• 한국강구조학회 논문집
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• 제9권4호통권33호
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• pp.557-578
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• 1997

이 연구의 목적은 매우 큰 지진하에 휨 모멘트에 의해서만 항복하는 부재와 휨 모멘트와 축 방향력에 의하여 항복하는 부재를 모델 할 수 있는 보-기둥 요소를 개발하는데 있다. 이 요소는 직렬 힌지 모델 (one-component series hinge model)로 간주 될 수 있으며, 축 방향 강성도 변화와 축 방향 소성 변형을 고려 할 수 있고 또한 단조, 주기, 임의 하중 등을 적절히 모델 할 수 있는 경화 법칙 (hardening rules)을 고려한다. 일반적으로 이 요소는 실험 결과 및 화이버 모델 (fiber model)에 비교하여 볼 때 기존의 이직선 힌지 모델 (bilinear hinge model)보다 우수한 거동을 보였고 모멘트 저항 뼈대 구조물의 강 부재의 보-기둥 거동을 적절하게 모델 할 수 있었다. 개발된 보-기둥 요소는 지진 하중하에서 구조물의 전체적인 거동과 설계에 필요한 국부 변형량을 기존의 이직선 힌지 모델 보다 매우 정확하게 예측 할 수 있다.

• Steel and Composite Structures
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• 제20권3호
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• pp.487-500
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• 2016

In order to investigate the flexural bearing capacity of panel zone of diaphragm-through joint between concrete filled square steel tubular column and steel beam, four specimens were tested under static tension loads to study the mechanical properties and bearing capacity of diaphragm-through joints with a failure mode of panel zone. Finite element models of these specimens were developed to simulate the test and compare the predicted failure modes, load-displacement curves and bearing capacities with the experimentally observed. It was found that the tensile load from the steel beam flange is mainly shared by the square steel tube and the diaphragm. The diaphragm plastic zone appears along the cross-section lines enclosed by the square steel tube and the influence of steel beam web on the plastic zone of the steel tube is significant and cannot be neglected. Computational models of yield lines on square steel tube and diaphragm are established based on the distribution pattern of the plastic zone, and an analytical method for the evaluation of the bearing capacity of the joint is proposed. The theoretical results and the experimental data are compared and found in good agreement.

• Structural Engineering and Mechanics
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• 제89권1호
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• pp.23-31
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• 2024

Ratcheting is the cyclic buildup of inelastic strain on a structure resulting from a combination of primary and secondary cyclic stress. It can lead to excessive plastic deformation, incremental collapse, or fatigue. Ratcheting has been numerically investigated on a cantilever beam, considering the current study's primary and secondary bending loads. In addition, the effect of input frequency on the onset of ratcheting has been investigated. The non-linear dynamic elastic-plastic approach has been utilized. Analogous to Yamashita's bending-bending ratchet diagram, a non-dimensional ratchet diagram with a frequency effect is proposed. The result presents that the secondary stress values fall sequentially with the increase of primary stress values. Moreover, a displacement amplification factor graph is also established to explain the effect of frequency on ratchet occurrence conditions. In terms of frequency effect, it has been observed that the lower frequency (0.25 times the natural frequency) was more detrimental for ratchet occurrence conditions than the higher frequency (2 times the natural frequency) due to the effect of dynamic displacement. Finally, the effect of material modeling of ratcheting behavior on a beam is shown using different hardening coefficients of kinematic hardening material modeling.

• Structural Engineering and Mechanics
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• 제15권5호
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• pp.513-534
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• 2003

Using fluid dampers to connect adjacent buildings for enhancing their seismic resistant performance has been recently investigated but limited to linear elastic adjacent buildings only. This paper presents a study of inelastic seismic response of adjacent buildings linked by fluid dampers. A nonlinear finite element planar model using plastic beam element is first constructed to simulate two steel frames connected by fluid dampers. Computed linear elastic seismic responses of the two steel frames with and without fluid dampers under moderate seismic events are then compared with the experimental results obtained from shaking table tests. Finally, elastic-plastic seismic responses of the two steel frames with and without fluid dampers are extensively computed, and the fluid damper performance on controlling inelastic seismic response of the two steel frames is assessed. The effects of the fundamental frequency ratio and structural damping ratio of the two steel frames on the damper performance are also examined. The results show that not only in linear elastic stage but also in inelastic stage, the seismic resistant performance of the two steel frames of different fundamental frequencies can be significantly enhanced if they are properly linked by fluid dampers of appropriate parameters.

• 한국전산구조공학회논문집
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• 제22권3호
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• pp.199-209
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• 2009

본 논문은 단조하중을 받는 초고강도 섬유보강 콘크리트 I형보의 파괴거동에 대한 3차원 유한요소해석을 수행하였다. 보통 또는 고강도 콘크리트의 구성방정식과 달리 초고강도 섬유보강 콘크리트의 재료적 특성을 나타내기 위해 인장변형률 경화관계를 고려한 탄소성 파괴역학 모델을 제안하였다. 인장영역에서는 인장경화 변형률을 고려한 다차원적 균열기준을 정의하였고, 압축영역에서는 associated flow rule을 고려한 Drucker-Prager기준을 채택하여 해석을 수행하였다. UHPFRCI형보의 지간, 프리스트레스 하중 및 단면의 영향에 관한 수치해석 결과를 실험 거동와 비교한 결과 정확한 해석 결과를 보여주었다.

• 대한조선학회지
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• 제24권3호
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• pp.43-51
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• 1987

In this paper, dynamic elastic, plastic response of beam-columns is analysed using discrete models. composed of rigid bars and springs. The equation of motion is formulated including the shear deformation effect, and the stress change of yielding points is calculated with various yielding criteria. The effect of initial axial force is considered by two ways: (1) including the effect in interaction curve only. (2) including the effect directly in the equation of motion in terms of initial stiffness method is also used in nonlinear interaction procedure. It is found that this model is very effective in analysing not only the plastic response but the elastic response, and present method is more efficient than Finite Element Method from the viewpoint of calculation time and accuracy.

• Coupled systems mechanics
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• 제8권6호
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• pp.537-553
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• 2019

In this paper we present geometrically exact Kirchhoff's initially curved planar beam model. The theoretical formulation of the proposed model is based upon Reissner's geometrically exact beam formulation presented in classical works as a starting point, but with imposed Kirchhoff's constraint in the rotated strain measure. Such constraint imposes that shear deformation becomes negligible, and as a result, curvature depends on the second derivative of displacements. The constitutive law is plasticity with linear hardening, defined separately for axial and bending response. We construct discrete approximation by using Hermite's polynomials, for both position vector and displacements, and present the finite element arrays and details of numerical implementation. Several numerical examples are presented in order to illustrate an excellent performance of the proposed beam model.

• Steel and Composite Structures
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• 제15권3호
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• pp.299-322
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• 2013

In the case of seismic-resistant composite dual moment resisting and eccentrically braced frames, the current design practice is to avoid the disposition of shear connectors in the expected plastic zones, and consequently to consider a symmetric moment or shear plastic hinges, which occur only in the steel beam or link. Even without connectors, the real behaviour of the hinge may be different from the symmetric assumption, since the reinforced concrete slab is connected to the steel element close to the hinge locations, and also due to contact friction between the concrete slab and the steel element. The paper presents the results and conclusions of experimental tests on composite portal eccentrically braced frames and beam-to-column moment-resisting joints, carried out within the CEMSIG Research Centre of the Politehnica University of Timisoara, in order to check the validity of the assumption stated above. Reference steel and composite specimens with and without connectors in the plastic zones have been tested under monotonic and cyclic seismic type loading.

• 한국구조물진단유지관리공학회 논문집
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• 제15권3호
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• pp.186-194
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• 2011

철근콘크리트 보-기둥 접합부는 철근의 복합적인 배근으로 인하여 시공성이 저하되고 철근의 정착공간이 협소하여 정착파괴가 발생할 가능성이 높다. 또한 지진하중 하에서 기둥 또는 접합부의 파괴는 구조물 전체의 파괴를 야기할 수 있기 때문에 기둥 표면에서 일정한 거리이상 떨어진 보에 소성힌지를 발생시켜 보의 파괴가 선행된 후에 기둥 및 접합부가 파괴되는 강기둥-약보의 설계 개념을 적용하여 구조물의 안전성을 확보하고 있다. 본 연구에서는 이러한 접합부의 강도 증가 및 시공성 향상을 도모하고 소성힌지를 보의 내측방향으로 이동시키기 위한 방안으로 보 주인장 철근과 접합부 보강 철근으로 헤디드 바를 활용하고자 하였다. 이를 위해 헤디드 바로 보강된 철근콘크리트 보-기둥 접합부에 대해 3차원 유한요소 해석을 수행하였다. 해석결과의 정확성을 검증하기 위하여 선행연구자에 의해 실험된 부재와 동일한 변수에 대한 해석을 수행하여 그 결과를 비교하였으며, 헤디드바의 우수성을 확인하기 위한 변수를 추가하여 해석을 수행하였다. 해석결과 보 주인장 철근의 정착방법으로 헤디드 바를 사용함으로써 유사한 구조성능 하에서 시공성 향상을 도모할 수 있음을 확인하였다. 또한 헤디드 바를 접합부에 보강함으로써 설계자가 의도한 위치에 소성힌지를 발생시킬 수 있었으며, 주기하중 하에서 에너지 소산능력의 증가, 강성 감소의 최소화 및 극한응력을 향상시키는 결과를 얻었다.

• Steel and Composite Structures
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• 제33권1호
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• pp.143-162
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• 2019

A number of desirable characteristics concerning excellent durability, aesthetics, recyclability, high ductility and fire resistance have made stainless steel a preferred option in engineering practice. However, the relatively high initial cost has greatly restricted the application of stainless steel as a major structural material in general construction. This drawback can be partially overcome by introducing composite stainless steel-concrete structures, which provides a cost-efficient and sustainable solution for future stainless steel construction. This paper presents a preliminary numerical study on stainless steel-concrete composite beam-to-column joints with bolted flush endplates. In order to ensure a consistent corrosion resistance within the whole structural system, all structural steel components were designed with austenitic stainless steel, including beams, columns, endplates, bolts, reinforcing bars and shear connectors. A finite element model was developed using ABAQUS software for composite beam-to-column joints under monotonic and symmetric hogging moments, while validation was performed based on independent test results. A parametric study was subsequently conducted to investigate the effects of several critical factors on the behaviour of composite stainless steel joints. Finally, comparisons were made between the numerical results and the predictions by current design codes regarding the plastic moment capacity and the rotational stiffness of the joints. It was concluded that the present codes of practice generally overestimate the rotational stiffness and underestimate the plastic moment resistance of stainless steel-concrete composite joints.