• 국제강구조저널
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• 제18권4호
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• pp.1440-1463
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• 2018

The Wagner coefficient is a key parameter used to describe the inelastic lateral-torsional buckling (LTB) behaviour of the I-beam, since even for a doubly-symmetric I-section with residual stress, it becomes a monosymmetric I-section due to the characteristics of the non-symmetrical distribution of plastic regions. However, so far no theoretical derivation on the energy equation and Wagner's coefficient have been presented due to the limitation of Vlasov's buckling theory. In order to simplify the nonlinear analysis and calculation, this paper presents a simplified mechanical model and an analytical solution for doubly-symmetric I-beams under pure bending, in which residual stresses and yielding are taken into account. According to the plate-beam theory proposed by the lead author, the energy equation for the inelastic LTB of an I-beam is derived in detail, using only the Euler-Bernoulli beam model and the Kirchhoff-plate model. In this derivation, the concept of the instantaneous shear centre is used and its position can be determined naturally by the condition that the coefficient of the cross-term in the strain energy should be zero; formulae for both the critical moment and the corresponding critical beam length are proposed based upon the analytical buckling equation. An analytical formula of the Wagner coefficient is obtained and the validity of Wagner hypothesis is reconfirmed. Finally, the accuracy of the analytical solution is verified by a FEM solution based upon a bi-modulus model of I-beams. It is found that the critical moments given by the analytical solution almost is identical to those given by Trahair's formulae, and hence the analytical solution can be used as a benchmark to verify the results obtained by other numerical algorithms for inelastic LTB behaviour.

• Steel and Composite Structures
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• 제34권5호
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• pp.643-655
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• 2020

In the present work, the buckling behavior of a single-layered graphene sheet (SLGS) embedded in visco-Pasternak's medium is studied using nonlocal four-unknown integral model. This model has a displacement field with integral terms which includes the effect of transverse shear deformation without using shear correction factors. The visco-Pasternak's medium is introduced by considering the damping effect to the classical foundation model which modeled by the linear Winkler's coefficient and Pasternak's (shear) foundation coefficient. The SLGS under consideration is subjected to compressive in- plane edge loads per unit length. The influences of many parameters such as nonlocal parameter, geometric ratio, the visco-Pasternak's coefficients, damping parameter, and mode numbers on the buckling response of the SLGSs are studied and discussed.

• Advances in nano research
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• 제15권2호
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• pp.175-189
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• 2023

The under-evaluation structure includes a functionally graded porous (FGP) core which is confined by two piezoelectric carbon nanotubes reinforced composite (CNTRC) layers. The whole structure rests on the Pasternak foundation. Using quasi-3D hyperbolic shear deformation theory, governing equations of a sandwich plate are driven. Moreover, face sheets are subjected to the electric field and the whole model is under thermal loading. The properties of all layers alter continuously along with thickness direction due to the CNTs and pores distributions. By conducting the current study, the results emerged in detail to assess the effects of different parameters on buckling of structure. As instance, it is revealed that highest and lowest critical buckling load and consequently stiffness, is due to the V-A and A-V CNTs dispersion type, respectively. Furthermore, it is revealed that by porosity coefficient enhancement, critical buckling load and consequently, stiffness reduces dramatically. Current paper results can be used in various high-tech industries as aerospace factories.

• Steel and Composite Structures
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• 제27권1호
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• pp.75-87
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• 2018

This paper presents a new method to compute the shear strength of composited structural B-C-W members. These B-C-W members, defined as concrete-filled steel box beams, columns and shear walls, consist of a slender rectangular steel plate box filled with concrete and inserted steel plates connecting the two long-side steel plates. These structural elements are intended to be used in structural members of super-tall buildings and nuclear safety-related structures. The concrete confined by the steel plate acts to be in a multi-axial stressed state: therefore, its shear strength was calculated on the basis of a concrete's failure criterion model. The shear strength of the steel plates on the long sides of the structural element was computed using the von Mises plastic strength theory without taking into account the buckling of the steel plate. The spacing and strength of the inserted plates to induce plate yielding before buckling was determined using elastic plate theory. Therefore, a predictive method to compute the shear strength of composited structural B-C-W members without considering the shear span ratio was obtained. A coefficient considering the influence of the shear span ratio was introduced into the formula to compute the anti-lateral bearing capacity of composited structural B-C-W members. Comparisons were made between the numerical results and the test results along with this method to predict the anti-lateral bearing capacity of concrete-filled steel box walls. Nonlinear static analysis of concrete-filled steel box walls was also conducted by using ABAQUS and the results agreed well with the experimental data.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 1999년도 추계학술대회논문집
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• pp.265-272
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• 1999

This stability of a plate structure is very crucial problem which results in wrinkle and bucking. In this study, the effect of the pattern of spot-welding points of the two rectangular plates on the compressive and shear bucking load is studied with respect to the thickness, aspect ratio of plates and number of welding spots. Buckling coefficient of the plate not welded was compared with that of two plates with various thickness to extract the effect of thickness. The effect of number of welding spots are studied in two directions, longitudinal and transverse directions. The conclusions obtained were that the reinforcement effect was maximized when the aspect ratio was close to 1.75 at compressive load condition and that the effect of number of welding spots in transverse direction was larger than that in longitudinal direction at shearing load condition.

• Geomechanics and Engineering
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• 제32권2호
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• pp.159-177
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• 2023

In the present work, a simple and refined shear deformation theory is used to analyze the effect of visco-elastic foundation on the buckling response of exponentially-gradient sandwich plates under various boundary conditions. The proposed theory includes indeterminate integral variables kinematic with only four generalized parameters, in which no shear correction factor is used. The visco-Pasternak's foundation is taken into account by adding the influence of damping to the usual foundation model which characterized by the linear Winkler's modulus and Pasternak's foundation modulus. The four governing equations for FGM sandwich plates are derived by employing principle of virtual work. To solve the buckling problem, Galerkin's approach is utilized for FGM sandwich plates for various boundary conditions. The analytical solutions for critical buckling loads of several types of powerly graded sandwich plates resting on visco-Pasternak foundations under various boundary conditions are presented. Some numerical results are presented to indicate the effects of inhomogeneity parameter, elastic foundation type, and damping coefficient of the foundation, on the critical buckling loads.

• Earthquakes and Structures
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• 제22권6호
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• pp.539-548
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• 2022

Steel plate shear walls (SPSWs) are one of the most important and widely used lateral load-bearing systems. The reason for this is easier execution than reinforced concrete (RC) shear walls, faster construction time, and lower final weight of the structure. However, the main drawback of SPSWs is premature buckling in low drift ratios, which affects the energy absorption capacity and global performance of the system. To address this problem, two groups of SPSWs under cyclic loading were investigated using the finite element method (FEM). In the first group, several series of circular rings have been used and in the second group, a new type of SPSW with concentric circular rings (CCRs) has been introduced. Numerous parameters include in yield stress of steel plate wall materials, steel panel thickness, and ring width were considered in nonlinear static analysis. At first, a three-dimensional (3D) numerical model was validated using three sets of laboratory SPSWs and the difference in results between numerical models and experimental specimens was less than 5% in all cases. The results of numerical models revealed that the full SPSW undergoes shear buckling at a drift ratio of 0.2% and its hysteresis behavior has a pinching in the middle part of load-drift ratio curve. Whereas, in the two categories of proposed SPSWs, the hysteresis behavior is complete and stable, and in most cases no capacity degradation of up to 6% drift ratio has been observed. Also, in most numerical models, the tangential stiffness remains almost constant in each cycle. Finally, for the innovative SPSW, a relationship was suggested to determine the shear capacity of the proposed steel wall relative to the wall slenderness coefficient.

• Structural Engineering and Mechanics
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• 제46권2호
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• pp.269-294
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• 2013

This paper is concerned with the determination of exact buckling loads and vibration frequencies of variable thickness isotropic plates using well known finite difference technique. The plates are subjected to uni, biaxial compression and shear loadings and various combinations of boundary conditions are considered. The buckling load is found out as the in plane load that makes the determinant of the stiffness matrix equal to zero and the natural frequencies are found out by carrying out eigenvalue analysis of stiffness and mass matrices. New and exact results are given for many cases and the results are in close agreement with the published results. In this paper, like finite element method, finite difference method is applied in a very simple manner and the application of boundary conditions is also automatic.

• Structural Engineering and Mechanics
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• 제91권4호
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• pp.383-391
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• 2024

Conical shell is a common engineering structure, which is widely used in machinery, civil and construction fields. Most of them are usually exposed to external environments, temperature is an important factor affecting its performance. If the external temperature is too high, the deformation of the conical shell will occur, leading to a decrease in stability. Therefore, studying the thermal-post buckling behavior of conical shells is of great significance. This article takes graphene platelets reinforced metal foams (GPLRMF) conical shells as the research object, and uses high-order shear deformation theory (HSDT) to study the thermal post-buckling behaviors. Based on general variational principle, the governing equation of a GPLRMF conical shell is deduced, and discretized and solved by Galerkin method to obtain the critical buckling temperature and thermal post-buckling response of conical shells under various influencing factors. Finally, the effects of cone angles, GPLs distribution types, GPLs mass fraction, porosity distribution types and porosity coefficient on the thermal post-buckling behaviors of conical shells are analyzed in detail. The results show that the cone angle has a significant impact on the nonlinear thermal stability of the conical shells.

• 한국강구조학회 논문집
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• 제27권5호
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• pp.455-470
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• 2015

본 연구에서는 국내에서 생산되어 사용되고 있는 원형 파형강판을 대상으로 전단 및 휨 강도를 보다 정확하게 산정하기 위한 방안을 제시하고자 하였다. 국내 설계기준 및 기존 연구에 대한 비교 분석을 통하여 기존식에 대한 한계를 분석하고, 실험 및 비선형 해석을 통하여 원형 파형강판에 대한 좌굴강도 설계식을 제안하였다. 본 연구에서 제안한 전단좌굴 감소계수와 한계 판폭두께비를 이용하여 실험 및 해석결과와 비교한 결과, 상당히 유사한 거동을 나타내었다. 본 연구의 결과는 원형 파형강판의 부재 설계 및 구조성능평가에 편리하게 적용될 수 있을 것으로 판단된다.