• Steel and Composite Structures
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• 제32권1호
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• pp.1-19
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• 2019

The aim of the paper is the prediction of the seismic collapse mode of steel storage pallet racks under seismic loads. The attention paid by the researchers on the behaviour of the industrial steel storage pallets racks is increased over the years thanks to their high dead-to-live load ratio. In fact, these structures, generally made by cold-formed thin-walled profiles, present very low structural costs but can support large and expensive loads. The paper presents a prediction of the seismic collapse modes of multi-storey racks. The analysis of the possible collapse modes has been made by an approach based on the kinematic theorem of plastic collapse extended to the second order effects by means of the concept of collapse mechanism equilibrium curve. In this way, the dissipative behaviour of racks is determined with a simpler method than the pushover analysis. Parametric analyses have been performed on 24 racks, differing for the geometric layout and cross-section of the components, designed in according to the EN16618 and EN15512 requirements. The obtained results have highlighted that, in all the considered cases, the global collapse mechanism, that is the safest one, never develops, leading to a dangerous situation that must be avoided to preserve the structure during a seismic event. Although the studied racks follow all the codes prescriptions, the development of a dissipative collapse mechanism is not achieved. In addition, also the variability of load distribution has been considered, reflecting the different pallet positions assumed during the in-service life of the racks, to point out its influence on the collapse mechanism. The information carried out from the paper can be very useful for designers and manufacturers because it allows to better understand the racks behaviour in seismic load condition.

• 한국구조물진단유지관리공학회 논문집
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• 제9권1호
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• pp.233-241
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• 2005

본 연구는 콘크리트로 충전한 절곡된 단면을 갖는 각형강관 기둥의 부착특성을 매입인발(Pull-out) 시험을 통해 평가하였다. 시험체는 단면 $250{\times}250mm$의 강관 단면에 콘크리트를 충진한 PSSC기둥으로 표준형(P), 사다리꼴(I), 직사각형(II), 역사다리꼴(III)의 4가지 형태(Fig. 3)와, 부착길이에 대한 폭비 (L/D=2.0, 2.5, 3.0) 단면의 폭두깨비(d/t)으로 설정하여 총 13로 하였다. 실험결과 얇은 판요소 절곡된 강관과 콘크리트의 부착거동은 일반적인 부착거동과 유사하게 화학적 부착과 기계적 부착의 형태로 거동하였으며, 부착응력은 강판의 절곡형태가 (equation omitted)순으로 높게 나타났다. 또한 (equation omitted)타입 시험체의 경우에는 얇은 판요소를 갖는 단면임에도 불구하고 AIJ에서 제시하고 있는 $0.147N/mm^2$의 값을 상회하는 것으로 나타나 부착응력을 고려할 수 있을 것으로 판단되었다.

• 한국추진공학회지
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• 제19권6호
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• pp.64-71
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• 2015

스피닝 공정은 축대칭의 얇은 두께를 가지고 있는 속이 빈 실린더형 단면을 가지고 있는 부품에 일반적으로 사용된다. 전통적인 스피닝 제작 기술은 컨벤셔널 스피닝과 파워 스피닝(전단 스피닝과 유동성형)으로 구분된다. 액체추진로켓의 연소기의 재생냉각 챔버와 확대노즐부에서 적용된 스피닝에 대한 문헌조사를 수행하였다. 연소실과 노즐의 제작에 사용되는 스피닝은 대부분 맨드럴을 사용하였다. 최근에는 전통적인 냉간 스피닝에 비해 열간 스피닝도 많이 사용되고 있었다.

• Wind and Structures
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• 제15권3호
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• pp.189-208
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• 2012

Lock-in and drag amplification phenomena are studied for a flexible cantilever using a simplified fluid-structure interaction approach. Instead of solving the 3D domain, a simplified setup is devised, in which 2D flow problems are solved on a number of planes parallel to the wind direction and transversal to the structure. On such planes, the incompressible Navier-Stokes equations are solved to estimate the fluid action at different positions of the line-like structure. The fluid flow on each plane is coupled with the structural deformation at the corresponding position, affecting the dynamic behaviour of the system. An Arbitrary Lagrangian-Eulerian (ALE) approach is used to take in account the deformation of the domain, and a fractional-step scheme is used to solve the fluid field. The stabilization of incompressibility and convection is achieved through orthogonal quasi-static subscales, an approach that is believed to provide a first step towards turbulence modelling. In order to model the structural problem, a special one-dimensional element for thin walled cross-section beam is implemented. The standard second-order Bossak method is used for the time integration of the structural problem.

• 한국소음진동공학회논문집
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• 제25권7호
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• pp.510-517
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• 2015

The free vibration and stability analysis of a spinning composite shaft modelled as a thin-walled closed beam is performed for several design parameters, such as ply angle, aspect ratio, and spin speed. The governing equations of spinning shafts based on the Timoshenko beam theory are derived via Hamilton's variational principle. Coriolis acceleration and anisotropy of constituent materials are incorporated in the derivation. The equations of motion are then transformed to the standard form of an eigenvalue problem for free vibration and stability analysis. Analytical results both for uniform circular cylindrical shaft and rectangular cross-section shaft are obtained by using extended Galerkin method, and the results are compared with those from FEM ANSYS analysis for a verification.

• Advances in aircraft and spacecraft science
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• 제3권1호
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• pp.1-14
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• 2016

The Carrera Unified Formulation (CUF) is here extended to perform free-vibrational analyses of rotating structures. CUF is a hierarchical formulation, which enables one to obtain refined structural theories by writing the unknown displacement variables using generic functions of the cross-section coordinates (x, z). In this work, Taylor-like expansions are used. The increase of the theory order leads to three-dimensional solutions while, the classical beam models can be obtained as particular cases of the linear theory. The Finite Element technique is used to solve the weak form of the three-dimensional differential equations of motion in terms of "fundamental nuclei", whose forms do not depend on the adopted approximation. Including both gyroscopic and stiffening contributions, structures rotating about either transversal or longitudinal axis can be considered. In particular, the dynamic characteristics of thin-walled cylinders and composite blades are investigated to predict the frequency variations with the rotational speed. The results reveal that the present one-dimensional approach combines a significant accuracy with a very low computational cost compared with 2D and 3D solutions. The advantages are especially evident when deformable and composite structures are analyzed.

• Structural Engineering and Mechanics
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• 제87권6호
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• pp.541-554
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• 2023

An unbraced cantilever beam subjected to loads which cause bending about the major axis may buckle in a flexuraltorsional mode by deflecting laterally and twisting. For the efficient design of these structures, design engineers require a simple accurate equation for the elastic flexural-torsional buckling load. Existing solutions for the flexural-torsional buckling of cantilever beams have mainly been derived by numerical methods which are tedious to implement. In this research, an attempt is made to derive a theoretical equation by the energy method using different buckled shapes. However, the results of a finite element flexural-torsional buckling analysis reveal that the buckled shapes for the lateral deflection and twist rotation are different for cantilever beams. In particular, the buckled shape for the twist rotation also varies with the section size. In light of these findings, the finite element flexural-torsional buckling analysis was then used to derive simple accurate equations for the elastic buckling load and moment for cantilever beams subjected to end point load, uniformly distributed load and end moment. The results are compared with previous research and it was found that the equations derived in this study are accurate and simple to use.

• Steel and Composite Structures
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• 제53권1호
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• pp.61-75
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• 2024

Thin-walled concrete-filled U-shaped steel beams have been recently used in building structures for shortening the construction period and cost efficiency of structural members. In this study, the flexural and shear behavior of newly developed bolt-connected U-shaped steel beams filled with concrete was experimentally evaluated considering load conditions for positive and negative moments, and types of U-shaped steel sections. Because the cross sections are not symmetrical about a horizontal axis, compressive buckling of bottom plates was observed along with web shear buckling under negative moment loading, while the slab concrete under compression was crushed under a positive moment loading. Despite such different shear failure modes depending on load conditions, the shear strength of the composite beams can be conservatively predicted using AISC 360-16 and Eurocode 4. Although the shear contribution of filled concrete is neglected according to the current design codes, the shear capacity of the steel web considering the shear buckling coefficient corresponding to the web width-to-thickness ratio reasonably predicts the test results. In addition, for deep composite beams, the longitudinal lips of a U-shaped steel section anchored into filled concrete can improve the interfacial bond between steel and concrete, thereby enhancing the shear contribution of the steel web.

• 대한토목학회논문집
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• 제11권4호
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• pp.45-54
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• 1991

선형변단면관형(線形變斷面管型) 단면(斷面) 부재(部材)의 3차원(次元) 공간(空間)에서의 고유진동해석(固有振動解析)을 위하여 회전관성(回轉慣性)도 포함하는 질량(質量) 행열(行列)을 유도하였다. 유도과정에서 정확한 변위함수(變位函數)를 사용했다. 일반적으로 많이 사용되는 변단면(變斷面) 부재(部材)의 경사(傾斜)는 매우 작으므로 '정형적분형(整形積分型)'으로 표현된 행열(行列)을 사용하여 변단면(變斷面) 부재(部材)를 포함하는 구조물을 해석할 때에 신빙성(信憑性)없는 결과를 얻게 된다. 이러한 수치적(數値的) 오류(誤謬)를 피하기 위하여 '급수형(級數型)'의 전개식(展開式)을 유도했다. 변단면(變斷面) 부재(部材)의 구조물(構造物)을 해석하기 위하여 본(本) 연구(硏究)에서 유도(誘導)된 질량(質量) 행열(行列)을 사용하여 구한 고유진동수(固有振動數)와 분할 부재(部材)를 균일단면(均一斷面) 탑형태(塔形態)로 표현하여 구한 고유진동수(固有振動數)를 비교(比較)하여 본 연구결과 효율성(效率性)과 정확성(正確性)이 증진(增進)된 것을 확인하였다.

• 대한토목학회논문집
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• 제14권5호
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• pp.1023-1031
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• 1994

선형변단면(線形變斷面) I-형(型) 부재(部材)의 3차원(次元) 공간(空間)에서의 고유진동해석(固有振動解析)을 위하여 회전관성(回轉慣性)도 포함하는 컨시스턴트 질량행렬(質量行列)을 유도하였다. 유도과정(誘導過程)에서 정확한 형상함수(形狀函數)를 사용했다. 일반적으로 많이 사용되는 변단면부재(變斷面部材)의 경사(傾斜)는 매우 작으므로 '정형식(整形式)'으로 표현된 행렬(行列)을 사용하여 변단면(變斷面) 부재(部材)를 포함하는 구조물(構造物)을 해석할 때에 신빙성 없는 결과를 얻게 된다. 이러한 수치적(數値的) 오류(誤謬)를 피하기 위하여 '급수식(級數式)'을 유도했다. 변단면(變斷面) 부재(部材)의 구조물(構造物)을 해석하기 위하여 본 연구에서 유도된 질량행렬(質量行列)을 사용하여 구한 고유진동수(固有振動數)와 변단면(變斷面) 부재(部材)를 균일단면(均一斷面)의 탑형태(塔形態)로 표현하여 ANSYS에서 구한 고유진동수(固有振動數)를 비교하여 본 연구 결과 효율성과 정확성이 증진된 것을 확인하였다. 본 연구에서 유도된 질량행렬(質量行列)은 변단면(變斷面) 부재(部材)와 균일단면(均一斷面) 부재(部材)의 자유진동해석(自由振動解析)에 사용할 수 있다.