• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1990년도 가을 학술발표회 논문집
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• pp.73-78
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• 1990

In current practice of earthquake resistant design the equivalent lateral force procedure is widely used for its simplicity and convenience. But the equivalent lateral force procedure is derived based on the assumption that the dynamic behavior of the structure is governed primarily by the fundamental vibration mode. Therefore proper prediction of dynamic responses of the structure is unreliable using the equivalent lateral force procedure when the effect of higher vibration modes on the dynamic behavior is negligible. In this study design seismic load which can reflect the effect of higher vibration modes is proposed from the point of view of proper assessment of story shears which have the major influence on the design moment of beams and columns. To evaluate the effect of higher modes, differences between the story force based on the equivalent lateral force procedure specified in current earthquake resistance building code and the one based on modal analysis using design spectrum are examined. From these results improved design seismic load for the equivalent lateral force procedure which can reflect the effect of higher vibration modes is proposed.

• 전산구조공학
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• 제3권4호
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• pp.123-132
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• 1990

일반적으로 구조물의 내진설계에 있어서는 등가정적해석법이 주로 사용되고 있다. 현재 사용되고 있는 등가정적해석법은 구조물의 거동이 주로 기본진동 모드에 의해 지배된다는 가정하에 유도되었으므로 기본진동 주기가 긴 구조물에 대해서는 구조물의 동적특성을 정확하게 예측하기가 어렵다. 본 연구에서는 구조물의 설계시 직접적인 영향을 미치게 되는 층전단력의 분포를 주요 관점으로하여 구조물의 동적특성에 미치는 고차모드의 영향을 정확히 고려할 수 있는 층지진하중에 대하여 연구했다. 층지진하중의 분포를 개선하기 위해 현행 내진설계 기준의 등가정적해석법에서 쓰이는 층지진하중과 모드해석을 이용하여 얻은 층지진하중의 차이를 파악하고 이로부터 고차모드의 영향이 고려된 층지진하중의 분포를 제안했다.

• 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.

• 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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• 제4권6호
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• pp.685-710
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• 2013

Static torsional provisions employing equivalent lateral force method (ELF) require that the earthquake-induced lateral force at each story be applied at a distance equal to design eccentricity ($e_d$) from a reference resistance centre of the corresponding story. Such code torsional provisions, albeit not explicitly stated, are generally believed to be applicable to the regularly asymmetric buildings. Examined herein is the applicability of such code-torsional provisions to buildings with set-back using rigid as well as flexible diaphragm model. Response of a number of set-back systems computed through ELF with static torsional provisions is compared to that by response spectrum based procedure. Influence of infill wall with a range of opening is also investigated. Results of comprehensive parametric studies suggest that the ELF may, with rational engineering judgment, be used for practical purposes taking some care of the surroundings of the setback for stiff systems in particular.

• Structural Engineering and Mechanics
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• 제21권4호
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• pp.469-494
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• 2005

In order to consider the modified seismic response of framed structures in the presence of masonry infills, proper models have to be formulated. Because of the complexity of the problem, a careful definition of an equivalent diagonal pin-jointed strut, able to represent the horizontal force-interstorey displacement cyclic law of the actual infill, may be a solution. In this connection the present paper, continuing a previous work in which a generalised criterion for the determination of the ideal cross-section of the equivalent strut was formulated, analizes some models known in literature for the prediction of the lateral cyclic behaviour discussing their field of validity. As a support of the discussion, the results of an experimental investigation involving single story-single bay infilled reinforced concrete. Frames under vertical and lateral loads with different kind of infill (actually not yet so much investigated) are presented. Finally, an improvement of a model known in the literature is proposed, taking the results of the experimental tests before mentioned into account.

• Structural Engineering and Mechanics
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• 제4권5호
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• pp.497-511
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• 1996

The equivalent static force procedure and the response spectrum analysis method are widely used for seismic analyses of multi-story buildings. The equivalent static force procedure is one of the most simple but less accurate method in predicting possible seismic response of a structure. The response spectrum analysis method provides more accurate results while it takes much longer computational time. In the response spectrum method, dynamic response of a multi-story building is obtained by combining modal responses through a proper procedure such as SRSS or CQC method. Since all of the analysis results are expressed in absolute values, structural engineers have difficulties to combine them with the results obtained from the static analysis. Design automation is interrupted at this stage because of the difficulty in the decision of the most critical design load. Pseudo-dynamic analysis method proposed in this study provides more accurate seismic analysis results than those of the equivalent static force procedure since the dynamic characteristics of a structure is considered. And the proposed method has an advantage in combination of the analysis results due to gravity loads and seismic loads since the direction of the forces can be considered.

• 한국강구조학회 논문집
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• 제13권2호
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• pp.201-210
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• 2001

본 연구에서는 편심 축력을 받는 가셋트-강관 접합부의 극한 내력을 파악하기 위하여 실험 및 유한요소해석을 수행하였다. 가셋트-강관 접합부의 내력에 영향을 주는 요소는 강관의 직경, 가셋트판 길이, 축력과 횡력의 비, 횡력에 의한 편심 등으로 이들이 주재의 좌굴내력에 미치는 영향을 정량적으로 파악하여 접합부 강도식을 제안하였다. 특히 횡력에 의한 편심이 주재에 작용할 때 이를 설계식에 반영하기 위하여 횡력을 등가의 모멘트 및 편심 축력으로 대치한 수치 모형을 제시하였다. 결과적으로 접합부의 작용하는 외력을 주주재 축력, 모멘트, 편심 축력으로 분해하고 각 외력에 대한 독립적인 극한내력을 구한후 이들의 상관 관계식을 구함으로써 접합부 극한강도식을 제시하였다.

• 한국지진공학회논문집
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• 제24권6호
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• pp.243-251
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• 2020

In seismic design standards such as KDS 41 17 00 and ASCE 7, three procedures are provided to estimate seismic demands: equivalent lateral force (ELF), response spectrum analysis (RSA), and response history analysis (RHA). In this study, two steel special moment frames (SMFs) were designed with ELF and RSA, which have been commonly used in engineering practice. The collapse probabilities of the SMFs were evaluated according to FEMA P695 methodology. It was observed that collapse probabilities varied significantly in accordance with analysis procedures. SMFs designed with RSA (RSA-SMFs) had a higher probability of collapse than SMFs designed with ELF (ELF-SMFs). Furthermore, RSA-SMFs did not satisfy the target collapse probability specified in ASCE 7-16 whereas ELF-SMFs met the target probability.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1993년도 가을 학술발표회 논문집
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• pp.267-272
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• 1993

Currently about 60 contries in the world require earthquake resistant structural design in case of multistory building constructions. In these cases the equivalent lateral force procedure is commonly adopted because of its simplicity and convenience. This procedure, however, is developed based mainly on the first vibration mode response of building structure. The dynamic analysis of tall building shows that the effect of higher modes of vibration on the response of the building can not be neglected. In this paper, the effect of higher modes of vibration on seismic response is evaluated through modal analysis of tall building structures. On the basis of evaluation results, an improved procedure is to be proposed for the extended application of the equivalent lateral force procedure.