• Steel and Composite Structures
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• 제4권6호
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• pp.419-435
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• 2004

The safety level of a structural system designed per code specifications can not be inferred directly from the reliability of members due to the load redistribution and nonlinear inelastic structural behavior. Comparison of the system and member reliability, which is scarce in the literature, is likely to indicate any possible inconsistency of design codes in providing safe and economical designs. Such a comparative study is presented in this study for moment resisting two-dimensional steel frames designed per AISC LRFD Specifications. The member reliability is evaluated using the resistance of the beam-column element and the elastic load effects that indirectly accounts for the second-order effects. The system reliability analysis is evaluated based on the collapse load factor obtained from a second-order inelastic analysis. Comparison of the system and member reliability is presented for several steel frames. Results suggest that the failure probability of the system is about one order of magnitude lower than that of the most critically loaded structural member, and that the difference between the system and member reliability depends on the structural configuration, degree of redundancy, and dead to live load ratio. Results also suggest that the system reliability is less sensitive to initial imperfections of the structure than the member reliability. Therefore, the system aspect should be incorporated in future design codes in order to achieve more reliability consistent designs.

• Earthquakes and Structures
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• 제14권6호
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• pp.599-614
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• 2018

This study focuses on the earthquake performance of two URM buildings having typical architectural configurations common for residential use constructed per pre-modern code in Albania. Both buildings are unreinforced clay brick masonry structures constructed in 1960 and 1984, respectively. The first building is a three-storey unreinforced one with masonry walls. The second one is confined masonry rising on five floors. Mechanical characteristics of masonry walls were determined based on experimental tests conducted according to ASTM C67-09 regulations. A global numerical model of the buildings was built, and masonry material was simulated as nonlinear. Pushover analyses are carried out to obtain capacity curves. Displacement demands were calculated according to Eurocode 8 and FEMA440 guidelines. Causes of building failures in recent earthquakes were examined using the results of this study. The results of the study showed that the URM building displays higher displacement and shear force demands that can be directly related to damage or collapse. On the other hand, the confined one exhibits relatively higher seismic resistance by indicating moderate damage. Moreover, effects of demand estimation approaches on performance assessment of URM buildings were compared. Deficiencies and possible solutions to improve the capacity of such buildings were discussed.

• 한국농촌건축학회논문집
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• 제21권2호
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• pp.35-42
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• 2019

There are 17,427 reservoirs in Korea, of which about 96% were built before the mid 1980s. Therefore, aging is severe and reinforcement are necessary. In addition, aged reservoirs, which are more than 50 years old, account for 70% of the total. Therefore, there is a problem such as the collapse of the reservoir and the decrease of the storage capacity due to progress of aging with time. The grouting method using cement is mainly used as maintenance and reinforcement method of old reservoir. However, the grouting method using cement has engineering and environmental problems. In order to solve the engineering and environmental problems of cement grouting method, an eco-friendly grouting material was developed that mixes circular resource grouting binder, high molar ratio sodium silicate and colloidal silica. The engineering and environmental properties of the developed injection materials were evaluated by conducting gel time, homo-gel strength, sea water resistance test and environmental stability evaluation. Also, examined the possibility of replacing OPC existing aged reservoir reinforcement methods. As a result, it was found out that it was better than the conventional cement method in terms of engineering and environment. However, since this study is the result of laboratory test, it is necessary of verify the application at field of aged reservoir.

• 동남아시아연구
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• 제22권2호
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• pp.171-199
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• 2012

Saman, a novel written by Ayu Utami, has been recognized as the symbol of the politico-social changes, which began to occur since the collapse of Suharto' New Order regime in 1998. In the novel, Ayu Utami showed the spirits of resistance against various absurd socio-political circumstances during the New Order era such as pressure on discussion, abuse of power, politics-business collusion, patriarchism, and suppression of gender. In representing those spirits, Ayu Utami used unconventional structure-making, fresh feedback and multilayered descriptions of the figures, which brought her a fame as the pioneer of the Fragrant Literature (Angkatan Wangi or chick-lit). Ayu Utami particularly criticized that, under the name of sustaining the national integrity and identity, the New Order regime enhanced patriarchal system, which consequently infringed gender equality and women's rights to self-determination. In addition, Ayu Utami argued that the abuse of power and politics-business collusion, which were prevalent during the New Order period, destroyed lives of the masses and the Indonesian society.

• Steel and Composite Structures
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• 제49권1호
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• pp.19-30
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• 2023

Steel-concrete composite slabs represent a very efficient floor solution combining the key performance of two different materials: the steel and the concrete. Composite slab response is governed by the degree of the interaction between these two materials, mainly depending by chemical and mechanical bond. The latter is characterized by a limited degree of confinement if compared with the one of the rebars in reinforced concrete members while the former is remarkably influenced by the type of concrete and the roughness of the profiled surface, frequently lubricated during the cold-forming manufacturing processes. Indeed, owing to the impossibility to guarantee a full interaction between the two materials, a key parameter governing slab design is represented by the horizontal shear-bond strength, which should be always experimentally estimated. According to EC4, the design of the slab bending resistance, is based on the simplified assumption that the decking sheet is totally yielded, i.e., always in plastic range, despite experimental and numerical researches demonstrate that a large part of the steel deck resists in elastic range when longitudinal shear collapse is achieved. In the paper, the limit strain for composite slab, which corresponds to the slip, i.e., the debonding between the two materials, has been appraised by means of a refined numerical method used for the simulation of experimental results obtained on 8 different composite slab types. In total, 71 specimens have been considered, differing for the properties of the materials, cross-section of the trapezoidal profiled metal sheets and specimen lengths.

• Geomechanics and Engineering
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• 제36권3호
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• pp.247-258
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• 2024

Tailings are waste materials of mining operations, consisting of a mixture of clay, silt, sand with a high content of unrecoverable metals, process water, and chemical reagents. They are usually discharged as slurry into the storage area retained by dams or earth embankments. Poor knowledge of the hydro-mechanical behaviour of tailings has often resulted in a high rate of failures in which static liquefaction has been widely recognized as one of the major causes of dam collapse. Many studies have dealt with the static liquefaction of coarse soils in saturated conditions. This research provides an extension to the case of silty tailings in unsaturated conditions. The static liquefaction resistance was evaluated in terms of stress-strain behavior by means of monotonic triaxial tests. Its dependency on the preparation method, the volumetric water content, the void ratio, and the degree of saturation was studied and compared with literature data. The static liquefaction response was proved to be dependent mainly on the preparation technique and degree of saturation that, in turn, controls the excess of pore pressure whose leading role is investigated by means of the relationship between the -B Skempton parameter and the degree of saturation. A preliminary interpretation of the static liquefaction response of Stava tailings is also provided within the Critical State framework.

• 콘크리트학회논문집
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• 제24권4호
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• pp.369-379
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• 2012

비산물체의 충돌 및 폭발, 테러 등의 극한하중에 의한 구조물의 붕괴는 재산상의 손실뿐만 아니라 다수의 인명피해를 유발한다. 일반적으로 콘크리트는 타 건설재료에 비해 충격 및 폭발 하중에 우수한 저항성능을 지니고 있다고 알려져 있으나, 준-정적(quasi-static)하중과는 달리 높은 변형률 속도를 갖는 극한하중을 고려하지 않고 설계된 기존의 콘크리트 구조물은 예상치 못한 극한하중에 노출될 경우 상당히 위험할 수 있다. 이 연구에서는 콘크리트 보의 충격저항성능을 향상시키기 위해 길이 30 mm의 번들형 양단 hooked type의 강섬유를 전체 부피의 0%에서 1.5%까지 혼입하여 정하중 및 충격하중 휨 실험을 수행하고, 그 성능을 평가하였다. 실험 결과 강섬유의 혼입률을 증가시킬 경우 정하중뿐만 아니라 충격하중에서도 휨강도와 연성 등 휨 저항성능이 크게 향상되는 경향을 보였다. 강섬유를 인장부에 집중적으로 혼입한 층 구조 콘크리트 보의 경우에는 동일한 양의 섬유를 보 전체에 타설한 시편에 비해 휨 저항성능이 향상되는 것으로 나타났다. 또한, 강섬유 보강 콘크리트의 재료적 비선형성을 고려하여 단자유도계(sing degree of freedom, SDOF) 시스템의 해석 알고리즘을 구성하고 실험 결과와 비교하였으며, 비교적 정확하게 최대 처짐을 예측하는 것으로 나타났다.

• 콘크리트학회논문집
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• 제28권6호
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• pp.673-683
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• 2016

최근 전 세계적으로 발생하고 있는 각종 사고 및 테러공격 등으로 인한 폭발, 충돌, 화재 사고가 빈번하게 발생하고 있으며, 특히, 2001년 미국 세계무역센터와 펜타곤에 발생한 9.11 테러사건 이후 사회적인 안전 불감증이 더욱 고조되고 있다. 또한, 2011년 일본 후쿠시마 원전사고로 인한 원전 격납건물 손상 시 발생할 수 있는 물리적, 환경적 위험성에 대한 사회적 불안감이 날로 커짐에 따라 원전격납건물, 가스탱크 등에 널리 사용되는 프리스트레스트 콘크리트 구조물에 대한 극한하중 연구가 다양하게 진행되고 있다. 본 연구에서는 2방향 비부착 프리스트레스트 콘크리트 패널 부재의 폭발저항성능을 분석하기 위하여 $1,400{\times}1,000{\times}300mm$의 철근콘크리트(RC), 프리스트레스 텐던으로만 보강된 콘크리트(PSC), 프리스트레스 텐던과 철근으로 보강된 콘크리트(PSRC) 시편을 제작하였다. 폭발하중은 ANFO 55 lbs 의 장약량을 1.0 m 이격거리로 적용하였으며, 측정하고자 하는 데이터는 초기 압력폭발하중 뿐 아니라, 반사압력, 충격량, 중앙부의 처짐, 가속도, 철근 및 콘크리트, 텐던의 변형률을 측정하여 분석하였다. 본 연구는 향후 국내외 프리스트레스트 콘크리트에 대한 방호설계 및 폭발해석 등 관련 연구분야의 중요한 자료가 될 것이라 판단된다.

• 해양환경안전학회지
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• 제29권5호
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• pp.488-496
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• 2023

선박 및 교량 구조물은 일종의 길이가 긴 박스형 구조로서 수직 굽힘 모멘트에 대한 저항력이 설계의 주요 인자이다. 특히 선박 거더는 반복적으로 불규칙적인 파랑하중에 장시간 노출되어 있기 때문에 구조부재의 연속 붕괴 거동을 정확하게 예측하는 것이 무엇보다도 중요하다. 본 논문에서는 순수 휨모멘트를 받는 박스거더의 하중 변화에 따른 좌굴을 포함한 소성 붕괴 거동을 수치해석적 방법을 이용하여 분석하였다. 분석대상은 Gordo 실험에서 사용한 세 가지 박스거더로 선정하였다. 구조강도 실험 결과와 비선형 유한요소해석에 의한 결과를 비교하여 차이가 발생하는 원인에 대해서 고찰하였다. 본 논문에서는 카본스틸 재료의 제작 시 필연적으로 사용하는 용접열에 의한 초기 처짐의 영향을 반영하기 위하여 전체와 국부적인 처짐 형상의 조합을 제안하였고, 이 결과는 실험 결과와 거동 및 최종강도 추정율이 7% 이내에서 잘 일치하고 있었다. 논문에서 검토한 절차 및 초기 처짐 구성에 대한 내용은 향후 유사 구조물의 최종강도를 분석하는데 좋은 지침으로 사용할 수 있다.

• 대한토목학회논문집
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• 제26권1A호
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• pp.11-19
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• 2006

본 연구에서는 현수교의 선박충돌해석을 위한 설계선박을 결정하기 위하여 선박충돌위험도해석을 수행한다. 선박충돌에 대한 설계선박을 결정하기 위하여 AASHTO 설계기준에서 제시한 3개의 선박충돌 설계방법 중 확률기반 해석방법인 Method II를 사용한다. 선박충돌 위험에 노출된 각각의 교각에 대해 선박충돌위험도 평가를 하여 교각의 충돌설계수평강도를 결정한다. 해석과정은 반복적인 것으로 교량부재의 충돌저항강도를 가정하고 연간파괴빈도를 계산하여 허용기준이 만족하도록 설계 변수를 수정한다. 허용기준은 예상연간파괴빈도에 근거한 가중치를 이용하여 교각에 할당한다. 해석결과에서 안전성과 경제성을 얻기 위해 이 할당방법을 주탑집중 할당방법과 비교한다. 비록 주탑집중 할당방법이 주탑에 비해 과대평가되는 교각의 설계수평강도를 적절히 수정할 경우 보다 경제적인 결과를 가져오지만, 가중치에 의한 할당방법이 설계인자의 특성을 정량적으로 고려하기 때문에 더 합리적인 것으로 보인다. 그리고 선박충돌위험도 평가로부터 얻어지는 충돌설계수평강도에 상응하는 각각의 교각에 대한 설계선박이 결정된다. 같은 교량에 대해서도 충돌설계수평강도가 수로 및 교량의 특성과 선박통행량에 따라 상당히 변화한다. 따라서 허용기준의 할당과 설계선박 선정에 대한 많은 연구가 요구된다.