• Structural Engineering and Mechanics
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• 제36권3호
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• pp.301-319
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• 2010

The paper seeks to explore some aspects of the current state of knowledge on progressive collapse in the technical literature covering blast loads and structural analysis procedure applicable to reinforced concrete (RC) buildings. The paper describes the progressive collapse analysis of a commercial RC building located in the city of Riyadh and subjected to different blast scenarios. A 3-D finite element model of the structure was created using LS-DYNA, which uses explicit time integration algorithms for solution. Blast loads were treated as dynamic pressure-time history curves applied to the exterior elements. The inherent shortcomings of notional member removal have been taken care of in the present paper by simulating the damage of structural elements through the use of solid elements with the provision of element erosion. Effects of erosion and cratering are studied for different scenarios of the blast.

• Earthquakes and Structures
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• 제6권5호
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• pp.515-537
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• 2014

Current seismic codes (e.g. the NTC08 Italian code and the EC8 European code) adopt a performance-based approach for both the design of new buildings and the assessment of existing ones. Different limit states are considered by verifying structural members as well as non structural elements and facilities which have generally been neglected in practice. The key role of non structural elements on building performance has been shown by recent earthquakes (e.g. L'Aquila 2009) where, due to the extensive damage suffered by infills, partitions and ceilings, a lot of private and public buildings became unusable with consequent significant socio-economic effects. Furthermore, the collapse of infill panels, particularly in the case of out-of-plane failure, represented a serious source of risk to life safety. This paper puts forward an infill model capable of accounting for the effects arising from prior in-plane damage on the out-of-plane capacity of infill panels. It permits an assessment of the seismic performance of existing RC buildings with reference to both structural and non structural elements, as well as of their mutual interaction. The model is applied to a building type with RC framed structure designed only to vertical loads and representative of typical Italian buildings. The influence of infill on building performance and the role of the out-of-plane response on structural response are also discussed.

• Structural Engineering and Mechanics
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• 제71권4호
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• pp.417-432
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• 2019

Seismic performance analysis of steel-brace reinforced concrete (RC) frame using topology optimization in highly seismic region was discussed in this research. Topology optimization based on truss-like material model was used, which was to minimum volume in full-stress method. Optimized bracing systems of low-rise, mid-rise and high-rise RC frames were established, and optimized bracing systems of substructure were also gained under different constraint conditions. Thereafter, different structure models based on optimized bracing systems were proposed and applied. Last, structural strength, structural stiffness, structural ductility, collapse resistant capacity, collapse probability and demolition probability were studied. Moreover, the brace buckling was discussed. The results show that bracing system of RC frame could be derived using topology optimization, and bracing system based on truss-like model could help to resolve numerical instabilities. Bracing system of topology optimization was more effective to enhance structural stiffness and strength, especially in mid-rise and high-rise frames. Moreover, bracing system of topology optimization contributes to increase collapse resistant capacity, as well as reduces collapse probability and accumulated demolition probability. However, brace buckling might weaken beneficial effects.

• Earthquakes and Structures
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• 제25권5호
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• pp.385-398
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• 2023

The parameters of the multiple-vertical-line-element model (MVLEM) of reinforced concrete (RC) shear walls are often empirically determined, which causes large simulation errors. To improve the simulation accuracy of the MVLEM for RC shear walls, this paper proposed a novel method to determine the MVLEM parameters using the artificial neural network (ANN). First, a comprehensive database containing 193 shear wall specimens with complete parameter information was established. And the shear walls were simulated using the classic MVLEM. The average simulation errors of the lateral force and drift of the peak and ultimate points on the skeleton curves were approximately 18%. Second, the MVLEM parameters were manually optimized to minimize the simulation error and the optimal MVLEM parameters were used as the label data of the training of the ANN. Then, the trained ANN was used to generate the MVLEM parameters of the collected shear walls. The results show that the simulation error of the predicted MVLEM was reduced to less than 13% from the original 18%. Particularly, the responses generated by the predicted MVLEM are more identical to the experimental results for the testing set, which contains both flexure-control and shear-control shear wall specimens. It indicates that establishing MVLEM for RC shear walls using ANN is feasible and promising, and that the predicted MVLEM substantially improves the simulation accuracy.

• Advances in concrete construction
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• 제17권4호
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• pp.221-232
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• 2024

As a supplemental energy dissipation device, friction dampers are widely employed to augment the behaviour of buildings under seismic forces. In the current work, a methodology for the design of the friction damping system of RC frame buildings is offered using performance-based plastic design (PBPD) method. Here 2% of maximum interstorey drift ratio for life safety (LS) level is taken into account as a target drift to estimate the design base shear. In this approach, the distribution of friction damper is determined based on the hysteretic energy demand of that storey. Two frames, five storey three bay (5S3B) and eight storey three bay (8S3B) RC frame building with and without friction damping systems are also taken up for the investigation. The suggested design approach is validated by the nonlinear time history analysis (NLTHA) procedure. Inter story drift ratio (ISDR) and storey displacement, which are the more closely related to structural damage during seismic excitation are evaluated. The results show that the friction damping system on a retrofitted RC frame building performs effectively under seismic excitations and that storey displacement and ISDR are within the limit at moderate and high seismic intensities.

• Structural Engineering and Mechanics
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• 제76권3호
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• pp.421-433
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• 2020

Masonry infills are normally considered as non-structural elements in design practice, therefore, the interaction between the bounding frame and the strength contribution of masonry infills is commonly ignored in the seismic analysis work of the RC frames. However, a number of typical RC frames with irregular distributed masonry infills have suffered from undesirable weak-story failure in major earthquakes, which indicates that ignoring the influence of masonry infills may cause great seismic collapse risk of RC frames. This paper presented the investigation on the risk of seismic collapse of RC frames with irregularly distributed masonry infills through a large number of nonlinear time history analyses (NTHAs). Based on the results of NTHAs, seismic fragility curves were developed for RC frames with various distribution patterns of masonry infills. It was found that the existence of masonry infills generally reduces the collapse risk of the RC frames under both frequent happened and very strong earthquakes, however, the severe irregular distribution of masonry infills, such as open ground story scenario, results in great risk of forming a weak story failure. The strong-column weak-beam (SCWB) ratio has been widely adopted in major seismic design codes to control the potential of weak story failures, where a SCWB ratio value about 1.2 is generally accepted as the lower limit. In this study, the effect of SCWB ratio on inter-story drift distribution was also parametrically investigated. It showed that improving the SCWB ratio of the RC frames with irregularly distributed masonry infills can reduce inter-story drift concentration index under earthquakes, therefore, prevent weak story failures. To achieve the same drift concentration index limit of the bare RC frame with SCWB ratio of about 1.2, which is specified in ACI318-14, the SCWB ratio of masonry-infilled RC frames should be no less than 1.5. For the open ground story scenario, this value can be as high as 1.8.

• 토지주택연구
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• 제2권2호
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• pp.195-204
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• 2011

철근콘크리트 건축물에 중장비를 탑재하여 해체작업을 시행할 때, 중장비와 철거잔재의 중량은 건축물을 설계할 당시에 고려하지 못한 하중으로 작용한다. 그러나 우리나라 해체 현장에서는 건축물의 안전성에 대한 구조전문가의 검토 없이, 현장 관리자나 작업자의 경험에 의하여 중장비 탑재와 해체작업이 이루어지고 있어 작업 중에 건축물이 붕괴하거나 중장비가 추락하는 사례도 발생하고 있다. 따라서 해체공사 시행 과정에서 해체 대상 건축물의 구조안전성을 평가할 수 있는 평가기법과 구조부재가 부담할 수 있는 적정 장비중량에 대한 기준 마련이 시급한 실정이다. 이 논문에서는 기계해체 현장에 대한 방문조사와 작업근로자에 대한 설문조사를 통해 해체 대상 건축물의 안전성 평가에 필요한 철거잔재 하중, 하중계수, 강도감소계수, 작업하중 등을 제안하였다. 해체 현황을 고려한 구조물의 해석과 부재(슬래브, 보)의 적절한 안전성 평가방법을 제시하였으며, RC 슬래브와 RC 보의 제원에 따라 양중 가능한 중장비의 중량을 제시하였다. 이 연구에서 제안한 해체구조물의 안전성 평가기법과 중장비 탑재 등급은 해체대상 구조부재의 성능을 합리적으로 평가하고, 적정한 장비운영을 통한 해체작업의 효율성과 안전성을 향상하는 데 유용하게 활용될 수 있을 것으로 사료된다.

• 한국전산구조공학회논문집
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• 제23권5호
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• pp.501-507
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• 2010

본 논문에서는 중력하중 및 풍하중, 지진하중을 받는 지상 8층, 지하 3층의 RC(Reinforced Concrete) 빌딩 시공에 필요한 부재의 재료비를 줄이기 위해 중량을 감소시키는 구조 최적설계를 수행한다. 이를 위해 설계요구사항을 바탕으로 부재의 부피를 최소화하는 설계변수값을 찾기 위한 설계문제를 정식화한다. 최적설계 수행을 위해 상용 PIDO(Process Integration and Design Optimization) 툴인 PIAnO(Process Integration, Automation and Optimization)에서 제공하는 다양한 설계기법들을 이용한다. 먼저 실험계획법(Design of Experiments; DOE)을 이용하여 실험계획을 세우고, 실험점에 따라 건축분야 범용 구조해석 프로그램인 MIDAS Gen을 사용하여 구조해석을 수행한다. 그리고 해석결과를 바탕으로 각 응답에 대한 근사모델을 생성한 후 근사모델의 예측성능을 평가한다. 예측성능이 검증된 근사모델과 최적화기법을 이용하여 최적설계를 수행하고, 설계조건을 만족하면서 부재의 부피를 최소화하는 최적 설계변수값을 도출함으로서 본 논문에서 제안된 설계방법의 유효성을 보이고자 한다.

• 한국구조물진단유지관리공학회 논문집
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• 제24권4호
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• pp.38-47
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• 2020

RC 고층건물에서 발생하는 기둥축소의 예측 오차를 최소화하기 위하여 계측결과를 이용한 해석보정에 대한 변수연구가 수행되었다. 해석보정의 변수는 해석보정 시행기준, 해석보정 값, 계측 위치이며, 변수에 따른 해석보정 모델을 41층 규모의 RC 건물의 시공단계해석에서 적용하여 변수에 따른 보정 효과를 비교·분석하였다. 보정 횟수와 전체 보정량에 따른 층별 오차 값의 감소율을 비교하였으며, 해석보정의 시행기준은 일정한 간격을 기준으로 해석보정 할 경우, 해석보정 값은 오차 값만큼 보정할 경우, 계측 위치는 매 층 계측이 될 경우에 오차가 최소화되는 경향을 확인하였다. 이로부터 실제 해석 모델에 대하여 여러 해석보정 모델을 적용함으로써 가장 적합한 해석보정 모델을 도출할 수 있음을 확인하였다.

• 국제초고층학회논문집
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• 제10권3호
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• pp.243-250
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• 2021

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