• Smart Structures and Systems
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• 제22권3호
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• pp.315-326
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• 2018

This paper presents a novel time-domain method for the identification of plastic rotations and stiffness parameters of single-bay frames with nonlinear plastic hinges. Each plastic hinge is modelled as a pseudo-semi-rigid connection with nonlinear hysteretic moment-curvature characteristics at an element end. Through the comparison of the identified end rotations of members that are connected together, the plastic rotation that furnishes information of the locations and plasticity degrees of plastic hinges can be identified. The force consideration of the frame members may be used to relate the stiffness parameters to the elastic rotations and the excitation. The damped-least-squares method and damped-and-weighted-least-squares method are adopted to estimate the stiffness parameters of frames. A noise-removal strategy employing a de-noising technique based on wavelet packets with a smoothing process is used to filter out the noise for the parameter estimation. The numerical examples show that the proposed method can identify the plastic rotations and the stiffness parameters using measurements with reasonable level of noise. The unknown excitation can also be estimated with acceptable accuracy. The advantages and disadvantages of both parameter estimation methods are discussed.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2002년도 추계학술발표대회 논문집
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• pp.123-126
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• 2002

To evaluate the bending collapse behavior of an aluminum square tube, a finite element simulation for the four-point bending test was suggested. Local buckling deformation near the center of an aluminum tube specimen was induced which has been partly inserted by two steel bars. Simulation results showed good agreements with those of experiment.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 가을 학술발표회 논문집(II)
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• pp.867-872
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• 2000

A 1:12 scale 10-story RC building structure was constructed and the experiment was performed. The test results are presented and compared with the results of the analysis conducted with DRAIN-2DX. It is concluded that some local deformations cannot be described reasonably with the wall model using only Plastic Hinge Beam-Column Element(TYPE02) in DRAIN-2DX whereas the strength and stiffness of the whole structure can be predicted with high reliability.

• Computers and Concrete
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• 제13권2호
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• pp.221-234
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• 2014

A nonlinear finite element analysis using ANSYS is used to evaluate the seismic behavior of reinforced concrete exterior beam-column joints. The behavior of the finite element models under cyclic loading is compared with the experimental results. Two beam-column joint specimens (SH and SHD) with square hoop confinement in joint and throughout the column with detailing as per IS 13920 are studied. The specimen SHD was provided with additional diagonal bars from column to beam to relocate the plastic hinge formation from beam-column interface. The load-displacement relationship, joint shear stress and strain in beam obtained from numerical study showed good agreement with the experimental results. This investigation proves that seismic behaviour of reinforced concrete beam-column joints under reversed cyclic loading can be evaluated successfully using finite element modeling and analysis.

• Steel and Composite Structures
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• 제31권6호
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• pp.617-628
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• 2019

As an extremely destructive accident, progressive collapse is defined as the spread of an initial local failure from element to element, resulting eventually in the collapse of an entire structure or disproportionately large of it. To prevent the occurrence of it and evaluate the ability of structure resisting progressive collapse, the nonlinear static procedure is usually adopted in the whole structure design process, which considered dynamic effect by utilizing Dynamic Increase Factor (DIF). In current researches, the determining of DIF is performed in full-rigid frame, however, the performance of beam-column connection in the majority of existing frame structures is not full-rigid. In this study, based on the component method proposed by EC3 guideline, the expression of extended endplate connection performance is further derived, and the connection performance is taken into consideration when evaluated the performance of structure resisting progressive collapse by applying the revised plastic P-M hinge. The DIF for structures with extended endplate beam-column connection have been determined and compared with the DIF permitted in current GSA guideline, the necessity of considering connection stiffness in determining the DIF have been proved.

• Computers and Concrete
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• 제32권5호
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• pp.527-541
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• 2023

This paper emphasizes the use of CFT columns in frame structures subjected to strong horizontal forces and shows that the efficiency of using CFT columns is increased when the plastic design approach is adopted. Because the plastic design approach is based on redistribution of the force of the internal member, a double node for the rotational degrees of freedom, where the adjacent two rotational degrees of freedom can be connected by a non-dimensional spring element, is designed and implemented into the formulation. In addition, an accompanying criterion is considered in order to make it possible to describe the continuous moment redistribution in members connected to a nodal point up to a complete plastic state. The efficiency of CFT columns is reviewed in comparison with RC columns in terms of the cost and the resistance capacity, as defined by a P-M interaction diagram. Three representative frame structures are considered and the obtained results show that the most efficient and economical design can be expected when the use of CFT columns is considered on the basis of the plastic design, especially when a frame structure is subjected to significant horizontal forces, as in a high-rise building.

• 한국전산구조공학회논문집
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• 제24권5호
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• pp.513-520
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• 2011

본 연구에서는 스트라치 시스템의 긴장설치과정 해석을 수행하기 위한 개선된 명시적 해석법을 제안하였다. 스트라치 시스템은 Stressed-Arch에서 유래한 용어로 슬리브에 의한 갭이 도입된 유동 하현재가 내부의 긴장재에 의한 초기장력의 도입으로 서서히 닫히게 되고, 이에 따라 전체 구조물이 상승하여 최종적인 아치형태의 구조물을 형성하는 독창적인 구조시스템이다. 스트라치 시스템의 초기장력 도입과정을 긴장설치(stress-erection process) 과정이라 하며, 초기곡률의 도입에 따라 유동 상현재에는 과도한 초기변형이 발생하여 소성거동에 의한 강체회전이 발생하는 불안정 구조물이 된다. 본 연구에서는 이러한 스트라치 시스템의 불안정 거동특성을 해석하기 위해서 소성힌지가 적용된 보-기둥요소를 사용하여 유동상현재를 모델링하였고, 불안정 구조물의 해석법에 효과적으로 사용되는 동적이완법의 개선된 알고리즘을 개선하여, 실제 스트라치 구조물의 긴장설치과정 해석을 수행하였으며, 실제 프로젝트에 대한 해석결과의 분석을 통하여 제안된 해석법의 적용성을 검증하였다.

• 한국정밀공학회지
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• 제27권5호
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• pp.75-84
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• 2010

The aim of this paper is to design the blank shape of SPFH 590 high strength steel for stamping of the center hinge of automotive via numerical analyses and experiments for multi-stages transfer forming process. Three-dimensional elasto-plastic finite element analyses for the transfer forming process with six stages were performed using a commercial code AUTOFORM V4.2. The influence of the blank shape on the formability and the shape conformity were quantitatively examined through the FE analyses. From the results of the FE analysis, a feasible shape of the blank and the forming load were estimated. Stamping experiments were carried out using the proposed blank shape. The results of experiments were shown that the center hinge parts with the desired shapes can be manufactured successfully as the proposed blank shape is used. Through the comparison of the results of the experiments with those of the analyses, it was shown that the estimation of blank shape using the FE analysis is a proper methodology to create a feasible shape of the blank for the center hinge of automotive.

• 한국강구조학회 논문집
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• 제15권3호
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• pp.299-311
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• 2003

점진적 소성화를 고려한 공간뼈대구조의 극한강도를 평가하기 위한 비선형 유한요소 해석법을 제시한다. 유한한 회전각의 2차항 까지 고려된 개선된 변위장을 도입하여 결과적으로 축력뿐만 아니라 휨모멘트 그리고 비틂모멘트에 의한 비선형 효과를 모두 고려한다. 탄-소성 해석을 위하여 소성힌지 개념을 도입하고 비선형 해석방법으로 하중 및 변위증분법을 이용한다. 잔류응력 분포에 의거한 초기항복함수를 정의하고 축력뿐만 아니라 모멘트의 함수로 표현되는 소성영역함수를 사용하여 flow rule과 normality condition을 적용하여 탄-소성 강도매트릭스를 도출한다. 계산시간이 빠른 기존의 소성힌지 해석기법을 사용하는 동시에 소성영역의 진전효과를 효율적으로 나타내었다. 요소의 소성화 진행정도를 나타내는 파라미터를 도입하고 여러 가지 강도감소모델을 사용하여 극한해석을 수행하여 그 결과를 소성영역해석, 쉘요소를 이용한 정밀해석 그리고 실험결과와 비교하였다.

• Earthquakes and Structures
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• 제22권2호
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• pp.203-218
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• 2022

In this paper, quasi-static tests were carried out on three prefabricated reinforced concrete column-steel beam (RCS) sub-assemblages with floor slabs and one comparison specimen without floor slab. The effects of axial compression and floor slab on the seismic performance were studied, and finite element simulations were conducted using ABAQUS. The results showed that the failure of prefabricated RCS sub-assemblages with floor occurred as a joint beam and column failure mode, while failure of sub-assemblages without floor occurred due to beam plastic hinge formation. Compared to the prefabricated RCS sub-assemblages without floor slab, the overall stiffness of the sub-assemblages with floor slab was between 19.2% and 45.4% higher, and the maximum load bearing capacity increased by 26.8%. However, the equivalent viscosity coefficient was essentially unchanged. When the axial compression ratio increased from 0.24 to 0.36, the hysteretic loops of the sub-assemblages with floor became fuller, and the load bearing capacity, ductility, and energy dissipation capacity increased by 12.1%, 12.9% and 8.9%, respectively. Also, the initial stiffness increased by 10.2%, but the stiffness degradation accelerated. The proportion of column drift caused by beam end plastic bending and column end bending changed from 35% and 46% to 47% and 36%, respectively. Comparative finite element analyses indicated that the numerical simulation outcomes agreed well with the experimental results.