본 논문에서는 좌굴에 취약한 철도판형교의 전체좌굴 거동특성을 검토하였다. 우선 철도판형교의 전체좌굴에 영향을 미치는 영향인자를 파악하고 좌굴을 유발하는 모멘트를 전체좌굴에 대한 무차원좌굴계수 를 적용하여 이론적으로 산정하였 다. 다음으로는 개단면인 철도판형교의 하부를 브레이싱으로 보강한 단면을 보강단면과 등가인 두께를 가지는 얇은 판으로 치환하여 유사폐합단면을 형성하고 보강 형상별로 국부적인 항복 발생 여부를 검토한 후, 전체좌굴을 유발하는 모멘트를 산정 하고 효율적인 보강상세를 결정하였다. 유한요소 해석을 이용하여 표준열차하중이 재하되었을 때 보강모델별로 철도판형교에 발생하는 횡방향 변위를 비교하여 장대레일의 좌굴에 저항하기 위한 최적의 보강상세를 제안하였다.

In the case of a school building, even though it is a regular structure in terms of plan shape, if the masonry infill wall acts as a lateral load resisting element, it can be determined as a torsionally irregular building. As a result, the strength and ductility of the structure are reduced, which may cause additional earthquake damage to the structure. Therefore, in this study, a structure similar to a school building with torsional irregularity was selected as an example structure and the damping performance of the PC-BRB was analyzed by adjusting the eccentricity according to the amount of masonry infilled wall. As a result of nonlinear dynamic analysis after seismic reinforcement, the torsional irregularity of each floor was reduced compared to before reinforcement, and the beams and column members of the collapse level satisfied the performance level due to the reduction of shear force and the reinforcement of stiffness. The energy dissipation of PC-BRB was similar in the REC-10 ~ REC-20 analytical models with an eccentricity of 20% or less. REC-25 with an eccentricity of 25% was the largest, and it is judged that it is effective to combine and apply PC-BRB when it has an eccentricity of 25% or more to control the torsional behavior.

Buckling Restrained Braces can not only express the strength considered at the time of design, but also reduce the seismic load by energy dissipation according to the plastic behavior after yield deformation of the steel core. The physical characteristics and damping effect may be different according to the buckling prevention method of the steel core by the lateral restraint element. Accordingly, in this study, To compare hysteresis characteristics, Specimen(BRB-C) filled with mortar, specimen(BRB-R) combined with a buckling restraint ring and Specimen(BRB-EP) filled with engineering plastics was fabricated, and a cyclic loading test was performed. As a result of the cyclic loading test, the maximum compressive strength, cumulative energy dissipation and ductility of each test specimen was similar. But in case of the cumulative energy dissipation and ductility, BRB-C filled with the mortar specimen showed the lowest. This is considered to be because the gap between the steel core and the reinforcing material for plastic deformation was not uniformly formed by pouring mortar around the core part.

Namnabat et al. (cf., [Carbon Letters, https://doi.org/10.1007/s42823-020-00194-2]) employ the classical approach of Li and Chou (cf., [Int J Solids Struct 40: 2487–2499]) to the implementation of the molecular structural mechanics method using the Bernoulli–Euler beam elements for nonlinear buckling analysis of double-layered graphene nanoribbons. However, more recent studies by Eberhardt and Wallmersperger (cf., [Carbon 95: 166–180]) and others (see, e.g., [Int J Eng Sci 133: 109–131]) have shown that the classical approach of Li and Chou poorly reproduces both in-plane and out-of-plane mechanical moduli of graphene. We have shown that the 2D beam-based hexagonal material used by Namnabat et al. poorly simulates the mechanical moduli of graphene, especially the bending rigidity modulus, and this material cannot be used for the buckling simulation of graphene sheets (or nanoribbons). In addition, it is noted that in Int J Eng Sci 133: 109–131, a modification of the classical approach of Li and Chou is given which exactly reproduces both in-plane (2D Young’s modulus and Poisson’s ratio) and out-of-plane (bending rigidity modulus) mechanical moduli of graphene using beam elements.

Double-layer graphene nanoribbons promise potential application in nanoelectromechanical systems and optoelectronic devices, and knowledge about mechanical stability is a crucial parameter to flourish the application of these materials at the next generation of nanodevices. In this paper, molecular mechanics is utilized to investigate nonlinear buckling behavior, critical buckling stress, and lateral deflection of double-layered graphene nanoribbons under various configurations of stacking mode and chirality. The implicit arc-length iterative method (modified Riks method) with Ramm’s algorithm is utilized to analyze the nonlinear structural stability problem. The covalent bonds are modeled using three-dimensional beam elements in which elastic moduli are calculated based on molecular structural mechanics technique, and the interlayer van der Waals (vdW) interactions are modeled with nonlinear truss elements. An analytical expression for Young’s modulus of nonlinear truss elements is derived based on the Lennard–Jones potential function and implemented in numerical simulation with a UMAT subroutine based on FORTRAN code to capture the nonlinearity of the vdW interactions during the buckling analysis. The results indicate that the highest critical buckling stress and the minimum lateral deflection occur for armchair and zigzag chirality, both with AB stacking mode, respectively. Moreover, the critical buckling stress is found to be directly dependent on the mode shape number regardless of in-phase or anti-phase deflection direction of layers. Lateral deflection exhibits a similar trend with mode shape in anti-phase mode; however, it is decreasing by increasing mode shape number in in-phase mode.

앏은 패널 형태의 구조물은 그 형상의 특성상 좌굴이 발생하기 쉽다. 등방성 재료에 대한 좌굴의 해석은 그동안 많은 연구가 이루어졌다. 그러나 복합재의 경우는 좌굴 현상의 거동이 매우 복잡하고 난해하기 때문에 많은 연구가 이루어지지 않았다. 적층복합재의 좌굴거동을 수치적으로 해석하기 위하여 3D 쉘요소를 적용하여 해석을 수행하였다. 본 연구에서는 3가지 종류의 layup에 대하여 비선형 좌굴 현상을 계산하였고 좌굴거동의 하중-변위 특성 관계를 규명하였다. 적층복합재의 경우 좌굴 거동이 극심한 비선형 현상을 나타내며, 또한 수치적으로 수렴하기 어렵다. 3가지 layup 적층복합재의 좌굴 거동을 해석하기 위하여 arc-length 방법을 사용하였다. 비선형 좌굴 거동의 힘-변위 곡선을 계산 하였고 또한 Tsai-Wu 파괴이론에 의하여 좌굴거동이 발생하면서 복합재의 파괴를 계산하였다.

Using closed-section ribs as longitudinal stiffeners have been proven to be an effective system for axially compressed members, however, studies on the application of these on laminated composite shell are insufficient. Thus, this study aims to evaluate the buckling behavior of the laminated composite shell when closed-section ribs were applied as longitudinal stiffeners. The effect of the rotational stiffness of the closed-section ribs on the buckling modes and strengths will be determined in this paper. The three-dimensional finite element modeling were set up using ABAQUS and a series of eigenvalue analysis were conducted, applying eight layers of the layup [(0°)4]s, [(45°/-45°)2]s and [(0°/90°)2]s on the orthotropic plates. Through the parametric studies, the increasing effect on the elastic buckling strengths due to the rotational stiffness are numerically verified, and the buckling strength of a longitudinally stiffened shell with a laminated composite material were compared with that of the isotropic material.

본 연구에서는 1차 전단변형이론을 고려한 비국소 자기-전기-탄성 나노 판의 2방향 좌굴해석에 관하여 연구하였다. 면내 전기-자기-탄성 나노 판에서 전기장과 자기장은 무시할 수 있다. 자기-전기 경계조건과 맥스웰 방정식에 따라 전기-자기-탄성 나노 판의 두께 방향에 따른 자위 및 전위의 변화가 결정된다. 자기-전기-탄성 나노 판의 탄성이론을 재 공식화하기 위하여 에링겐의 비국소 미분 구성 관계식을 사용하였다. 변분이론을 이용하여 비국소 탄성이론의 지배방정식을 연구하였 다. 비국소 이론과 국소 이론의 관계를 계산 결과를 통하여 분석하였다. 또한, 비국소 매개변수, 면내 하중 방향 그리고 형상 비에 따른 구조적 응답을 연구하였다. 계산 결과들은 전위 및 자위의 효과를 나타내었다. 이러한 계산 결과들은 자기-전기-탄성 재료로 구성된 신소재 구조물의 설계 및 해석에 사용될 수 있고 향후 연구의 비교자료가 될 수 있을 것으로 판단된다.

All structures can not be perfect due to geometric or material initial imperfections. Initial imperfections are an important factor in determining the buckling mode and are known to be important factors in evaluating the actual buckling strength. The DNV-RP-C202 design standard limits the longitudinal stiffener spacing. However, the criteria for the stiffener spacing presented in DNV-RP-C202 is a guideline derived from the curved panel theory of perfect cross-sectional shape without initial imperfections. In this study, considering geometric initial imperfections, the transition point of stiffener spacing where longitudinal stiffeners affect the buckling strength of reinforced steel wind turbine tower is analyzed using finite element analysis program. The results of finite element analysis compared with theoretical results based on the perfect shape. As a result, a more reasonable stiffener spacing considering the initial imperfections was suggested.

A pultruded fiber reinforced polymer plastic (PFRP) structural member consisted of plate elements, which is commonly used as construction member, may be considered as an orthotropic material due to its unique manufacturing process. It has different mechanical properties with respect to the longitudinal and transverse directions. This orthotropic nature of PFRP material needs to be considered in the analysis of buckling behavior. In this paper, a simplified buckling analysis for PFRP plate using geometric mean of the longitudinal and transverse mechanical properties is performed. The comparison between exact buckling analysis and simplified buckling analysis is conducted. Each analysis is performed by the Levy method and the finite element method (FEM), respectively.

This study is about the basic design technology to radically increase the structural stability of structural shell or tube, which are utilized in a variety of large structures like aircrafts, plant, bridges and buildings. Recent studies have revealed that the plates stiffened by closed-sections ribs can be designed to have greater strength as well as the reduction of used number of stiffeners. Then, the analytical models were selected based on the huge steel tube design and the finite element modeling has been conducted using the ABAQUS. Through this study, the elastic buckling strengths are compared with the flat plate buckling stress and the improved effect in the local buckling strength due to the closed-section ribs are numerically verified.

The initial production scale of wind tower is very few. But recently, the production scale of wind tower structure has increased gradually because it maximizes the efficiency in green energy. Many researchers are studying the wind tower, but there is no study about the difference of allowable buckling stress of the wind tower with and without opening. Guideline of codes and standards are very limited when designing a wind tower with an opening. It is also rarely that a study considers the design of the wind tower to be a tubular shell with or without an opening. ABAQUS, a general purpose finite element program, which provides safety evaluation and economical standards for the design and behavior of the wind tower considering the effect of opening was used in the study. Finally, results from this study can serve as reference for structural engineers, manufacturers and further studies of wind turbine when designing a tubular shell wind tower with an opening.

When an engine connecting rod is designed, it’s important to consider the buckling strength as well as deformation and durability of the rod. The buckling strength of a rod is mainly affected by the shape and area of shank cross-section and boundary conditions of its small and big ends. Buckling analysis by finite element method was carried out to evaluate the elastic buckling strength of a connecting rod that has non-uniform cross section areas. And the Merchant-Rankine formula was applied to predict the inelastic critical buckling load by considering the plastic buckling strength. Finally, the maximum allowable compressive load, which has 56.57kN, was predicted by considering the 1.7 buckling safety factor. It represents an approximately 40% greater than the maximum firing pressure.

This study numerically investigates buckling behavior of press braked steel plates with a free edge. In order to improve structural stability during construction, the top flanges of press-braked U section girder are laterally braced by the installation of prefabricated half-deck. Thus, an unbraced length is taken as the longitudinal spacing of pockets on the half-deck, which are to make composite section. This study performed 3D finite element analyses to evaluate an equivalent effective width of cold-formed flange with a free edge. Through the parametric numerical analyses, the elastic buckling stresses of the cold-formed flanges with rounded corner in the cross-section were compared with those of general flat plates. Then, the equivalent effective width of the cold-formed (press-braked) flanges were numerically examined for some representative cases.

In this paper we present the result of investigations pertaining to the buckling strength of Zelkova Serrata (Elm-like) tree column with entasis at the Muryangsujeon in Buseoksa-Temple, Korea. Wooden columns with entasis had been used in the construction of ancient architectural buildings in Korea. It was not known why did they design columns with entasis of the buildings. It is just presumed that the reason may be the compensation of optical illusion, aesthetics, and/or structural safety. The question is not answered even today and it may not be possible to answer clearly and easily. In the paper, the buckling analyses are conducted on both of the wooden column with entasis and the prismatic wooden column by the successive approximations technique and the finite element methods, respectively. The results of analyses are compared and discussed.

A study on the vibration and buckling analyses of laminated composite plates is described in this paper. In order to carry out the analyses of laminated composite plates, a NURBS-based isogeometric general plate element based on Reissner-Mindlin (RM) theory is developed. The non-uniform rational B-spline (NURBS) is used to represent the geometry of plate and the unknown displacement field and therefore, all terms required in this element formulation are consistently derived by using NURBS basis function. Numerical examples are conducted to investigate the accuracy and reliability of the present plate element. From numerical results, the present plate element can produce the isogeometric solutions with sufficient accuracy. Finally, the present isogeometric solutions are provided as future reference solutions.