• 한국전산구조공학회논문집
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• 제34권6호
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• pp.393-401
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• 2021

본 논문에서는 폭발하중을 받는 부재의 저항성능 평가를 위한 모멘트-곡률 관계 기반 수치해석 기법을 소개한다. 직접전단 파괴 모드를 고려하기 위하여 경험적인 직접전단응력-슬립양 관계를 기반으로 하는 무차원 스프링 요소를 도입하였다. 재료에 대해 정의된 동적증가계수 식을 바탕으로 단면의 모멘트-곡률 관계에 직접적으로 적용가능한 단면의 곡률 변화율에 따른 동적증가계수 식을 제작하였다. 또한 부착슬립의 영향을 고려하기 위하여 소성힌지영역 내에 등가 휨강성을 도입하였다. 제안된 수치해석 모델의 타당성 검증을 위하여 실험결과와의 비교연구를 수행하였으며, 단자유도계 모델의 해석결과와의 비교를 통해 본 수치해석 모델의 우수성을 확인하였다. P-I 선도를 제작하여 부재의 휨 파괴 및 직접전단 파괴에 대한 저항성능을 평가하였으며, 매개변수 연구를 수행하여 P-I 선도 및 저항성능의 변화를 확인하였다.

• 한국강구조학회 논문집
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• 제21권2호
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• pp.155-164
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• 2009

본 논문에서는 용접철골모멘트골조의 비선형 동적 연쇄붕괴 해석을 위해 인장-휨 거동을 반영한 효율적인 병렬 소성힌지를 제안하였다. 본 목적을 위해 재료적/기하학적 비선형 유한요소해석을 이용한 변수연구를 통해 기둥이 손실된 2경간 보의 항복후 휨거동과 모멘트-축인장력 상호작용을 살펴보았다. 유한요소해석결과를 토대로 보의 모멘트-축인장력 상호작용 관계를 일련의 선형으로 근사화한 소성힌지모델을 제안하고, 이를 OpenSees 프로그램에 적용하여 용접철골모멘트골조의 비선형 동적 연쇄붕괴해석을 수행하였다. 비선형 동적 유한요소해석을 통하여 본 연구에서 제안한 힌지모델의 효율성과 정확도를 검증하였다. 또한 본 연구 결과는 연쇄붕괴 해석 및 설계에 적절한 현수작용효과의 포함여부가 중요함을 보여준다.

• Nuclear Engineering and Technology
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• 제49권1호
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• pp.254-266
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• 2017

Finite-element analysis based on elastic-perfectly plastic material was conducted to examine the influence of structural deformations on collapse loads of circumferential through-wall critically cracked $90^{\circ}$ pipe bends undergoing in-plane closing bending and internal pressure. The critical crack is defined for a through-wall circumferential crack at the extrados with a subtended angle below which there is no weakening effect on collapse moment of elbows subjected to in-plane closing bending. Elliptical and semioval cross sections were postulated at the bend regions and compared. Twice-elastic-slope method was utilized to obtain the collapse loads. Structural deformations, namely, ovality and thinning, were each varied from 0% to 20% in steps of 5% and the normalized internal pressure was varied from 0.2 to 0.6. Results indicate that elliptic cross sections were suitable for pipe ratios 5 and 10, whereas for pipe ratio 20, semioval cross sections gave satisfactory solutions. The effect of ovality on collapse loads is significant, although it cancelled out at a certain value of applied internal pressure. Thinning had a negligible effect on collapse loads of bends with crack geometries considered.

• Steel and Composite Structures
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• 제13권2호
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• pp.171-185
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• 2012

The calculation of fire resistance for a composite structural element comprises the calculation of the temperature within its cross-section and of the load bearing capacity, considering the evolution of the steel and concrete mechanical properties, function of the temperature. The paper proposes a method to calculate the bending capacity under ISO fire, for Slim Floor systems using asymmetric steel beams, with a wider lower flange or a narrow upper flange welded onto a half hot-rolled profile. The temperatures in the cross-section are evaluated by means of empirical formulas determined through a parametrical analysis, performed with the special purpose non-linear finite element program SAFIR. Considering these formulas, the bending capacity may be calculated, using an analytical approach to determine the plastic bending moment, for different fire resistance demands. The results obtained with this simplified method are validated through numerical analysis.

• Steel and Composite Structures
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• 제11권1호
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• pp.1-19
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• 2011

The introduction of the Eurocodes makes plastic design criteria available also for composite bridges, leading to more economical solutions compared with previous elastic design rules. Particularly for refurbishment old bridges with higher actual traffic loads, up to date outside the scope of the Eurocodes, strengthening should therefore be avoidable or at least be necessary only to a minor extent. For bridges with smaller spans and compact cross sections, the plastic load bearing capacity is clearly justified. In this work, however, the focus is placed on long span continuous composite bridges with deep, longitudinally stiffened girders, susceptible to local buckling. In a first step, the elastic - plastic cross section capacity of the main girder in bending is studied as an isolated case, based on high preloads acting on the steel girder only, due to the common assembling procedure without scaffolding. In a second step, the effects on the whole structure are studied, because utilising the plastic section capacity at midspan leads to a redistribution of internal forces to the supports. Based on the comprehensive study of an old, actual strengthened composite bridge, some limitations for plastic design are identified. Moreover, fully plastic design will sometimes need additional global analysis. Practical recommendations are given for design purposes.

• 한국강구조학회 논문집
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• 제15권3호
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• pp.261-269
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• 2003

편심브레이스골조의 설계에서 가장 중요한 인자는 링크보의 길이이다. 링크보의 길이에 따라 편심브레이스골조의 거동과 파괴메카니즘이 결정된다. 링크보의 길이가 짧아져 전단력에 의해 소성화되면 중심브레이스골조와 대등한 수평방향강성과 모멘트 연성골조의 연성을 동시에 확보할 수 있다. 또한 링크보의 길이가 길어지게 되면 링크보는 모멘트에 의해 소성화 되어 연성적인 거동을 확보할 수 없게 된다. 근래에 이르러 건축계획적인 측면에서는 링크보의 길이가 길어지는 것이 입면 및 단면계획이 용이하며, 그 필요성이 증대되고 있지만, 모멘트 링크에 대한 기존의 연구가 많이 수행되어 있지 않으며, 이와 관련된 자료가 부족한 실정이다. 본 연구에서는 실험을 통해 다양한 접합디테일을 가진 모멘트링크보의 거동을 규명하고 모멘트링크보의 거동을 개선시킬 수 있는 접합디테일을 제시하고자 한다. 4개의 접합 디테일을 가진 총 16개의 실험체를 계획하여 이력거동 실험을 수행하였다.

• 소성∙가공
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• 제16권7호
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• pp.509-515
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• 2007

As the springback of sheet metal during unloading may cause deviation from a desired shape, accurate prediction of springback is essential for the design of sheet stamping operations. When considering the case of a sheet metal being bent to radius $\rho$ that is such that the maximum stress induced exceed the elastic limit of the material, plastic strain in the outer surface will occur and the material will take a permanent set: but since, on removing the bending moment, the recovery of the material is not uniform across the thickness, springback will occur and the radius $\rho$ will not be maintained. Furthermore, when a tensile load being applied to each end of specimen, the tensile stress due to bending is increased and the compressive stress is decreased or cancelled and eventually the whole specimen may be in varying degree of tension. On the removal of the applied load the specimen loses its elastic strain by contracting around the contour of the block, the radius $\rho$ will be determined by the residual differential strain. Therefore in this study the springback is analytically estimated by the residual differential strains between upper and lower surfaces of greatest radius after elastic recovery, and a springback model based on the bending moment is also analytically derived for comparison purpose.

• Structural Engineering and Mechanics
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• 제15권2호
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• pp.199-223
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• 2003

The formulation of a non-linear shear deformable shell element is presented for the solution of stability problems of stiffened plates and shells. The formulation of the geometrical stiffness presented here is exactly defined on the midsurface and is efficient for analyzing stability problems of thick plates and shells by incorporating bending moment and transverse shear resultant force. As a result of the explicit integration of the tangent stiffness matrix, this formulation is computationally very efficient in incremental nonlinear analysis. The element is free of both membrane and shear locking behaviour by using the assumed strain method such that the element performs very well in the thin shells. By using six degrees of freedom per node, the present element can model stiffened plate and shell structures. The formulation includes large displacement effects and elasto-plastic material behaviour. The material is assumed to be isotropic and elasto-plastic obeying Von Mises's yield condition and its associated flow rules. The results showed good agreement with references and computational efficiency.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1990년도 PROCEEDINGS OF THE FIRST KOREA-JAPAN JOINT GEOTECHNICAL SEMINAR ON EXCAVATION and TUNNELING IN URBAN AREAS
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• pp.111-128
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• 1990

Three numerical analysis carried out for the design of a diaphragm wall were examined by the results of field observation data. Utilizing the wall stiffness, supporting system and construction sequence, the relative merits of those factors on the analysis of diaphragm wall have been investigated and their effects are compared tilth the observed behaviour of the wall. The predicted bending moment and wall displacement by elasto-plastic method agreed well with the observed values. The rigid slab supported system (i.e Top-Down Method) found to be the most effective way of controlling ground movement.

• 대한기계학회논문집A
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• 제20권4호
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• pp.1263-1274
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• 1996

In this paper, as elastic-plastic fracture toughness test under mixed mode loading was proposed using a single edge-cracked specimen subjected to bending moment(M), shearing force(F), and twisting moment(T). The J-integral of a crack in the specimen is expressed in the form J=$J_I$+ $J_II$$J_III$, where $J_I$, $J_II$ and $J_III$ are the components of mode I, mode II and mode III deformation, respectively. $J_I$, $J_II$ and $J_III$ can be estimated from M-$\theta$ ($\theta$;crack opening angle), F-U(U; crack shear displacement) and T-$\alpha$ ($\alpha$;crack twisting angle). In order to obtain the the M<-TEX>$\theta$, F-U and T-$\alpha$ diagram inreal time, a new deformaiton gage for mixed mode loading was proposed using the optical position sensing device(PSD). The elastic-plastic fracture toughness test was carried out with an aluminum alloy. The loading apparatus was designed and manufactured for this experiment. For the loading condition of the crack initatio in the mixed mode, the MMT -3(mode I+ mode II+ mode III) has the lowest values out of the all specimens. This implies that MMT-3 is possible of the crackinitation at lower load, if the specimen acts on together with the torque under the same loading condition. An elastic-plastic fracture toughness test using the PSD brings a successful experimentation in measuring the crack deformation(mode I+ mode II+ mode III).