biaxial bending, with investigation variables including the load eccentricity and eccentricity angle. The calibrated model is expected to provide a valuable tool for more efficiently designing HSC columns.

• Interaction and multiscale mechanics
• /
• 제5권2호
• /
• pp.91-104
• /
• 2012

There is relatively little numerical study on the behavior of eccentrically loaded high strength rectangular concrete-filled steel tubular (CFST) slender beam-columns with large depth-to-thickness ratios, which may undergo local and global buckling. This paper presents a multiscale numerical model for simulating the interaction local and global buckling behavior of high strength thin-walled rectangular CFST slender beam-columns under eccentric loading. The effects of progressive local buckling are taken into account in the mesoscale model based on fiber element formulations. Computational algorithms based on the M$\ddot{u}$ller's method are developed to obtain complete load-deflection responses of CFST slender beam-columns at the macroscale level. Performance indices are proposed to quantify the performance of CFST slender beam-columns. The accuracy of the multiscale numerical model is examined by comparisons of computer solutions with existing experimental results. The numerical model is utilized to investigate the effects of concrete compressive strength, depth-to-thickness ratio, loading eccentricity ratio and column slenderness ratio on the performance indices. The multiscale numerical model is shown to be accurate and efficient for predicting the interaction buckling behavior of high strength thin-walled CFST slender beam-columns.

• Environmental Analysis Health and Toxicology
• /
• 제26권
• /
• pp.5.1-5.11
• /
• 2011

Objectives: In order to identify the possibility of slender bitterling (SB) (Acheilognathus yamatsutae) being used as a test species for estrogenic endocrine disrupting chemicals (EEDCs), we carried out the cloning and sequence characterization of the estrogen receptor (ER). Methods: The ER from a slender bitterling was obtained by reverse transcriptase-polymerase chain reaction (RT-PCR), 5'- and 3'-rapid amplification of cDNA ends (5'-RACE and 3'-RACE) and T-vector cloning. The expression of ER mRNA was also analyzed in six tissues (brain, liver, kidney, gill, gonad, and intestines) by real-time PCR. Results: We obtained an ER from the slender bitterling. The SB ER cDNA was 2189 base pairs (bp) in length and contained a 1707 bp open reading frame that encoded 568 amino acid residues. The SB ER amino acid sequence clustered in a monophyletic group with the $ER{\alpha}$ of other fish, and was more closely related to zebrafish $ER{\alpha}$(88% identity) than to the $ER{\alpha}$ of other fish. The SB ER cDNA was divided into A/B, C, D, E and F domains. The SB ER has conserved important sequences for ER functions, such as the DNA binding domain (D domain), which are consistent with those of other teleosts. Conclusions: The ER of the slender bitterling could provide basic information in toxicological studies of EEDCs in the slender bitterling.

• 수산해양기술연구
• /
• 제27권1호
• /
• pp.83-90
• /
• 1991

현존하는 세장선 이론과는 아주 다르게 Kelvin 소오스와 그의 궤적 주위에 대한 점근전개를 행하여 전진 운동을 하는 세장체에 대한 공식을 유도하였다. 여기서 발전된 공식은 기본적으로 Neumann-Kelvin 문제의 Kernel함수에 대한 근사와 동등하게되었다. 경계치 문제는 현저하게 단순화되었으며 해는 선수 끝에서 시작하는 축차적분의 진행 절차에 따라 얻어졌다. 속도장과 압력분포는 2차원 속도 포텐시열의 미분에 의해 간단히 계산될 수 있었다. 이 방법은 비록 컴퓨터의 사용에는 Neumann-Kelvin문제처럼 많은 시간이 필요하게 되더라도 선체 주위의 유동장의 수치해석에 더욱 정확하리라는 가능성을 준다. 전진하는 진동 세장체의 문제에도 같은 방법이 유용하리라는 것을 또한 기대한다.

• 한국정밀공학회지
• /
• 제32권5호
• /
• pp.471-481
• /
• 2015

This paper presents the robot vision control schemes using Extended Kalman Filter (EKF) method for the slender bar placement in the appearance of obstacles during robot movement. The vision system model used for this study involves the six camera parameters($C_1{\sim}C_6$). In order to develop the robot vision control scheme, first, the six parameters are estimated. Then, based on the estimated parameters, the robot's joint angles are estimated for the slender bar placement. Especially, robot trajectory caused by obstacles is divided into three obstacle regions, which are beginning region, middle region and near target region. Finally, the effects of number of obstacles using the proposed robot's vision control schemes are investigated in each obstacle region by performing experiments of the slender bar placement.

• Steel and Composite Structures
• /
• 제37권5호
• /
• pp.533-549
• /
• 2020

Recently, Concrete-filled double skin steel tubular (CFDST) columns have proven an exceptional structural resistance in terms of strength, stiffness, and ductility. However, the resistance of these column members can be severely affected by the type of loading in which bending stresses increase in direct proportion with axial load and eccentricity value. This paper presents a non-linear finite element based modeling approach that studies the behavior of slender CFDST columns under biaxial loading. Finite element models were calibrated based on the outcomes of experimental work done by other researchers. Results from simulations of slender CFDST columns under axial loading eccentric in one direction showed good agreement with the experimental response. The calibrated models are expanded to a total of thirty models that studies the behavior of slender CFDST columns under combined compression and biaxial bending. The influences of parameters that are usually found in practice are taken into consideration in this paper, namely, eccentricity-to-diameter (e/D) ratios, slenderness ratios, diameter-to-thickness (D/t) ratios, and steel contribution ratios. Finally, an analytical study based on current code provisions is conducted. It is concluded that South African national standards (2011) provided the most accurate results contrasted with the Eurocode 4 (2004) and American Institute of Steel Construction (2016) that are found to be conservative. Accordingly, correction factors are proposed to the current design guidelines to provide more satisfactory results.

• Steel and Composite Structures
• /
• 제6권4호
• /
• pp.285-302
• /
• 2006

This paper describes the design and behaviour of cold-formed stainless steel slender circular hollow section columns. The columns were compressed between fixed ends at different column lengths. The investigation focused on large diameter-to-plate thickness (D/t) ratio ranged from 100 to 200. An accurate finite element model has been developed. The initial local and overall geometric imperfections have been included in the finite element model. The material nonlinearity of the cold-formed stainless steel sections was incorporated in the model. The column strengths, load-shortening curves as well as failure modes were predicted using the finite element model. The nonlinear finite element model was verified against test results. An extensive parametric study was carried out to study the effects of cross-section geometries on the strength and behaviour of stainless steel slender circular hollow section columns with large D/t ratio. The column strengths predicted from the parametric study were compared with the design strengths calculated using the American Specification, Australian/New Zealand Standard and European Code for cold-formed stainless steel structures. It is shown that the design strengths obtained using the Australian/New Zealand and European specifications are generally unconservative for the cold-formed stainless steel slender circular hollow section columns, while the American Specification is generally quite conservative. Therefore, design equation was proposed in this study.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
• /
• pp.275-282
• /
• 2001

In this paper, nonlinear analyses of RC (Reinforced Concrete) columns are conducted, and an improved criterion to estimate the design load carrying capacity of slender RC columns is proposed. To simulate the material nonlinearty including the cracking of concrete, the layer model is adopted, and the initial stress matrix is considered for the simulation of P- effect. After correlation studies with previous numerical results to verify the efficiency of the developed numerical model, many parameter studies are followed, and a regression formula which can give more exact resisting capacity of slender RC columns is introduced on the basis of the obtained numerical results.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2000년도 춘계 학술발표회 논문집 Proceedings of EESK Conference-Spring
• /
• pp.202-212
• /
• 2000

This study investigates the ductility capacity of slender-wide reinforced concrete walls under predominant flexural moment loading. The experimental work for this study aims to provide design guidelines for bar detailing in critical regions under compressive stress in particular in case of slender-wide RC walls. According to the experimental observation the Bernoulli hypothesis of linear strain distribution is no longer valid and the ultimate compressive strain of concrete is significantly reduced, It is postulated that the nonlinear strain distribution causes the concentrated compressive stressed region and hence the premature crushing failure at the toe of walls. The reduced ultimate strain and nonlinear strain distribution need transverse reinforcement for confinement and more realistic models for the strength and displacement estimation of slender-wide RC wall.

• 한국지진공학회:학술대회논문집
• /
• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
• /
• pp.448-454
• /
• 2000

Piled multi-block system has been frequently adopted in the historic structures or monuments of cultural heritage. It is well known that such a structural system is very vulnerable to the earthquake shaking. If the structure is of slender type, then it may experience overturning at very low level intensity of ground shaking. One of the methods used to protect such structures from earthquake is seismic isolation system. But the behavior of multi-block systems mounted on the isolated basis is not well understood yet. In this paper we investigate the dynamic behavior of single slender rigid block mounted on the three different isolation systems, i.e., P-F system, FPS and LRB system. Sliding at the isolation interface of P-F system and FPS is formulated based on Coulomb friction. The mounted single block is assumed undergoing rocking or sticking only. Impacting of a single block is described using distinct element method (DEM). Free vibrations due to a prescribed initial conditions are studied. Responses to the harmonic excitation and earthquake motions are calculated