• Structural Engineering and Mechanics
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• 제46권2호
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• pp.213-229
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• 2013

Although performance based assessment procedures are mainly developed for reinforced concrete and steel buildings, URM (Unreinforced Masonry) buildings occupy significant portion of buildings in earthquake prone areas of the world as well as in IRAN. Variability of material properties, non-engineered nature of the construction and difficulties in structural analysis of masonry walls make analysis of URM buildings challenging. Despite sophisticated finite element models satisfy the modeling requirements, extensive experimental data for definition of material behavior and high computational resources are needed. Recently, nonlinear equivalent frame models which are developed assigning lumped plastic hinges to isotropic and homogenous equivalent frame elements are used for nonlinear modeling of URM buildings. The equivalent frame models are not novel for the analysis of masonry structures, but the actual potentialities have not yet been completely studied, particularly for non-linear applications. In the present paper an effective tool for the non-linear static analysis of 2D masonry walls is presented. The work presented in this study is about performance assessment of unreinforced brick masonry buildings through nonlinear equivalent frame modeling technique. Reliability of the proposed models is tested with a reversed cyclic experiment conducted on a full scale, two-story URM building at the University of Pavia. The pushover curves were found to provide good agreement with the experimental backbone curves. Furthermore, the results of analysis show that EFM (Equivalent Frame Model) with Dolce RO (rigid offset zone) and shell element have good agreement with finite element software and experimental results.

• 전자공학회논문지A
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• 제33A권10호
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• pp.40-47
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• 1996

A method for computing effectiv ebandwidth of aggregated varable bit rate (VBR) moving picture experts group (MPEG) video traffic is proposed. To compute statistical characteristics of aggregated MPEG traffic, first we split input MPEG traffic into I, B, and P frame traffics and aggregate respective I, B, and P frame traffics according to the frame type. Second statisticsal characteristics of the aggregated MPEG traffic are obtained using those of aggregated I, B, and P frame traffics. The effective bandwidth of the aggregated I frame traffic is computed by using the gaussian bound. Using the modified equivalent capacity, we obtain the effective bandwidths of aggregated B and P frame traffics and then compute the effective bandwidth of the combined B and P frame traffic. Finally the effective bandwidth of the aggregated MPEG traffic is computed by adding the gaussian bound of the aggregated I frame traffic and modifed equivalent capacity of combined B and P frame traffic. Computer simulation shows that the proposed method estimates effective bandwidth of the aggregated MPEG traffic well.

• 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.

• 한국자동차공학회논문집
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• 제12권3호
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• pp.91-100
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• 2004

This study presents the development of a new aluminum seat frame for the commercial bus. Back moment and seat belt anchorage analysis of the conventional steel seat frame was conducted as a base model. Effective aluminum section dimensions for aluminum pipe were calculated from equivalent stiffness and equivalent weight study. Back moment and seat belt anchorage strength with the developed aluminum seat frame were compared to those of the base model. Additionally, to pass the fatigue test, shape modification of side frame assembly was conducted. From this study we could reduce the weight of seat frame more than 5 kg. And the current analysis model and procedure can provide useful informations in designing a new commercial car seat and can reduce the overall design cost and time.

• Steel and Composite Structures
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• 제19권5호
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• pp.1055-1075
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• 2015

In order to investigate the accuracy and applicability of steel equivalent constitutive model, the calculated results were compared with typical tests of steel frames under static and dynamic loading patterns firstly. Secondly, four widely used models for time history analysis of steel frames were compared to discuss the applicability and efficiency of different methods, including shell element model, multi-scale model, equivalent constitutive model (ECM) and traditional beam element model (especially bilinear model). Four-story steel frame models of above-mentioned finite element methods were established. The structural deformation, failure modes and the computational efficiency of different models were compared. Finally, the equivalent constitutive model was applied in seismic incremental dynamic analysis of a ten-floor steel frame and compared with the cyclic hardening model without considering damage and degradation. Meanwhile, the effects of damage and degradation on the seismic performance of steel frame were discussed in depth. The analysis results showed that: damages would lead to larger deformations. Therefore, when the calculated results of steel structures subjected to rare earthquake without considering damage were close to the collapse limit, the actual story drift of structure might already exceed the limit, leading to a certain security risk. ECM could simulate the damage and degradation behaviors of steel structures more accurately, and improve the calculation accuracy of traditional beam element model with acceptable computational efficiency.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
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• pp.272-275
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• 2004

This study is to propose a modified equivalent frame method under lateral loading. ACI 318-02 allows the equivalent frame method to conduct slab analysis subjected to lateral loads. However, current method can not predict the behavior of the slabs particularly under lateral loading because the equivalent frame method in the ACI 318 has been developed against gravity loads. This study provides more precise model for the analysis of the flat plate slabs under lateral loading. The model reflect the force transfer mechanism of slabs, column and torsional member more accurately than the existing model. The accuracy of this model is verified by compared with finite element method analysis results.

• Earthquakes and Structures
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• 제7권5호
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• pp.719-733
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• 2014

The equivalent frame method (EFM) is widely used for the design of two-way reinforced concrete slab structures, and current design codes of practice permit the application of the EFM in analyzing the flat plate slab structures under gravity and lateral loads. The EFM was, however, originally developed for the flat plate structures subjected to gravity load, which is not suitable for lateral loading case. Therefore, this study, the first part of series research paper, proposed the structural analysis method for the flat plate slab structures under the combined gravity and lateral loads, which is named as the unified equivalent frame method (UEFM). In the proposed method, some portion of rotation induced in the torsional member is distributed to the flexibility of the equivalent columns, and the remaining portion is contributed to that of the equivalent slabs. In the consecutive companion paper, the proposed UEFM is verified by comparing with test results of multi-span flat plate structures. Also, a simplified nonlinear push-over analysis method is proposed, and verified by comparing to test results.

• 콘크리트학회논문집
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• 제17권3호
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• pp.419-426
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• 2005

본 연구는 수평하중을 받는 플랫 플레이트 슬래브 해석을 위한 수정된 등가골조 모델을 제안한 것이다. ACI 318 (2000)은 중력하중 뿐만 아니라 수평하중을 받는 2 방향 슬래브 해석을 위해 등가골조 모델을 허용하고 있다. ACI 318 (2000)에서 채택하고 있는 등가골조 모델은 중력하중을 고려하여 발전되었기 때문에, 수평하중하의 플랫 플레이트 슬래브의 거동을 정확하게 예측하지 못할지 모른다. 따라서 본 연구는 수평하중 하의 플랫 플레이트 슬래브에 대한 더 정확한 해답을 줄 수 있는 수정된 등가골조 모델을 발전시켰다. 수평하중이 지배적인 경우, 이 모델은 기존 등가골조 모델보다 플랫 플레이트 슬래브 시스템의 구성요소 슬래브, 기둥, 비틀림 부재에 대한 더 정확한 힘의 전달 메커니즘을 반영한다. 이 모델의 타당성은 유한요소해석 결과와 제안한 모델의 해석 결과를 비교하여 검증하였으며, 기존 등가골조 모델의 해석 결과가 비교에 포함되었다. 양방향으로 3스팬을 갖는 2층 건물을 비교 대상으로 삼았으며, 수정된 등가골조 모델의 수평변위 및 슬래브모멘트 결과는 유한요소해석 결과와 가장 근사한 결과를 나타냈다.

• Structural Engineering and Mechanics
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• 제68권5호
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• pp.621-632
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• 2018

Soft-story buildings have bottom stories much less rigid than the top stories and are susceptible to earthquake damage. Therefore, the seismic design specifications need strict design considerations in such cases. In this paper, a four-story building was investigated as a case study and the effects of X-braces elimination in its lower stories studied. In addition, the possibility of replacement of the X-braces in soft-stories with equivalent moment resisting frame inspected in two different phases. In first phase, the stiffness of X-braces and equivalent moment-resisting frames evaluated using classic equations. In final phase, diagonals removed from the lowest story to develop a soft-story and replaced with moment resisting frames. Then, the seismic stiffness variation of moment-resisting frame evaluated using nonlinear static and dynamic analyses. The results show that substitution of braced frames with an equivalent moment-resisting frame of the same stiffness increases story drift and reduces energy absorption capacity. However, it is enough to consider the needs of building codes, even using equivalent moment resisting frame instead of X-Braces, to avoid soft-story stiffness irregularity in seismic design of buildings. Besides, soft-story development in the second story may be more critical under strong ground excitations, because of interaction of adjacent stories.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.369-372
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• 2006

Flat plate slab systems have been commonly used as a gravity force resisting systems, which should be constructed with lateral force resisting systems such as shear walls and moment resisting frame. ACI 318(2005) allows the Direct design method, the equivalent frame method (ACI-EFM) under gravity loads and the finite-element models, effective beam width models and equivalent frame models under lateral loads. ACI-EFM can be used for gravity loads as well as lateral loads analysis. But the method may not predict the behavior of flat plate slabs under lateral loads. Thus Previous study developed a Modified equivalent frame method(Modified-EFM) which could give more precise answer for flat plate slab under lateral loads. This study is to verified the accuracy of a Modified-EFM under combined lateral and gravity loads. The accuracy of this model is verified by comparing the results using the Modified-EFM with the results of finite element analysis. For this purpose, 7 story building is considered. The analysis results of other existing models are included. The analysis results show that Modified-EFM produces comparable drift and slab internal moments with those obtained from finite element analysis.