• Wind and Structures
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• 제14권1호
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• pp.1-14
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• 2011

Open frame structures, such as those commonly found in industrial process facilities, are often densely occupied with process related equipment. This paper presents a method for estimating wind loads for high-solidity open frame structures that differs from current approaches, which accumulate wind load contributions from various individual structure components. The method considers the structure as a porous block of arbitrary plan dimension that is subject to wind from any direction. The proposed method compares favorably with wind tunnel test results for similar structures. The possibility of defining an upper bound force coefficient is also discussed.

• 대한기계학회논문집A
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• 제33권8호
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• pp.819-825
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• 2009

An open frame structure is fastened by bolt joints for strength and shock attenuation. Therefore the full finite element model of an open frame structure should be properly modeled including bolt joints for strength analysis of the frames and joint assemblies which are operated under multi-loading conditions such as driving, drop, inertia and torsional loads. Then the joints and frames must satisfy the specified allowable strength constraints. Because the full finite element model has a large number of elements to perform strength analysis, a detailed fine bolt analysis seems to be very expensive. Therefore bolts of the full finite element model are approximately modeled by coupling method to constrain degree of freedoms between adjacent nodes. However, the coupling method can exaggerate stress results at the constrained nodes. Thus a detailed bolt analysis and a theoretical/experiential formula of bolts for a worst bolt joint are performed using reaction force applied both bolt and bolt joint. Finally, the results from the two methods are compared and discussed to verify the safety of the open frame structure.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2008년도 추계학술대회A
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• pp.523-528
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• 2008

An open frame structure is fastened by bolt joints for strength and shock attenuation. Therefore the full finite element model of an open frame structure should be properly modeled including bolt joints for strength analysis of the frames and joint assemblies which are operated under multi-loading conditions such as driving, drop, inertia and torsional loads. Then the joints and frames must satisfy the specified allowable strength constraints. Because the full finite element model has a large number of elements to perform strength analysis, a detailed fine bolt analysis seems to be very expensive. Therefore bolts of the full finite element model are approximately modeled by constraints equations to constrain degree of freedoms between adjacent nodes. However, the constraints equation method can exaggerate stress results at the constrained nodes. Thus a detailed bolt analysis and a theoretical/experiential formula of bolts for a worst bolt joint are performed using reaction force applied both bolt and bolt joint. Finally, the results from the two methods are compared and discussed to verify the safety of the open frame structure.

• 대한토목학회논문집
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• 제32권3C호
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• pp.121-127
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• 2012

본 논문은 터널건설로 인해 발생된 인접지반에서의 지반변위가 프레임구조물에 미치는 영향을 터널 시공조건(지반손실)을 달리하면서 조사한 것이다. 터널굴착에 의해 발생된 지반변위에 노출된 4층 오픈 프레임구조물과 블록으로 채워진 프레임구조물이 서로 다른 시공조건(지반손실)에 노출될 때 발생되는 구조물 거동을 수치해석을 통해 조사하였다. 오픈 프레임구조물은 탄성구조물로서 모델링 한 반면, 블록으로 채워진 프레임구조물은 소요전단 및 인장강도 이상의 응력이 발생할 때 구조물에 실제크랙이 발생할 수 있도록 모델링하였다. 터널굴착유발 지반변위에 노출된 두 서로 다른 프레임구조물의 거동 및 손상정도를 터널 시공조건에 따라 조사하였으며, 발생된 구조물의 거동 및 손상정도는 구조물에 발생한 변형, 크랙크기 및 분포를 고려하여 서로 비교하였다. 뿐만 아니라, 다양한 시공조건(지반손실)의 변화에 의해 구조물에 유발될 수 있는 손상정도의 크기를 손상도 예측기준(Son and Cording, 2005)을 사용하여 제시하였다. 이러한 결과들은 향후 터널굴착으로 인해 유발되는 인접 프레임구조물의 손상을 제어하고 최소화하는데 필요한 정보를 제공할 것이다.

• International Journal of Advanced Culture Technology
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• 제8권2호
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• pp.159-164
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• 2020

The response analysis of frame structure with open section beams considering warping conditions and short duration load have been performed. When a beam of frame structure is subjected under torsional moment, the cross section will deform a warping as well as twist. For some thin-walled sections warping will be large, and accompanying warping restraint will induce axial and shear stresses and reduce the twist of beam which stiffens the beam in torsion. Because of impact or blast loads, the wave propagation effects become increasingly important as load duration decreases. This paper presents that a warping restraint in finite element model effects the behavior of beam deformation, dynamic mode shape and response analysis. The computer modelling of frame is discussed in linear beam element model and linear thin shell element model, also presents a correlation between computer predicted and actual experimental results for static deflection, natural frequencies and mode shapes of frame. A method to estimate the number of normal modes that are important is discussed.

• Structural Engineering and Mechanics
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• 제47권6호
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• pp.791-818
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• 2013

The seismic performance of reinforced concrete (RC) frame structures with irregularities leading to soft first floor is studied using capacity assessment procedures. The soft first story effect is investigated for the cases: (i) slab-column connections without beams at the first floor, (ii) tall first story height and (iii) pilotis type building (open ground story). The effects of the first floor irregularity on the RC frame structure performance stages at global and local level (limit states) are investigated. Assessment based on the Capacity Spectrum Method (ATC-40) and on the Coefficient Method (FEMA 356) is also examined. Results in terms of failure modes, capacity curves, interstory drifts, ductility requirements and infills behaviour are presented. From the results it can be deduced that the global capacity of the structures is decreased due to the considered first floor morphology irregularities in comparison to the capacities of the regular structure. An increase of the demands for interstory drift is observed at the first floor level due to the considered irregularities while the open ground floor structure (pilotis type) led to even higher values of interstory drift demands at the first story. In the cases of tall first story and slab-column connections without beams soft-story mechanisms have also been observed at the first floor. Rotational criteria (EC8-part3) showed that the structure with slab-column connections without beams exhibited the most critical response.

• Steel and Composite Structures
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• 제50권3호
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• pp.337-345
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• 2024

This research proposed a particle swarm optimization (PSO) based seismic retrofit design of moment frame structures using a steel frame assembly. Two full scale specimens of the steel frame assembly with different corner details were attached to one-story RC frames for seismic retrofit, and the lateral load resisting capacities of the retrofitted frames subjected to cyclic loads were compared with those of a bare RC frame. The open source software framework Opensees was used to develop an analytical model for validating the experimental results. The developed analytical model and the optimization scheme were applied to a case study structure for economic seismic retrofit design, and its seismic performance was assessed before and after the retrofit. The results show that the developed steel frame assembly was effective in increasing seismic load resisting capability of the structure, and the PSO algorithm could be applied as convenient optimization tool for seismic retrofit design of structures.

• Steel and Composite Structures
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• 제37권4호
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• pp.447-462
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• 2020

In this paper, a simplified seismic design method for low-rise dual frame-steel plate shear wall (SPSW) structures is proposed in the framework of performance-based seismic design. The dynamic response of a low-rise structure is mainly dominated by the first-mode and the structural system can be simplified to an equivalent single degree-of-freedom (SDOF) oscillator. The dual frame-SPSW structure was decomposed into a frame system and a SPSW system and they were simplified to an equivalent F-SDOF (SDOF for frame) oscillator and an equivalent S-SDOF (SDOF for SPSW) oscillator, respectively. The analytical models of F-SDOF and S-SDOF oscillators were constructed based on the OpenSees platform. The equivalent SDOF oscillator (D-SDOF, dual SDOF) for the frame-SPSW system was developed by combining the F-SDOF and S-SDOF oscillators in parallel. By employing the lateral force resistance coefficients and seismic demands of D-SDOF oscillator, the design approach of SPSW systems was developed. A 7-story frame-SPSW system was adopted to verify the feasibility and demonstrate the design process of the simplified method. The results also show the seismic demands derived by the equivalent dual SDOF oscillator have a good consistence with that by the frame-SPSW structure.

• 한국인터넷방송통신학회논문지
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• 제19권1호
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• pp.145-152
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• 2019

본 논문에서는 딥러닝을 활용한 흔들림 영상 안정화 알고리즘을 제안하였다. 제안하는 알고리즘은 기존 몇 가지 2D, 2.5D 및 3D 기반 안정화 기술과 다르게 딥러닝을 활용한다. 제안하는 알고리즘은 흔들리는 영상을 CNN 네트워크 구조와 LSTM 네트워크 구조를 통한 특징 추출 및 비교하여 이전 프레임과 현재 프레임 간의 특징점 위치 차이를 통해 특징점의 이동 크기와 방향의 반대로 영상을 변환하는 알고리즘이다. 흔들림 안정화를 위한 알고리즘은 각 프레임의 특징 추출 및 비교를 위해 Tensorflow를 활용하여 CNN 네트워크과 LSTM 구조를 구현하였으며, 영상 흔들림 안정화는 OpenCV open source를 활용해 구현하였다. 실험결과 영상의 흔들림이 상하좌우로 흔들리는 영상과, 급격한 카메라 이동이 없는 영상을 실험에 사용하여, 제안한 알고리즘을 적용한 결과 사용한 상하좌우 흔들림 영상에서는 안정적인 흔들림 안정화 성능을 기대할 수 있었다.

• Smart Structures and Systems
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• 제18권6호
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• pp.1189-1202
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• 2016

This paper describes an application of wavelet analysis for damage detection of a steel frame structure with bolted connections. The wavelet coefficients of the acceleration response for the healthy and loosened connection structure were calculated at each measurement point. The difference of the wavelet coefficients of the response of the healthy and loosened connection structure is selected as an indicator of the damage. At each node of structure the norm of the difference of the wavelet coefficients matrix is then calculated. The point for which the norm has the higher value is a candidate for location of the damage. The above procedure was experimentally verified on a laboratory-scale 2-meter-long steel frame. The structure consists of 11 steel beams forming a four-bay frame, which is subjected to impact loads using a modal hammer. The accelerations are measured at 20 different locations on the frame, including joints and beam elements. Two states of the structure are considered: healthy and damaged one. The damage is introduced by means of loosening two out of three bolts at one of the frame connections. Calculating the norm of the difference of the wavelet coefficients matrix at each node the higher value was found to be at the same location where the bolts were loosened. The presented experiment showed the effectiveness of the wavelet approach to damage detection of frame structures assembled using bolted connections.