• 대한토목학회논문집
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• 제13권5호
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• pp.245-254
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• 1993

본 연구에서는 탄소봉을 이장한 모형실험, 극한해석 상계법, 그리고 극한평형법을 이용한 Meyerhof 방법을 통하여 편심량이 줄기초에 미치는 영향을 연구하였다. 극한해석 상계법에 적용된 파괴메카니즘은 모형실험에서 구하여 사용하였다. 세가지 방법에 의한 결과들을 분석한 결과, 모형실험과 극한해석 상계법에 의한 결과는 편심량에 상관없이 잘 일치하지만, Meyerhof 방법은 지지력을 보수적으로 평가하고, 편심량의 증가에 따른 지지력의 감소효과도 과소평가한다. 아울러 기초너비, 근입깊이, 바닥면의 마찰 등을 변화시켜 각 요소들이 지지력에 미치는 효과를 연구하였다.

• Steel and Composite Structures
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• 제16권1호
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• pp.97-114
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• 2014

This paper deals with a study on ultimate strength behaviour of eccentrically loaded CFT columns with and without shear connectors. Thirty specimens are subjected to experimental investigation under eccentric loading condition. P-M curves are generated for all the test specimens and critical eccentricities are evaluated. Three different D/t ratios such as 21, 25 and 29 and L/D ratios varying from 5 to 20 are considered as experimental parameters. Six specimens of bare steel tubes as reference specimens, twelve specimens of CFT columns without shear connectors and twelve specimens of CFT columns with shear connectors, in total thirty specimens are tested. The P-M values at the ultimate failure load of experimental study are found to be well agreed with the results of the proposed P-M interaction model. The load-deflection and load-strain behaviour of the experimental column specimens are presented. The behaviour of the CFT columns with and without shear connectors is compared. Experimental results indicate that the percentage increase in load carrying capacity of CFT columns with shear connectors compared to the ordinary CFT columns is found to be insignificant with a value ranging from 6% to 13%. However, the ductility factor of columns with shear connectors exhibit higher values than that of the CFT columns without shear connectors. This paper presents the proposed P-M interaction model and experimental results under varying parameters such as D/t and L/D ratios.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.306-311
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• 2003

A growing fatigue crack is known to be retarded on application of an overload cycle. The retardation may be characterized by the total number of cycles involved during retardation and the retarded crack length. The overload ratio plays an important role to influence the retardation behavior. The objective of the present investigation is to study the effect of different overload ratio on the retardation behavior. For DENT(double edge notched tension) specimens and ESET(eccentrically-loaded single edge crack tension) specimens, fatigue crack growth tests are conducted under cyclic constant-amplitude loading including a single tensile overloading with different overload ratios. The proposed crack retardation model predicts crack growth retardation due to a single tensile overloading. The predictions are put into comparison with the experimental results to confirm the reliability of this model.

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

• Structural Engineering and Mechanics
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• 제69권4호
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• pp.467-477
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• 2019

Digital image correlation (DIC) is now a popular and extensively used full-field metrology technique. In general, DIC is performed by using a turnkey solution offered by various manufacturers of DIC. In this paper, a simple and economical set-up for DIC is proposed which uses easily accessible digital single-lens reflex (DSLR) camera rather than industrial couple-charged device (CCD) cameras. The paper gives a description of aspects of carrying a DIC experiment which includes experimental set-up, specimen preparation, image acquisition and analysis. The details provided here will be helpful to carry DIC experiments without specialized DIC testing rig. To validate the responses obtained from proposed DIC set-up, tension and fatigue tests on specimens made of IS 2062 Gr. E300 steel are determined. Tensile parameters for a flat specimen and stress intensity factor for an eccentrically-loaded single edge notch tension specimen are evaluated from results of DIC experiment. Results obtained from proposed DIC experiments are compared with those obtained from conventional methods and are found to be in close agreement. It is also noted that the high resolution of DSLR allows the use of proposed approach for fracture characterization which could not be carried out with a typical turnkey DIC solution employing a camera of 2MP resolution.

• Steel and Composite Structures
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• 제45권1호
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• pp.23-38
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• 2022

This paper presents experimental and analytical studies of eccentrically loaded concrete-filled double steel (CFDST) and concrete-filled double skin tube (DCFST) columns having outer stainless steel tube. Eighteen CFDST and DCFST column specimens were manufactured and tested to examine the strength and load-deflection responses. In the study, the main parameters were concrete strength, load eccentricity, cross section and slenderness. The strengths, load-deflection diagrams and failure patterns of the columns were observed. In addition, the tested CFDST and DCFST columns were analyzed to attain the capacity and load versus lateral deflection responses. The obtained theoretical results were compared with the test results. A parametric study was also performed to research the effects of the ratio of eccentricity (e/H_o) slenderness ratio (L/r), H_o/t_o ratio, H_i/t_i ratio and the concrete compressive strength on the behavior of columns. In this work, the obtained results indicated that the ductility and capacity of columns were affected by cross section, concrete strength, steel strength, loading eccentricity and slenderness.

• 한국강구조학회 논문집
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• 제27권6호
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• pp.525-536
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• 2015

콘크리트피복 충전강관의 휨-압축 성능을 평가하기 위한 편심압축실험을 수행하였다. 기둥 주철근의 국부좌굴을 구속하고 콘크리트피복의 조기파괴를 방지하기 위하여 U형 띠철근 상세를 제안하였다. 주요 실험변수는 축하중 편심거리, 띠철근 간격, 그리고 콘크리트피복 여부이다. 실험결과 얇은 콘크리트피복에 수직균열이 조기에 발생하였지만 실험체의 최대강도는 콘크리트 피복의 기여도를 고려한 예측강도를 만족하였다. 또한, 내부 원형강관으로 인하여 제안된 콘크리트피복 충전강관은 우수한 변형능력을 나타냈다. 실험체의 휨-압축 강도 및 휨강성을 현행 설계기준과 비교하여 분석하였다.

• Steel and Composite Structures
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• 제22권4호
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• pp.797-820
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• 2016

This paper simulates the hysteretic behavior of steel reinforced recycled concrete (SRRC) columns under cyclic loads using OpenSees software. The effective fiber model and displacement-based beam-column element in OpenSees is applied to each SRRC columns. The Concrete01 material model for recycled aggregate concrete (RAC) and Steel02 material model is proposed to perform the numerical simulation of columns. The constitutive models of RAC, profile steel and rebars in columns were assigned to each fiber element. Based on the modelling method, the analytical models of SRRC columns are established. It shows that the calculated hysteresis loops of most SRRC columns agree well with the test curves. In addition, the parameter studies (i.e., strength grade of RAC, stirrups strength, steel strength and steel ratio) on seismic performance of SRRC columns were also investigated in detail by OpenSees. The calculation results of parameter analysis show that SRRC columns suffered from flexural failure has good seismic performance through the reasonable design. The ductility and bearing capacity of columns increases as the increasing magnitude of steel strength, steel ratio and stirrups strength. Although the bearing capacity of columns increases as the strength grade of RAC increases, the ductility and energy dissipation capacity decreases gradually. Based on the test and numerical results, the flexural failure mechanism of SRRC columns were analysed in detail. The computing theories of the normal section of bearing capacity for the eccentrically loaded columns were adopted to calculate the nominal bending strength of SRRC columns subjected to vertical axial force under lateral cyclic loads. The calculation formulas of horizontal bearing capacity for SRRC columns were proposed based on their nominal bending strength.

• 한국강구조학회 논문집
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• 제26권4호
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• pp.289-297
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• 2014

본 연구에서는 고강도강재(HSA800)의 단주 편심압축실험을 통해 휨-압축 부재의 강도를 평가하였다. 편심압축실험은 축력비에 따라 휨-압축의 조합력을 받는 부재의 P-M 상관관계를 알아보기 위해 HSA800강재의 각형강관과 H형강을 대상으로 실험을 수행하였으며, 가력 편심거리를 조정하여 다양한 P-M 조합에 대해 강도평가 실험을 수행하였다. 실험결과 실험최대 평균응력은 국부좌굴에 의한 최대내력이 결정된 실험체에 대해서는 판폭두께비가 증가함에 따라 감소하는 경향을 보였다. 발현강도의 여유는 축력이 낮을수록 상대적으로 휨강도에 대해 큰 마진을 보이고 있었고, 실험체 모두 현행 설계기준의 P-M 상관관계를 안전측으로 충족하였다.

• International Journal of Concrete Structures and Materials
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• 제11권1호
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• pp.135-149
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• 2017

The prediction of the actual ultimate capacity of confined concrete columns requires partial confinement utilization under eccentric loading. This is attributed to the reduction in compression zone compared to columns under pure axial compression. Modern codes and standards are introducing the need to perform extreme event analysis under static loads. There has been a number of studies that focused on the analysis and testing of concentric columns. On the other hand, the augmentation of compressive strength due to partial confinement has not been treated before. The higher eccentricity causes smaller confined concrete region in compression yielding smaller increase in strength of concrete. Accordingly, the ultimate eccentric confined strength is gradually reduced from the fully confined value $f_{cc}$ (at zero eccentricity) to the unconfined value $f^{\prime}_c$ (at infinite eccentricity) as a function of the ratio of compression area to total area of each eccentricity. This approach is used to implement an adaptive Mander model for analyzing eccentrically loaded columns. Generalization of the 3D moment of area approach is implemented based on proportional loading, fiber model and the secant stiffness approach, in an incremental-iterative numerical procedure to achieve the equilibrium path of $P-{\varepsilon}$ and $M-{\varphi}$ response up to failure. This numerical analysis is adapted to assess the confining effect in rectangular columns confined with conventional lateral steel. This analysis is validated against experimental data found in the literature showing good correlation to the partial confinement model while rendering the full confinement treatment unsafe.