• Steel and Composite Structures
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• 제7권2호
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• pp.135-160
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• 2007

Recently, CFT column has been well-studied and reported on, because a CFT column has certain superior structural properties as well as good productivity, execution efficiency, and improved rigidity over existing columns. However, CFT column still has problems clearing the capacity evaluation between its steel tube member and high-strength concrete materials. Also, research on concrete has examined numerical values for high-strength concrete filled steel square tube columns (HCFT) to explain transformation performance (M-${\phi}$) when a short-column receives equal flexure-moment from axial stress. Moment-curvature formulas are proposed for HCFT columns based on analytic assumption described in this paper. This study investigated structural properties (capacity, curvature), through a series of experiments for HCFT with key parameters, such as strength of concrete mixed design (58.8 MPa), width-thickness ratio (D/t), buckling length to sectional width ratio (Lk/D) and concrete types (Zeolite, Fly-ash, Silica-fume) under eccentric loads. A comparative analysis executed for the AISC-LRFD, AIJ and Takanori Sato, etc. Design formulas to estimate the axial load (N)-moment (M)-curvature (${\phi}$) are proposed for HCFT columns based on tests results described in this paper.

• Steel and Composite Structures
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• 제47권3호
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• pp.437-450
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• 2023

A half open cross section built-up column, namely cold-formed thin-walled steel built-up column with 12-limbsection (CTSBC-12) is put forward. To deeply reveal the mechanical behaviors of CTSBC-12 under axial compression and put forward its calculation formula of axial bearing capacity, based on the previous axial compression experimental research, the finite element analysis (FEA) is conducted on 9 CTSBC-12 specimens, and then the variable parameter analysis is carried out. The results show the FEA is in good agreement with the experimental research, the ultimate bearing capacity error is within 10%. When the slenderness ratio is more than 96.54, the ultimate bearing capacity of CTSBC-12 decreases rapidly, and the failure mode changes from local buckling to global buckling. With the local buckling failure mode unchanged, the ultimate bearing capacity decreases gradually as the ratio of web height to thickness increases. Three methods are used for calculating the ultimate bearing capacity, the direct strength method of AISI S100-2007 gives result of ultimate axial load which is closest to the test and FEA results. But for simplicity and practicality, a simplified axial bearing capacity formula is proposed, which has better calculation accuracy with the slenderness ratio changing from 30 to 100.

• Structural Engineering and Mechanics
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• 제83권1호
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• pp.123-134
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• 2022

The stability of cable-stayed bridges is an important factor considered during design. In recent years, the novel spatial diamond-shaped bridge pylon has shown its advantages in various aspects, including the static response and the stability performance with the development of cable-stayed bridge towards long-span and heavy-load. Based on the energy approach, this paper presents a practical calculation method of the completed state stability of a cable-stayed bridge with two spatial diamond-shaped pylons. In the analysis, the possible transverse buckling of the girder, the top pylon column, and the mid pylon columns are considered simultaneously. The total potential energy of the spatial diamond-shaped pylon cable-stayed bridge is calculated. And based on the principle of stationary potential energy, the transverse buckling coefficients and corresponding buckling modes are obtained. Furthermore, an example is calculated using the design parameters of the Changtai Yangtze River Bridge, a 1176 m cable-stayed bridge under construction in China, to verify the effectiveness and accuracy of the proposed method in practical engineering. The critical loads and the buckling modes derived by the proposed method are in good agreement with the results of the finite element method. Finally, cable-stayed bridges varying pylon and girder stiffness ratios and pylon geometric dimensions are calculated to discuss the applicability and advantages of the proposed method. And a further discussion on the degrees of the polynomial functions when assuming buckling modes are presented.

• 대한기계학회논문집A
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• 제30권1호
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• pp.76-83
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• 2006

This paper addresses the method for the shape design sensitivity analysis of the buckling load in the continuous elastic body. The sensitivity formula for critical load is analytically derived and expressed in terms of shape variation, based on the continuum formulation of the stability problem. Though the buckling problem is more efficiently solved by the structural elements such as beam and shell, the elastic solids are considered in this paper because the solid elements can be used in general for any kind of structures whether they are thick or thin. The initial stress and buckling analysis is carried out by the commercial analysis code ANSYS. The sensitivity is computed by using the mathematical package MATLAB using the results of ANSYS. Several problems including straight and curved beams under compressive load, ring under pressure load, thin-walled section and bottle shaped column are chosen to illustrate the efficiency of the presented method.

• Steel and Composite Structures
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• 제4권3호
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• pp.211-226
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• 2004

This paper presents a study on the structural behaviour of modular steel scaffolds through both experimental and numerical investigations. Three one-storey and three two-storey modular steel scaffolds were built and tested to failure in order to examine the structural behaviour of typical modular steel scaffolds. Details of the tests and their test results were presented in this paper. Moreover, an advanced non-linear analysis method was employed to evaluate the load carrying capacities of these scaffolds under different support conditions. Comparisons between the experimental and the numerical results on the structural behaviour of these modular steel scaffolds were also presented. Moreover, the restraining effects of external supports in practical situations were also studied through finite element methods. The predicted load carrying capacities and deformations at failure of these models under partially restrained conditions were found to be close to the experimental results. A codified design method for column buckling with modified slenderness ratios was adopted for practical design of modular steel scaffolds.

• 한국강구조학회 논문집
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• 제21권5호
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• pp.505-514
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• 2009

본 논문에는 압측실험 결과에 근거한 원형강관의 구조적인 거동 및 설계강도에 대하여 기술하였다. 원형강관 기둥의 극한강도는 직경-두께비 및 세장비에 의하여 결정된다. 원형강관의 직경-두께비가 큰 경우 전체좌굴 발생 이전에 탄성 및 비탄성 국부좌굴이 일어나게 되어 기둥강도를 감소시키게 된다. 원형강관의 국부좌굴이 기둥강도에 미치는 영향을 연구하기 위하여 두께 2.8mm, 3.2 mm인 SM400 강판을 용접하여 직경-두께비 45에서 170까지인 원형강관을 제작하여 압축실험을 수행하였다. 실험결과에 따르면 직경-두께비가 현행 설계기준의 항복한계보다 작은 원형강관의 경우에도 비탄성국부좌굴이 발생하였으나 상당한 크기의 후좌굴강도를 보여 최대응력은 항복강도를 상회하였다. 도로교설계기준(2005)에 의한 허용응력은 실험결과와 비교하여 상당히 안전치로 나타났다. 최근에 개발된 직접강도법을 원형강관에 적용하기 위하여 실험 및 수치해석 결과와 비교한 결과, 제안된 직접강도법은 국부좌굴과 전체좌굴의 혼합 유무와 상관없이 원형강관 기둥의 극한강도를 적절하게 예측할 수 있는 것으로 나타났다.

• Steel and Composite Structures
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• 제43권3호
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• pp.341-351
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• 2022

This paper presents an inelastic buckling behavior analysis of rectangular hollow steel tubes with geometrical imperfections under elevated temperatures. The main variables are the temperature loads, slenderness ratios, and exposure conditions at high temperatures. The material and structural properties of steels at different temperatures are based on Eurocode (EN 1993-1-2, 2005). In the elastic buckling analysis, the buckling strength decreases linearly with the exposure conditions, whereas the inelastic buckling analysis shows that the buckling strength decreases in clusters based on the exposure conditions of strong and weak axes. The buckling shape of the rectangular steel column in the elastic buckling mode, which depicts geometrical imperfection, shows a shift in the position at which bending buckling occurs when the lower section of the member is exposed to high temperatures. Furthermore, lateral torsional buckling occurs owing to cross-section deformation when the strong axial plane of the model is exposed to high temperatures. The elastic buckling analysis indicates a conservative value when the model is exposed to a relatively low temperature, whereas the inelastic buckling analysis indicates a conservative value at a certain temperature or higher. The comparative results between the inelastic buckling analysis and Eurocode 3 show that a range exists in which the buckling strength in the design equation result is overestimated at elevated temperatures, and the shapes of the buckling curves are different.

• 한국강구조학회 논문집
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• 제10권2호통권35호
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• pp.253-261
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• 1998

보항복형 강구조골조가 지진하중을 받아 보 단부에 소성힌지가 생기는 종국상태에서는 최하층 기둥의 좌굴길이가 명확하게 되지 않는다. 이 연구의 목적은 그러한 경우의 콘크리트 충전 각형강관 기둥재의 내력을 조사하고 등가좌굴세장비를 제안하여 기둥재의 설계에 적용하고자 하는 것이다. 외부기둥들은 수평변위 탄성구속 스프링으로 모델화하였다. 그리고 수치해석으로 기둥재의 좌굴내력과 좌굴길이를 평가하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.733-740
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• 2006

Inverted V (or chevron) braced steel frames have been seen as being highly prone to soft story response once the compression brace buckles under earthquake loading. To salvage chevron braced frames. the concept of the zipper column was proposed many years ago such that the zipper column can redistribute the inelastic demand over the height of the building. However. rational design method for the zipper column has not been established yet. In this paper, a new dynamic design method for the zipper column was proposed by combining the refined physical braced model and modal pushover analysis. Inelastic dynamic analysis conducted on 6 story building model showed that the proposed method was more superior to the existing static design method and was very effective in improving seismic performance of chevron braced steel frames.

• Steel and Composite Structures
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• 제5권2_3호
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• pp.181-192
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• 2005

The effective length method for flexural (column) buckling has been used for many decades but its use is somewhat limited in various contemporary design codes to moderately slender structures with elastic critical load factor (${\lambda}_{cr}$) less than 3 to 5. In pace with the use of higher grade steel in recent years, the influence of buckling in axial buckling resistance of a column becomes more important and the over-simplified assumption of effective length factor can lead to an unsafe, an uneconomical or a both unsafe and uneconomical solution when some members are over-designed while key elements are under-designed. Effective length should not normally be taken as the distance between nodes multiplied by an arbitrary factor like 0.85, 1.0, 2.0 etc. Further, the classification of non-sway and sway-sensitive frames makes the conventional design procedure tedious to use and, more importantly, limited to simple regular frames. This paper describes the practical use of second-order analysis with section capacity check allowing for $P-{\delta}$ and $P-{\Delta}$ effects together with member and system imperfections. Most commercial software considers only the $P-{\Delta}$ effect, but not member and frame imperfections nor $P-{\delta}$ effect, and engineers must be very careful in their uses. A verification problem is also given for validation of software for this type of powerful second-order analysis and design. It is a trend for popular and advanced national design codes in using the second-order analysis as a norm for analysis and design of steel structures while linear analysis may only be used in very simple structures.